EP0276284A1 - Method of thermally processing foodstuffs - Google Patents

Abstract

Thermally processing seafood, e.g. shrimp, is performed in the presence of a mixture of an acid and its lactones, preferably a mixture of an aldonic acid and its lactones whereby, without need for salt, the texture and flavor of the seafood are maintained through thermal processing and storage. The preferred mixture is obtained by combining the seafood with glucono-delta lactone, and the mixture is comprised of gluconic acid with its lactones, glucono-delta lactone and glucono-gamma lactone.

Description

METHOD OF THERMALLY PROCESSING FOODSTUFFS

FIELD OF THE INVENTION This invention relates generally to the thermal processing of acid foodstuffs, low acid foodstuffs, or seafood and is particularly related to thermally processed, acid heat- sensitive foodstuffs such as tomatoes, fruits, and berries, low acid heat-sensitive vegetables, shrimp, sardines, and salmon. By "thermal processing" is meant subjecting the foodstuff to a time-temperature parameter which results in a "commercially sterilized" food, as defined in Title 21 CFR Part 113 (Definitions, Sec. 113.3) "Commercial sterility of thermally processed food means the condition achieved — "(i) By the application of heat which renders the food free of — "(a) Microorganisms capable of reproducing in the food under normal nonrefrigerated conditions of storage and distribution; and "(b) Viable microorganisms (including spores) of public health significance; or "(ii) By the control of water activity and the application of heat, which render the food free of microorganisms capable of reproducing in the food under normal nonrefrigerated condi¬ tions of storage and distribution." By "low acid" is meant the product in its natural state has an equilibrium pH greater than 4.6, and by "acid" it is meant that the product in its natural state has an equilibrium pH equal to or less than 4.6, more particularly less than 4.6. BACKGROUND AND OBJECTS OF THE INVENTION There are certain foods, particularly low-acid vegetables (some of which are hereinafter enumerated) which require thermal processing for a long period of time at a relatively high temperature (protracted time-temperature processing parameter) in order to kill microorganisms responsible for food spoilage and toxicity. Clostridium botulinum. for example, produces its lethal toxin only when it has achieved the vegetative form growing under anaerobic conditions in the canned food and this possibility is prevented by the sterilizing process.

Such prolonged processing can literally ruin the texture (material consistency, integrity and firmness) and color of certain heat-sensitive vegetables such as cauliflower and melons, neither of which is presently sold in the canned form, and with respect to other of the more heat-sensitive vegetables such as sliced squash, such prolonged processing renders their texture so soft and so affects their color as to tend to render them unattractive and unappealing to many consumers. These latter processed products presently are not accepted on a general consumer level and therefore are not canned on any significant commercial scale. The vegetables just named are only part of the entire list falling into the heat sensitive category By "heat-sensitive" is meant those food products which tend to degrade to the point where their texture, color and/or flavor is impaired when conventionally thermally processed.

From the moment of harvest, food undergoes progressive deterioration and preventative measures are often taken to prolong storage life. Food preservation techniques should retain the nutritional value and prolong the stability of the foods*^* organoleptic properties. By this is meant those properties or qualities of the foodstuff determinable by use of one or more of the human sense organs, the organoleptic qualities including texture, color, flavor and/or aroma.

Methods of preservation involve the application of scientific and engineering principles to control food deterioration. Modern processes to achieve food preservation are aimed primarily at controlling the growth of microorganisms. The most important means of controlling these microorganisms include heat, cold, drying, acids, sugar, salt, smoke, and curing. The following discussion will briefly describe each of these processes with the corresponding advantages and disadvantages.

Drying is one of the oldest methods of food preservation known to man. Sun drying of fruits, nuts and grains, meats and vegetables is an important method of food preservation. However, since the natural elements are unpredictable. mechanical dehydration equipment is used to maximize heat transfer into the product and afford greater control of the drying variables. Commercially used dried foods include apples, apricots, figs, prunes, raisins, carrots, potatoes, bananas, eggs, and milk. Most dried foods have excellent shelf life and are reasonably inexpensive and, because of convenience, have widespread use in the food service industry.

By freezing a product and drying it under high vacuum conditions, it is possible to produce many dried foods of superior quality than obtained with conventional drying. Freeze drying is currently used for selected fruits and vegetables, shrimp, coffee, and special military rations. However, they are very expensive, costing much more than conventional dried foods and frozen or canned foods.

A food concentrated to 65% or more soluble solids (largely composed of sucrose and other sugars) , may be preserved by mild heat treatment provided the food is protected from the air. Examples are syrups, jams, jellies, preserves, and sweetened condensed milk. However, due to the high sugar content the preservation of foods by this method is not applicable to most foods in the human diet. Two types of such mild heat treatment are pasteurization which involves a low heat of about 130°F to 155°F which alone does not commercially sterilize but must be combined with a food preservative or preservation system, and hot filling which involves filling a container with a food product heated at about 180oF to 212oF which can only commercially sterilize certain limited high acid or high sugar foods.

When used in sufficient quantity, salt has a bacteriostatic effect by creating an environment not conducive to bacterial growth. Salt is used, to a very limited extent, for preserving fish and meat, many times with the addition of smoke, to produce a drying effect and impart a desirable flavor. In the amounts necessary to inhibit bacterial growth, salt imparts a harsh, dry, salty taste that is not very palatable, has health implications and is objectionable to many consumers.

Smoke from burning wood contains traces of formaldehyde and other chemicals unfavorable to microorganisms. In addition, smoke is generally associated with a mild heat treatment, usually effected at from about 120°F to about 160°F and the resulting dehydration of the food (meat and fish) , contributes to its preservation. The resultant product is very dry and not very palatable. Currently, smoke is primarily used for flavor rather than preservation.

Curing is a process which involves chemically treating a meat foodstuff for preservation. While salt is basic to all mixtures for curing meat (bacon, ham, sausage, etc.) sodium nitrate and sodium nitrite have been used as part of the cure for centuries to stabilize the red color and inhibit growth of a number of food poisoning and spoilage organisms. Salts of ascorbic acid and erythorbic acid, and glucono-delta lactone (the lactone hydrolyzes to gluconic acid) are used to hasten development of and to stabilize the red color of red meat. Modern day methods of manufacturing cured meat products include mixing the curing salts with the raw ground meat emulsion (luncheon meat, sausage, etc.) or pumping the curing solution into the raw meat (ham, bacon, etc.) followed by cooking in hot water (150°F-165°F) to obtain an internal product temperature between 140°F to 155°F. These mild cures currently used are not sufficient to produce shelf stable meat products and therefore the meat must be kept under refrigeration.

Microorganisms are sensitive to acids in various degrees. The preserving effect of acid is due to the hydrogen ion concentration and its destabilization effect on bacterial cells. Acids may be found in foods as a natural component, produced in foods by fermentation, or added to foods directly as a chemical. Since acid enhances the lethality of heat, acid foods (pH 4.6 or below) need only be heated generally up to about 205oF which is much lower than the heat needed for more alkaline foods-(low acid; pH above 4.6) to render them free of spoilage organisms. The acids commonly added to foods (acetic, citric, malic) create a distinct "-pickled" flavor, which in many instances detracts from the natural home-cooked flavor and the foods to which they have been added are technically termed acidified.

Although not a sterilization process, low temperatures_c (0°F or below) inhibit bacterial growth and enable frozen foods to be stored for several months with very little deterioration of quality or loss of nutrients. Most meats, fish, vegetables and fruits freeze well and have high organoleptic qualities. It is generally recognized that quick-frozen foods retain the color, texture, and flavor of fresh vegetables better than any other food preservation method. However, because of rising energy rates, warehousing, transportation and storage, the cost of frozen foods is substantially higher than for canned food or dried food.

The process of preserving foodstuffs in sealed containers, known as "canning," dates back to 1809. Low-acid foodstuffs (as distinguished from acid foodstuffs which can be hot filled) are filled into a metal container, hermetically sealed and thereafter preserved by thermal processing at a time-temperature parameter sufficient to commercially sterilize the contents. The parameters for such low acid foodstuffs range from about six minutes to about seven hours, and from about 212°F to about 275°F, the parameter depending upon various factors such as the type of and initial temperature of the product, the size of the container, the type cf sterilization process used, the operating parameters of the equipment employed, energy costs and the through-put desired.

Prior to development of canning, foods could not be preserved, transported or stored for long periods except in the dry state. Canned foods were the first "convenience" foods. Today's canned foods are not only convenient and nutritious, but are the least expensive compared to other ready-to-serve foods preserved by freezing or any other means.

To successfully preserve most foods, sufficient heat is required to render ^*fche food free of viable microorganisms having public health significance, as well as any other microorganisms of nonhealth significance capable of reproducing in the food under normal storage conditions. The amount of heat and time required to commercially sterilize low

^r _jacid canned foods usually alters and is sometimes damaging to flavor, texture and color compared to the fresh product. Therefore, any treatment that can be made to the food to reduce the time or temperature necessary for sterilization is desirable since it will generally improve quality. Aseptic canning and rotary agitated cookers are examples of equipment which provide high temperature-short time commercial sterilization and, therefore, improve quality. Heretofore, in general, commercial sterilization times and temperatures for low acid foods were from ten minutes to six hours at from about 230°F to 270°F. These times and temperatures are selectable and vary as pointed out above.

The amount of heat necessary to sterilize acid or acidified foods (pH 4.6 or lower) is substantially less than required to sterilize low acid (above pH 4.6) foods. The amount of those acids commonly added to foodstuffs which would be required to acidify foods to pH 4.6 or below, would impart a distinct, sour (vinegary) flavor which would render many products unacceptable.

In spite of all the food preservation processes known to mankind there are some heat-sensitive products, especially certain vegetables, delightful to the taste and quite nutritious in the home-cooked form, which are not available at all as thermally processed products in cans, or as such are available only in a quality which has not obtained general consumer acceptance because of lost texture, degraded color or poor flavor, especially low acid, heat-sensitive vegetables.

In accordance with the invention of copending U.S. patent application Serial No. 778,648, combining a low acid heat- sensitive foodstuff with a mixture of an aldonic acid with its lactones, preferably gluconic acid with its lactones, by the addition to a low acid foodstuff of the aldonic acid or an aldonic acid precursor, preferably one of its lactones, to achieve a pH of 4.6 or lower, enables the low acid, heat- sensitive foodstuff to be commercially sterilized or canned to achieve shelf stability while exhibiting flavor, texture, and/or color closer to the natural or fresh product, very similar to the fresh, home-cooked product, and without the typical pickled sharp, pungent, or acid flavor associated with acids commonly used in foods. Moreover, when a foodstuff is sterilized in a metal container internally coated with a suitable enamel, in accordance with the process of this invention, the result is considerably less internal corrosion and iron pick-up from the metal container than experienced with other acids employed in foods. Additionally, the results are much less impairment of the natural flavor and longer acceptable shelf life.

It has now been discovered that certain acid foodstuffs or low acid foodstuffs having a high natural buffering capacity may be subject to thermal sterilization in the presence of an acid and its lactones whereby one or more of the texture, flavor, or color properties are improved.

An object of this invention is to provide a method for thermally processing acid foodstuffs or low acid foodstuffs having a high natural buffering capacity in the presence of an acid with its lactones, preferably an aldonic acid with its lactones in a container, wherein the presence of the acid improves the flavor and/or color and/or texture of the thermally processed product as compared to that of the same product thermally processed without the acid, and the mildness of the aldonic acid, the level employed, and presence of the one or more lactones with the acid modifies the taste and/or color and/or texture of the thermally processed foodstuff to be significantly improved relative to that obtained with acids such as for example, acetic, citric, lactic, malic, phosphoric and tartaric, commonly employed in foodstuffs.

A related object is to enable any of the foregoing objectives to be accomplished by thermally processing the acid foodstuff or low acid foodstuff in combination with an equilibrium mixture of gluconic acid and its lactones, glucono-delta lactone and glucoho-gamma lactone.

Texture herein generically refers to firmness in relation to touch and bite, and to material consistency and physical integrity. According to the present state of the art, if salt is not used in thermally processing seafood, there is a loss of texture during thermal processing resulting in lack of firmness and resistance to one's bite, which is deemed unacceptable by many people. At present shrimp and other seafoods have to be heavily salted, e.g., in a 4 to 5% brine, to retain their texture during commercial sterilization processing and storage.

From the moment of the death of the seafood item, e.g., shrimp, sardines, or salmon, there is a deterioration in texture due to enzymatic and bacterial action. The result is a breakdown of the connective tissue. Although enzymatic action is largely terminated by the blanching process, blanched shrimp are still extremely heat sensitive, and further loss of texture can occur due to the elevated temperatures involved in thermal processing. Conventionally, a heavy dosage of salt (4 to 5% in the brine) is added to help preserve the texture of the blanched shrimp which would otherwise be degraded during thermal processing.

Some seafoods such as shrimp are presently heavily salted both during the blanch and also in the brine immediately prior to thermal processing (usually 5% by weight sodium chloride in the brine) in order to retain the texture. The consumer ordinarily removes some salt from the shrimp by a water wash or leach before the product is served. Nonetheless, considerable salt is or may be retained in the shrimp in a quantity which many medical authorities consider inimical to health, notably inducement of hypertension due to sodium retention.

Protein foods such as seafood contain sulfur compounds which may break down to react with exposed metal to produce a dark discoloration found in cans of protein-containing foods. Although the dark sulfide compound formed is harmless to consumer health, it detracts from the appearance of the can and when transferred to the product detracts from the appearance of the product.

Scientific studies have shown that the amount of sulfide released from seafood during thermal processing can be related to the acidity of the product. Seafoods, and particularly shell fish, have a tendency toward rapid degradation prior to canning with resultant high pH. Good handling conditions such as prompt icing and rapid processing are very important since they affect pH level amd sulfide formation. Acidification reduces the pH and the consequent likelihood of black iron sulfide formation. Citric acid is frequently added to the canning brine by shrimp canners in an attempt to inhibit sulfide build-up and consequent product discoloration, but treatment with citric acid does not always fully inhibit build-up. This build-aap is most likely to occur at exposed metal at the side seam of a three-piece metal can, at the countersink area, or on the profile rings of the container end.

A further object of the present invention is to produce canned seafood, for example, shrimp, which compares favorably with the fresh or frozen product which is not thermally processed. Another object is to retain the texture of seafood, for example, during thermal processing and storage by a treatment other than heavy salting, by combining an acid and its lactones, preferably an aldonic acid and its lactones, with the shrimp, to be processed with little or no salt added, thereby retaining a flavor closer to that of the fresh product. Yet further objects of the invention are to avoid the need to soak salt from the product before consumption and to improve the flavor by this substantial reduction in salt level. An added advantage is the reduction in discoloration of the seafood and of the metal can in which the seafood may be packed. It is also an object of the present invention to effect the above objectives by thermally processing seafood, for example, shrimp, sardines, or salmon, in the presence of an aldonic acid, preferably gluconic acid, which replaces salt for retaining texture- Still another object of the invention is to provide commercially sterilized shrimp which has a clean shrimp flavor and odor.

Practice of this aspect of the invention eliminates the need for or the use of citric acid in brine to reduce black iron sulfide formation and consequent product discoloration. When an aldonic acid lactone such as glucono-delta lactone is hydrolyzed to gluconic acid, the gluconic acid can perform the same inhibiting action as citric acid. Thus, when GDL is used alone in the brine, neither salt nor citric acid needs to be included since the gluconic acid formed from hydrolysis of the GDL performs these texturing and inhibiting functions. DETAILED DESCRIPTION OF THE INVENTION It has been discovered that by combining a mixture of an aldonic acid and its lactones with acid foodstuffs or low acid foodstuffs having a high natural buffering capability to be thermally processed, the time-temperature parameter required for commercial sterilization of the processed product is considerably reduced so that one or more of the flavor, color, and texture of the foodstuff do not suffer the degradation experienced at the higher parameter needed when the acid is not present. The amount or level of aldonic acid present is that which is sufficient to obtain the improved properties. Preferably such amount will be that amount sufficient to assure that the equilibrium pH of the contents is reduced.

Also an aldonic acid, preferably gluconic acid, has been found to maintain the texture of seafood, e.g., shrimp, making it unnecessary to employ large amounts of salt for this purpose prior to or during commercial sterilization of the product. Only small amounts of gluconic acid are necessary compared to the large amounts of salt previously required. For example, in accordance with a preferred method of combining gluconic acid with Louisiana shrimp, adding 1/2% to less than 1-1/2% (by weight) glucono-delta lactone (GDL) to an aqueous solution is adequate; a level greater than 1-1/2% tends to reduce the appeal. A small amount of salt may still be used in the blanch before sterilizing, but this is far from the amount normally needed to maintain good texture during the conventional canning process in the absence of 4 to 5% salt in the brine. When the present invention is applied to shrimp, preferably the harvested shrimp is first blanched and rinsed, filled into the container, and afterwards GDL (or another aldonic lactone) brine is added to fill container; the container is then hermetically sealed and thermally processed. Because of the addition of an acid with its lactones, e.g., by combining the seafood with aldonic lactones, and the hydrolysis of the aldonic lactones to a mixture of aldonic acids and their lactones, the resulting shrimp has a texture and flavor similar to that of the fresh product when cooked. The levels and mild taste of the aldonic acids and the presence of the acid with its lactones result in a thermally processed seafood that does not have any harsh acidic notes in flavor or aroma. The flavor is also improved by the substantial reduction in salt level. There are a less fishy aroma and less amine formation.

In accordance with this invention, the need for large amounts of added salt or of any added salt at all for maintaining the texture of certain seafoods, for example, shrimp, sardines, or salmon, through thermal processing is eliminated by combining the seafood with a mixture of an aldonic acid and its lactones, preferably gluconic acid and its lactones, and thermally processing the combination. It has been discovered that by combining a mixture of an aldonic acid and its lactones with seafood to be thermally processed, not only are the need for salt for texturizing and the salty taste eliminated or substantially reduced, but also the levels and mild taste of the acid present and the presence of the acid with its lactones, result in a thermally processed seafood that does not have the objectionable pungent, sharp, acidic or pickled flavor notoriously characteristic of those acids used in foods, e.g., acetic, citric, lactic, malic, hydrochloric, phosphoric, or tartaric acid. Moreover, it does not have strong amine-type, fishy aroma associated with fish that are slightly degraded, nor does it have an acid taste.

The aldonic acids which can be combined with the acid or low acid foodstuff or seafood, i.e., the "foodstuff", in accordance with this invention are prepared, for example, by oxidation of sugars or aldoses, preferably from those having six carbon atoms, although they could be prepared from those having five carbon 'atoms. Those acids prepared from sugars having six carbon atoms are talonic, galactonic, idonic, gluonic, mannonic, gluconic, altronic and allonic (although currently these acids with the exception of gluconic may be unavailable commercially) . These acids are respectively derived from their aldoses — talose, galactose, idose, gulose, mannose, glucose, altrose and allose. Sugars having five carbon atoms are lyxose, xylose, arabinose and ribose. Those skilled in the art will understand from this disclosure regarding six and five carbon atom aldonic acids, that other acids which form their own lactone(s) and mixtures of other acids and their lactones, which perform the same functions and objectives of this invention, particularly regarding lowering^, the pH and regarding lack of an objectionable acid taste in the processed foodstuff, would be within the scope of this invention. For example, aldaric acids, i.e., dibasic acids such as glucaric which forms saccharo lactone, might be employed.

Any suitable method or material can be employed to bring the aldonic acid and its lactones into combination with the foodstuff. While the acid might be added by itself (since the acid, when in contact with moisture or water in the foodstuff, will be converted to a mixture of the acid and its lactones) , doing so currently does not appear practical since aldonic acids are not known to Applicants to be commercially available in crystalline form or in food grade. This is the case with the preferred gluconic acid. These acid may be commercially available in technical grade in aqueous solutions. For example, gluconic acid is so available in aqueous solutions stated to be about 50% (by weight) gluconic acid. These aqueous solutions of the acid are equilibrium mixtures of gluconic acid and its lactones, glucono-delta lactone and glucono-gamma lactone.. Gluconic acid has a mild acid taste.

The preferred -method for providing the aldonic acid and its lactones to the foodstuff is to combine the foodstuff with a precursor of the aldonic acid. A precursor of the acid herein means a liquid, material or compound which adds the acid to, or forms or provides it in the foodstuff with which it is combined. Again, when the acid contacts moisture or water in or of the foodstuff, it will convert partially to and will co-exist with its lactones. Precursors of these acid which can be employed include their lactones themselves (which can be said to be latent acids since they hydrolyze in water to form a mixture of the acid and its lactones) , mixtures of these lactones, and salts of the acids in combination with certain strong acids. For example, precursors of the preferred gluconic acid which can be employed include glucono- delta-lactone, glucono-gamma lactone, mixtures of these lactones, and gluconate salts in combination with the strong acid, hydrochloric.

By far, the most preferred precursor for this invention is glucono-delta lactone (GDL) . It is commercially available in food grade as a free-flowing, odorless, white powder. It has a sweet taste. Food grade solutions of GDL are also commercially available and can be employed. GDL is an inner ester of gluconic acid which when hydrolyzed forms gluconic acid. Hydrolysis occurs when GDL is combined with water, for example, that of an (aqueous) brine or in the foodstuff. Hydrolysis of the glucono-delta lactone results in an equilibrium mixture of from about 55% to about 60% (by weight) gluconic acid and from about 45% to about 40% (by weight) of a mixture of glucono-delta lactone and glucono-gamma lactone. The rate of acid formation during hydrolysis is affected by the temperature, the pH value and concentration of the solution. Hydrolysis of delta lactones tends to be more rapid than hydrolysis of gamma lactones. In the absence of heat, hydrolysis tends to be slow. Heating the brine accelerates the hydrolysis reaction and is the preferred method. Heating the foodstuff also has the same effect. Like results would be expected to occur with the use of lactones or other aldonic acids, e.g., galactono-delta lactone. For this invention, rapid hydrolysis through heating is preferred to help acidify the particulate foodstuff rapidly and thoroughly.

Examples of those salts which can be used in combination with certain strong acids (each suitable for food use) , include sodium, potassium and calcium salts, for example, sodium, potassium and calcium gluconates. An example of an acid considered herein to be "strong" is one which will react with the acid salt and provide enough available hydrogen ions to form the desired aldonic acid and its lactones in the foodstuff. Such an acid would be hydrochloric. Of course. the type, manner and/or amount of strong acid(s) employed should be such that in accordance with the objective of this invention, a sharp, strong or objectionable acid taste is not imparted to the foodstuff. If hydrochloric acid is used as . the strong acid, all of it should be converted so that no such acid would remain, only some derived salt.

Practice of the present invention will now be demonstrated by the following illustrative examples using the preferred precursor, GDL, with different foodstuffs. All pH values are at equilibrium. The cans were opened within a week after thermal processing, and at this time the two products, processed differently, were compared.

By equilibrium pH is meant the negative log of the hydrogen ion concentration of the blended product, taken in accordance with CFR 114.80(a) (1) , (2) and CFR 114.90, each incorporated herein by reference, but in any case taken not more than 24 hours after completion of the thermal process, i.e., when the application of heat is terminated.

Salt for flavoring, in identical amounts or equivalent concentration for the size of can and fill weight, need not have been but was added for each vegetable compared. Salting does not feature in the invention. The fill weights were always the same for the two products to be compared.

Example 1 In this example, 303 x 406 cans were filled with 10.5 to 11.0 oz. of whole, peeled tomatoes, topped with juice (160° to 170°F) , and steam-flow closed. The topping juice was prepared in batch quantities and sterilized by elevation of the temperature to 230°F in a heat exchanger.

This run comprised five topping variables and ive cooking time variables. The topping variables were the acidulant additive, namely, (1) 0.50% GDL, (2) 0.75% GDL, (3) 1.0% GDL, (4) 0.3% citric acid, and (5) no acid, and the cooking times were (A) 42 minutes, (B) 35 minutes, (C) 30 minutes, (D) 25 minutes, and (E) 20 minutes. The topping juices were prepared in 20 gallon size batches in a steam jacketed kettle. The pH of the straight tomato juice before any additions averaged 4.4. The topping juices were heated to 160° to 180°F and pumped into the fill bowl. Cans were then filled, topped, and closed under commercial conditions. Initial temperatures averaged 100°F.

Surprisingly, the can center temperatures (CCT) , as measured in two cans per sample, were all above 190oF, even though the processing time was reduced by as much as 50%. The can center temperatures are set forth in the following table:

Table 1 Can Center Temperatures CoF.) Processing Time

Acidulant A B C D E

(1) 201/202 198/196 192/192 192/196 195/182

(2) 204/202 200/201 198/198 196/196 195/198

(3) 200/200 201/201 194/196 192/192 196/192

(4) - 202/204 192/194 194/196 192/190

(5) 202/202 - -

When samples of each were partly analyzed two weeks later after storage in a warehouse, no spoilage was observed.

EXAMPLE 2 After 10 months of storage at 80°F, selected cans from the variables listed in Table 1 were examined for flavor, color, texture 15 and pH level. Since other tests showed enzyme activity at process times of 30 minutes or less, only the 42 minute and 35 minute process samples were examined at the 10 month cutting. Since 0.3% citric acid brine is used commercially in the cannery where the test pack was made, comparison was made between this acid addition and two levels of GDL addition. The results of the evaluation are summarized in Table 2. No significant differences in color or texture were noted. However, the flavor panel included two persons with long experience in the tomato canning industry, and they found a milder, "more natural" flavor with the GDL containing variables, even though the pH readings were as low or lower than with the citric acid "commercial controls." They felt the elimination of the harsh flavor of citric acid represented a distinct improvement in the quality of the tomatoes. TABLE 2

303 x 406 WHOLE TOMATOES

10 mos. storage at 80°F

Juice Acidulant 210°F

Code Level Process Time EH Flavor

1A 0.5% GDL 42 in. 4.1 Mild Acidic

IB 0.5% GDL 35 min. 4.0 Mild Acidic

3A 1.0% GDL 42 min. 3.8 Mild Acidic

3B 1.0% GDL 35 min. 3.9 Mild Acidic

4A 0.3% Citric Acid 42 min. 4.1 Harsh, Acidic

4B 0.3% Citric Acid 35 min. 4.0 Harsh, Acidic Example 3

Frozen blueberries were packed in 300 x 106 2-piece cans in a commercial cannery. The cans were filled with frozen berries, and then heated water or syrup in the temperature range of 160°F-180°F was added. The fill water or syrup additions and the processing conditions are set forth in the following table:

Table 3

% bv Wt. in Syrup

Code GDL Suσar Can Center Te o. _PH

1 2.5 — 180° 3.10

2 2.5 2.5 180° 3.10

3 2.5 2.5* 110° 2.90

4 2.0 — 152° 3.14

5 2.0 2.0 113° 3.15

6 1.0 1.0 113° 3.25

7 — — 180+° 3.43

Control — — 190° 3.45

* 0.3% Calcium Chloride Added.

Because of the use of frozen berries and hand filled syrup, initial temperatures were difficult to control. In addition, the use of small size cans and the fact that the commercial steam tu-nnel was not run at full capacity made accurate control of can center temperature difficult. As a result, some spoilage was encountered due to mold growth, especially in the cans of Code 3, which were then discarded.

One month after packing, sample cans were opened and evaluated for texture, flavor, and color of the blueberries.

The results of this analysis are given in the following table:

Table 4

Code Texture Flavor Color

1 V. si. firm Tart, but acceptable SI. light

2 V. si. firm SI. better than Code 1 SI. light

3* —

4 SI. firm SI. tart, acceptable SI. light

5 Firm SI. tart, better than

Code 3 SI. light

6 Firm SI. loss of flavor SI. light

7 Soft Normal, v. si. tart SI. dark

Control Soft Normal, v. si. tart SI. dark

* Discarded due to mold growth

It was judged that Code 5 presented the best combination of improvements, particularly in texture, and it was desired to determine whether these improvements would carry over to the baking of blueberry muffins, the use for which this size can is intended. Accordingly, a comparison was made between Code 5 berries and control berries using the commercial muffin mix product that accompanies the commercial cans. In mixing, it was noticed there was less bleeding of the blue color into the dough with Code 5 berries. When the muffins were packed, this resulted in a clearer yellow color to the Code 5 muffins, and the exterior surface appeared pinkish brown as contrasted to the slightly greenish brown color of the control muffins. Blind tasting occurred with five tasters, and they unanimously preferred the flavor of the Code 5 muffins over the control muffins. Examτle 4 Frozen whole kernel corn was processed without acidification in a still retort for 26 minutes at 250°F in 300 x 407 cans. The yellow corn had a slight greyish tinge, the texture was slightly soft, and there was a slight caramelized note to the flavor. In other words, this product was cooked longer than desirable to get its optimum characteristics. An improvement in color was obtained by the addition of 0.5% GDL to the brine, but the thermal process remained the same and the flavor was good. Frozen whole kernel corn was acidified with a brine containing 1.0% GDL. The pH was reduced to 5.3, and the processing time was reduced to 18 minutes. The greyish color tinge was eliminated and the corn was bright yellow, the texture was firm and close to that when fresh corn is home cooked, and the flavor had a slight acidic note. Frozen whole kernel corn was acidified with a brine containing 1.5% GDL, and the pH was reduced to 4.8. The processing time was further reduced to 11 minutes. The flavor was acidic with raw and corn cob notes. A brine containing 2.5% GDL was required to reduce the pH below 4.5., i.e., 4.4. The thermal process was 9 minutes at 225°F, and the flavor was very acidic with raw and corn cob notes.

The processing conditions and the results are set forth in the following table:

TABLE 1 Corn Processed to Commercial Sterility in 300 x 407 Cans

Sample :

Acid added to Brine (% by weight) 0 0.5 1.0 1.5 2.5 3 > Equilibrium pH 6.8 6.1 5.3 4.8 4.4

_)

Processing Time (Min.) ) 2266 26 18 11 9 I --

Processing Temp (°7) 2 25500 250 250 250 225

Color SI. grey - Lt. Bright Bright Bright Dark Yellow Yellow Yellow Yellow Yellow

Texture SI. firm SI. firm Firm Firm Firm Flavor SI. Best SI. Acidic V. Acidic Carmelized Acidic raw corn raw corn cob cob

Example 1 and Table 1 show that the addition of 0.5% GDL to the corn obtained improved color and good flavor. It would be reasonable to expect that for the corn used for this test, an acceptable range of GDL would be from about 0.4% to about. 0.7% in the brine. It should be noted that an improvement in color by use of the mixture or precursor thereof of this invention can be obtained without a reduction in thermal processing temperature below that which be used without an acidulant.

Example 5 If cut green beans are processed without acidification for 13 minutes at 250°F, but green beans would have a drab green color, the texture would be soft, and the flavor would have an overcooked note. In other words, this product would have been cooked longer than desirable to get its optimum characteristics. If the green beans are acidified with a brine containing 0.4% GDL, the pH would be reduced to 4.8, the processing time to 8 minutes, and the quality would be improved. The texture would be firm and close to that achieved when fresh green beans are home cooked, and the flavor would be good with slight or no acidic notes. If the amount of acid were increased to 0.8% in the brine, the pH would be 4.3, and the process would be further reduced to 4 minutes at 250°F. This process is less than what is used for home cooking fresh green beans, and the texture would be very firm and crunchy. The flavor would have a slight acidic note, and, therefore, the 0.4% GDL brine would be preferred.

Expected process parameters and results are set forth in the following table: Table 6 Green Beans Processed to Commercial Sterility in 303 x 406 cans

% GDL Added to Brine: 0 0.4 0.8 Equilibrium pH 5.2 4.8 4 3 Processing Time (Min.) 13 8 4 Process Temp. (°F) 250 250 250 Color Drab green Drab green Drab green

Texture Soft, mushy Firm Firm, crunchy

Flavor Overcooked Best SI. acidic

Example 6 Louisiana shrimp, freshly caught, were mechanically peeled and deveined. The shrimp were of medium size, which means 5.4 to 9.7 per ounce of drained product. The pH of the raw shrimp to be processed ranged from 7.1 to 7.3. The shrimp were blanched for 1-1/2 minutes at 200oF in a continuous blancher. The blanch solution was an aqueous solution containing 3.95% salt by weight and heated to 200°F. The shrimp were rinsed after the blanch to cool the shrimp, and they were graded and immediately filled into cans (307 x 113; meaning 3-7/16 inches diameter, 1-13/16 inches high) . The rinse removed some of the salt. Each can was check-weighed to assure a fill weight of 4.3 oz. After filling, the commercial control cans (CC, Table 7) were passed through a conventional drip line whereby the cans were filled with a brine solution which contained 4.8-5.0% salt by weight.

In accordance with the present invention the commercial brine solution was replaced with brine solutions to which had been added various amounts of GDL and 1.3% by weight salt dissolved in water. These brines were heated to 180-190°F and employed as the canning brine for a series of other 307 x 113 cans (refer to Table 7, below). The GDL in the brines undergoes hydrolysis and thereby provides in the brine a solution in which from about 55% to 60% by weight of the GDL added is in the form of gluconic acid and from about 45% to 40% by weight of the GDL added is in the form of a mixture of glucono-delta lactone and glucono-gamma lactone.

All cans were steam-flow closed and were thermally processed in vertical still retorts. The thermal process used for the control cans and those of the present invention was a retort temperature of 261oF for 5.43 minutes. The cans were atmospherically water-cooled to about 100°F after processing, and both sets of cans were stored at a controlled temperature of 80°F. The objective was to monitor the differences between the various cans to which GDL had been added and the commercial control cans in terms of the sensory characteristics of odor, color, flavor, and texture, based upon the GDL variable.

Two cans of each of the following code variables shown in Table 7 were submitted to a trained taste panel whose evaluations are given in Table 8.

TABLE 7 GDL added % Salt Added

Code Variables to the brine to the brine

B 0 1.3*

C 0.5 1.3*

D 1.0 1.3*

F 1.5 1.3*

CC (Commercial

Control) 0

*Amount added to avoid a bland taste.

TABLE 8

Sample Code Aroma Flavor Texture Color

B Some fishy note Somewhat Soft or Slight fishy mushy gray pink

C Very slight loss Cleaner Slightly Bright of fishy note shrimp note firm pink-red than the control

Three panel members reported an off-note described as slightly harsh, pungent or (amine) like

Best aromatics of Better than Firm Bright all samples. control pink-red Fishy note because of decreased clean shrimp and shrimp note flavor with most evident; slightly sweet another comment flavor was it had clean aroma

Slight loss of Downgraded Flaky dry; Slightly aromatics because: firmest, less slightly acid too firm pink- flavor, lower red shrimp flavor

CC Shrimp house Extremely Firm Bright or fishy salty, some¬ pink-red what fishy

It was also noted by the panel that the cloudiness of the liquid (brine) in the can was obvious at the 1.5% GDL addition level but barely noticeable at the 0.5% level. These liquids are termed ^brine* in the canning industry regardless of salt content. Because of brine cloudiness at the 1.5% GDL level and the downgraded flavor, the preferred range of addition of GDL to brine for use with small and medium Louisiana shrimp under the present invention is from about 0.5 to less than 1.5 percent by weight in water. Conceivably some GD (a fraction of a percent) may be replaced by a small amount of an organic acidulant, such as citric or lactic acid, to still achieve equivalent results in accordance with this invention, and a small amount of salt (NaCl) may be used to boost or encourage the seafood flavor. Citric acid is not known to have ever been used to replace salt for texturing but has been used to prevent sulfide deposits.

Example 7 Four frozen Pacific pink salmon (deheaded and eviscerated) were thawed. Each salmon was skinned, deboned, and cut into pieces of appropriate size.

The containers used were 2-piece 307 x 112 (meaning 3- 7/16 inches diameter, 1-12/16 inches high) enameled cans. Six ounces of thawed fish w re weighed into each can containing 0.06 oz. salt (1.0% by weight of fish). The fish of Sample 6 was dipped for 30 seconds in a solution containing 20% GDL before it was filled into cans.

Sample 1 was filled with deionized water and Sample 2 with soybean oil. n accordance with the present invention, the commercial brine solution was replaced in Samples 3 to 5 with brine solutions to which had been added various amounts of GDL. Table 1 describes the levels of GDL used and the resulting pH of the fish. All of the brines were heated to 180-190°F.

All cans were topped to an aim headspace of 1/4" and were closed under .25" vacuum. The thermal process used -for all cans was a retort temperature of 248°F for 65 minutes followed by an atmospheric water cool to about 100°F. The cans were processed in a vertical still retort.

The make-up of the brine solutions employed and the pH of the salmon are set forth in the following table:

TABLE 9

% GDL Added pH of Salmon 24

Sample Brine Solution* to the Brine** hours after processing 1 Deionized Water 0 6.4

2 Soybean Oil 0

3 Soybean Oil 0.8 5.7

4 Deionized Water 0.8 5.8 5 Deionized Water 0.4 6.0 6 Deionized Water 20.0% Dip 5.7

* Each brine contained 1% salt by weight of the salmon. **Based upon the weight of the fish.

The differences between the various cans to which GDL had been added and the control cans in terms of the sensory characteristics of appearance, aroma, texture, and color were informally evaluated. These are summarized in the following table:

TABLE 10

Sample Appearance Aroma Texture Color

1 White Coagulation Cooked Softest White

2 White Coagulation Soft White

3 Slight Coagulation Firm Light Pink

4 No Coagulation Best Firm Pink 5 No Coagulation Slightly Firm Light Pink

No Coagulation Acidic Dry Darkest Pink It was noted that GDL, even at low levels, presents the formation of curd (coagulated soluble proteins) on the fish surface. Curd is typical in salmon which are frozen before canning but can also form in fish packed fresh. Curd formation lowers both grade and economic value of the product.

The firmness of the salmon is related to the amount of GDL used in the brine. The more GDL in the brine, the firmer the processed salmon was after process. Salmon was most liked when the brine contained GDL at the 0.8% level. The texture was firm and also the taste was preferred among all the variables.

The variables with GDL also had more typical pink salmon color than the controls. The dipped salmon had the most intense pink color.

The preferred range of addition of GDL to brine for use with Pacific pink salmon under the present example is about 0.8% by weight in water. If one preferred adding GDL to the product by dipping into a GDL solution, much higher concentrations of GDL in solution would be required.

Overall, Sample 4 had the best characteristics and was superior to the control variable. This sample had the best odor characteris-tics and was a desirable, pink color.

EXAMPLE 8 Ten 1/4-lb. rectangular (405 x 301 x 014.5) cans of each sample were prepared by adding 20 ml of brine acid solution to the empty cans and then transferring freshly trimmed, raw sardines from other cans into the test cans. The test cans were placed in racks which were placed in the bottom of a cart containing 40 racks of cans to avoid any possible contamination of regular fish through overflow of liquid in the steam box. The cart was wheeled into the steam box where it was treated with live steam at atmospheric pressure for 35 minutes. The test racks were removed while st._ll in the upright position so that the pH of the brine and fish in each sample could be checked.

On can of each sample was checked after cooling to room temperature. The pH of the decanted brine was checked, and then the drained fish was blended with 60 ml of distilled water added to make a satisfactory blended slurry. The results of the pH evaluation shown in Table 11 indicate that acifidication during steaming was ineffective. Thus, additional acid was added to Samples 2 and 3 prior to closing.

TABLE 11 pH Check after Steaming Sample Brine Fish + Water

1 6.17 6.25

2 4.68 6.25

3 6.17 6.25

The amount of the acid, i.e., GDL or citric acid, added per can to Samples 2 and 3 both before and after steaming are set forth in Table 12, based on an average drained weight of fish of 120 gm per can:

TABLE 12

G GDDLL AAddddeedd BBeeffoorree GGDDLI Added Before Citric Acid Added

Steaming Closing Before

Closing

Sample % Wt. of Fish % Wt. of Fish % Wt. of

Fish

1 0 0

2 0.67 0.33

3 0 0.830 0.167 The test cans were drained manually and put into the line for addition of oil and closing. The nine remaining cans of Sample 2 had 2.0 ml of 20% GDL concentrate solution added prior to filling with oil. Sample 3 cans had 5 ml of 20% GDL concentrate containing 4% citric acid added prior to filling with oil. Cans were then retorted for 74 minutes at 238°F, which is the normal cook. The test cans were placed in bags to separate them from the other cans in the retort. After cooling, one can of each of Samples 1, 2, and 3 was checked for pH of the brine, the fish drained and blended with distilled water, pH checked, and the fish and brine recombined. Addition of 60 ml of distilled water was necessary to obtain a satisfactory blended fish paste. The results of this check are given in the following table:

TABLE 13

Brine Fish & Water Fish & Brine

Sample E2 EH (blended pH

1 6.36 6.45 6.43

2 5.44 6.24 6.18

3 3.46 5.87 5.72

The results in Table 13 show that the brine in Sample 3 is well below a pH of 4.6, but the fish, while reduced slightly in pH, were still well above 4.6 pH.

Cans from each of Samples 1, 2, and 3 were evaluated by three regular fish graders of the Maine Sardine Council as well as an officer of the Council. Their comments were as follows: TABLE 14 Sample Tasters' Comments

1 Good, slightly low in salt, slightly soft

2 Clean odor, less fishy, texture slightly firmer, no acid flavor

3 More of a difference, definitely low in salt, slight burning in back of mouth

Those skilled in the art of thermally processing foodstuffs whose heating characteristics have been established can determine by known calculations (available in the aforementioned publication) a sterilizing value (CCT) which will achieve commercial sterilization for the product in question and the type of retort or process to be employed. For products which heretofore never have been commer-cially sterilized and canned or for which no heating characteristics have been developed, it is recommended that an established thermal processing authority such as the assignee of this invention be consulted to obtain a sterilizing value (CCT) which will achieve commercial sterilization for the equilibrium pH of the particular product contents to be processed. For all products whose equilibrium pH has been lowered to 4.6 or below, a CCT of 205°F can be employed for commercial sterility. Should it be desired to use a CCT of less than 205°F, an aforementioned authority should be consulted to determine whether the lower CCT temperature would be sufficient to obtain commercial sterility.

The can or container center temperature (CCT) is determined by implanting a thermocouple into the container prior to its being hermetically sealed and tested. CCT herein means the temperature at the slowest heating point of the food product in the container which, depending on the food product, may be but is not necessarily the actual center point of the container.

Another advantage of this invention is that it increases the practicality of using still retorts for thermal sterilization to produce good quality canned food on a commercial basis, since still retorts require longer times at equivalent temperatures to reach an equivalent sterilizing value compared to continuous agitating retorts.

Since GDL is available in the form of a white, crystalline powder, it can be added as such directly to a foodstuff prior to thermal processing. This would apply for example to those foodstuffs wherein the addition of water or brine is undesirable. Hydrolysis of the GDL to gluconic acid and glucono-delta lactone and glucono-gamma lactone would not be as rapid as it would be if water or a previously prepared brine were added.

As previously mentioned, this invention is applicable to acid foodstuffs such as tomatoes, fruits, and berries, which are heat sensitive in the sense. More particularly, this invention is directed to tomatoes and blueberries. One skilled in the art would appreciate that other specitic fruits and berries are encompassed hereby.

The GDL employed in the samples of this invention was in the purity grade complying with FAO/WHO standards and USA Food Chemistry Code. FAO designates the Food and Agriculture Organization of the United Nations; WHO designates the World Health Organization. The chemical may be acquired from Pfizer Chemical Co. or Finnsugar, Helsinki, Finland. In some instances, as in the above examples, it may be desirable for taste to add a small amount of salt, sugar or other seasoning, or to modify GDL with a small quantity of an acidulant such as citric acid to increase the buffering capability of the GDL to assure stabilization of the pH of the contents at the desired level. The acidulant added may permit a slight departure from the preferred quantities of GDL set forth above for these products but so long as the pH is reduced, and the processing parameter is favorably displaced, with substantially the same results as given above, i.e., without a objectionable acid taste, such modifications amount to the practice of the present invention or the equivalent.

Since the present invention makes possible reduced are retained instead of being lost into the brine during processing and storage.

Steam retorting (either stationary batch, or continuous agitating) is the preferred means of thermal processing low acid foods in accordance with this invention although any suitable means may be employed. For processing low-acid foods, such as corn, peas, and green beans, the preferred temperature range is from about 212°F to about 270°F for foods such as corn or peas and from about 212°F to about 255°F for green beans.

The present invention may be employed with respect to any thermal processing technique including gas flame sterilization and asceptic processing. In gas flame sterilization, a foodstuff in a sealed container is sterilized by agitating the container, e.g., by rolling it, as it passes over a gas flame. In aseptic processing and packaging, a commercially sterilized product is filled into a presterilized container and then aseptically and hermetically sealed with a presterilized closure in an atmosphere free of microorgan-isms. Employing an aldonic acid/lactone mixture such as by combining GDL with the foodstuff to be aseptically processed and packaged should reduce the aseptic process time-temperature parameters needed to achieve commercial sterility.

Although metal cans were employed in the examples, the invention is not dependent on this type of container or the material of which it is made. The invention and its advantanges can be achieved using suitable rigid plastic containers, single or multiple layer, and it will be readily apparent to those skilled in the art that the invention is also applicable with glass containers, suitable semi-rigid containers and flexible containers such as pouches, with or without foil. This is discussed more fully below.

Conventionally, thermal processing of foodstuffs in metal containers is carried out at temperatures ranging from about 190°F to about 280°F for from about several minutes to over six hours in various equipment such as rotary continuous subjected to one of these cook cool cycles before they are discharged, stacked and packed for shipment and distribution. The highest processing temperatures are usually applied to low acid foods which provide a better media for growth of microorganisms than do acid foods. Acid foods require less heat because some microorganisms are quite sensitive to acids. The preserving effect of acids is due to their hydrogen ion concentration and destabilization effect on bacterial cells. Acids may be found in foods as a natural component, produced in foods by fermentation, or added to foods directly as a chemical. Since acid enhances the lethality of heat, acid foods (pH 4.6 or below) need only be heated generally up to about 205°F, which is much lower than the heat needed for foods of higher pH to render them free of spoilage organisms. Thus, there are certain foods, particularly low-acid vegetables (some of which are hereinafter enumerated) which require thermal processing at a relatively high temperature for a long period of time (high time-temperature processing parameter) in order to kill microorganisms responsible for food spoilage and toxicity.

Much effort has been expended to packaging foods in plastic containers as a substitute for metal and glass containers. Plastic containers are desirable because they provide advantages of low cost, light weight, lack of rust and corrosion problems, and ease o disposability. However, whereas metal and glass containers commonly used for packaging and preserving foodstuffs have no difficulty in withstanding thermal processing temperatures which are higher than about 190°F and importantly they can easily withstand the highest thermal processing or retorting temperatures used commercially (currently around 275°F to 280°F) without permanent distortion or loss of their hermetic seal. Rigid plastic containers, for example, those made of olefinic structural material such as polyethylene, polypropylene or blends thereof, soften increasingly as the elevated thermal processing temperature increases and as the materials approach their respective melting point is about 275°F, and for a homopolymer of polypropylene ii is about 330°F. While softened, the plastic distends and tends to distort due to relative internal/- external pressures and handling. In conventional thermal processing of plastic containers, unless various thermal processing factors are very closely controlled, the container, upon cooling, will be permanently distorted and therefore have an unacceptable configuration. One reason that the softened plastic at the elevated thermal processing temperature distorts is that the pressure within the container during thermal processing exceeds the external pressure, i.e., the pressure in the equipment in which the process is carried out. The internal pressure against the plastic wall causes the wall to distend outwardly. Factors which contribute to increasing the internal pressure within the container are that the small amount of air or other gases usually present in the hermetically sealed container head space (above the food level in the container) undergo significant increases in volume and pressure at the elevated temperatures. Additionally, internal pressures also develop due to thermal expansion of the product, increased vapor pressures of the products, the dissolved gases present within the foodstuff contents and the gases generated by chemical reactions in the product during its cooking cycle. Thus, the total internal pressure within the container during thermal processing is the sum total of all of the aforementioned pressures. When this pressure exceeds the external pressure, the container distorts outwardly, thereby tending to expand the gases in the head space and thereby reducing the pressure differential relative to the external pressure. Usually, attempts are made to assure that the external pressure always exceeds the internal pressure such as by processing the filled container in a water medium with an over-pressure of air sufficient to compensate for the internal pressure. This is one of the means used to process foods packed in well-known flexible film packages such as the retort pouch. Also, external pressure in a steam

SUBSTITUTE SHEET this reduces heating efficiency of the steam and can alter heat transfer within the retort. When the container is cooled, pressure within the container decreases relative to the external pressure and consequently the side wall and/or the bottom wall of the plastic container distends inwardly to compensate far the: reduction in pressure. Cooling also tends to rigidity the plastic. This can cause the container to be permanentl distended outwardly and/or inwardly.

It is- well, reασβpiized that major problems in developing rigid, thermally prσcessable plasticcontainers and in developing:^*methods for thermally processing foodstuffs in such containers- have been distortion and leakage of the plastic containers during processing and the complexity and criticality involved in controlling the-filling of the containers, the amount of headspace, relative internal and external pressures, cooling rates, handling and other factors which affect distortion and strength of the container walls and whether or not the distorted walls become permanently deformed in unacceptable configurations. Such deformations can be side wall bulging, side wall panelling (buckling of the side wall inwardly) , and/or outward distortion of the container bottom wall referred to as "bulging" or "rocker bottom". These deformations and distortions may be unsightly, may interfere with proper stacking of the containers during shipment, and may cause them to rock and be unstable when placed on flat surfaces. Any such deformation may be perceived as a possible indication of spoilage of the food contents, thus resulting in rejection of the container by the consumer. Unless these distortions and deformities and related problems are eliminated or substantially reduced it will be difficult to develop and provide low-cost, universally satisfactory commercially thermally processable rigid plastic containers for foodstuffs as viable commercial alternatives to thermally processable metal and glass containers.

A problem associated with controlling the headspace within a narrow range to limit or control internal gas and foodstuff filling equipment does not always fill the container with precisely the same amount of food, all plastic containers are not always exactly of the same dimensions and capacity, and there may be spillage. Because or these factors, the headspace above a foodstuff in a plastic container can vary during a run, and can be difficult to control within a narrow range. The narrowness and criticality of allowable headspace range has been a particular problem which has contributed to the overall complexity of the thermal processing of plastic containers, and has made commercial thermal processing of plastic container difficult.

A problem associated with the high temperatures of conventional thermal processing is that at the higher retorting temperatures the plastic is softer and weaker, and the plastic is more easily stressed. One result is that the container at those temperatures tends not to have sufficient crush resistance to withstand many containers being stacked thereon during still retorting. For example in a test simulating 14 layers of cans, the bottom-most layer was evaluated. The cans were subjected to a still cook at 250°F for 65 minutes. All 16 cans of the bottom layer were severely crushed and were deemed to be unacceptable for commercial use. In a second test at 245°F for 75 minutes, all cans exhibited slight crushing. In a third test, at 240°F for 90 minutes, all 16 cans were examined and none exhibited crushing. Thus, the lower the still retort temperature, the greater the crush resistance of the containers on the bottom row and the greater is their ability to withstand the weight of containers stacked over them. Another result is that those containers whose walls are not manufactured to have good uniform material distribution or have thin or weak spots, will, due to the internal pressures, be first and/or excessively stressed and distended in those areas, relative to other more uniformly thick areas. Thus, plastic containers intended for thermally processing foods at the higher temperatures require a greater degree of.uniformity in material distribution than containers intended to be processed at the lower temperatures.

TESHEET Still another problem involved in thermal processing of plastic containers, rigid or flexible, is that the hermetic seals may rupture. At high enough temperatures, if the previously rigid bDdy hook softens enough, it may unfold from the double seam and cause the metal end to blow off. Hermetic seals formed by use of heat sealing adhesives made of lower melting polymers, may also rupture under the influence of internal and external forces developed at the elevated thermal processing temperatures, e.g., above 240°F.

Although it is recognized that it may be possible to make plastic containers from highly rigid resins with sufficient thickness in the side and bottom walls, and/or to use higher melting polymers and adhesives to better withstand the temperatures and pressures developed during thermal processing, practical considerations such as costs associated with the greater amounts of these resins, the increased weight, the decreased thermal conductivity, increased plastic container manufacturing time (heating, cooling, etc.), and other factors militate against use of this approach.

Another approach to thermally processing foodstuffs in plastic containers is to maintain the thermal processing temperature at a level low enough that the polymers do not soften significantly. However, this approach requires significantly longer processing times to achieve the same level of commercial sterility of the foodstuff. The extended times produce no relative energy cost savings, increased time reduces throughput in the equipment and often, particularly with respect to low acid foodstuffs, they will result in the foodstuff being of poorer quality in terms of its texture, ^" color, and flavor. The extended thermal process tends to overcook the foodstuff compared to the quality of the same foodstuffs processed at higher temperatures for shorter times.

In view of the aforementioned problems, it would be desirable and it is an object of this invention to provide methods of thermally processing foodstuffs in plastic containers, both rigid and flexible, which would overcome or -substantially reduce these problems.

Accordingly, it is an object of this invention to facilitate the thermal processing of plastic food containers packed with foodstuff and to provide thermally processed plastic containers which have an acceptable configuration. It is another object of this invention to reduce the temperature needed to thermally process foodstuffs in plastic containers to thereby alleviate the problems associated with softening of plastic at the more elevated thermal processing temperatures and the problems of plastic container wall distortion and of the permanently deformed configurations associated therewith.

Yet another object of this invention is to reduce the thermal processing time/temperature parameters, especially the temperature, as well as the energy utilized and to maintain throughput in thermal processing of plastic containers packed with foodstuffs.

Still another object of this invention is to take advantage of the possible lower thermal processing temperatures and parameters to enable the use of thinner plastic containers, and to permit the foodstuff thermally processed in the plastic container to have at least the same quality as that provided in a metal or glass container along with the advantages attendant in having containers made of plastic rather than metal or glass.

Still another object of this invention is to achieve the aforementioned objective of facilitating the thermal processing of foodstuffs in plastic containers by increasing the headspace range with respect to which and within which a foodstuff can be successfully and easily filled and thermally processed in a plastic container.

Another object is to make the thermal process and the reformation of distorted plastic container walls less complicated and less critical.

Yet another object is to provide better plastic container performance and strength during thermal processing by effecting the process at lower temperatures, and to provide

UBSTITUTESHEET resulting thermally processed plastic containers of food having commercially acceptable aesthetic, physical and performance characteristics.

It is a specific object of this invention to provide a method of thermally processing foodstuffs in plastic containers at lower temperatures than without an acidulant, whereby the acidulated foodstuff has one or more improved organoleptic qualities, such that the total organoleptic effect is as pleasing or more pleasing than it would be if the same product were processed at higher parameters without an acidulant.

It is another object of this invention to provide the aforementioned objectives wherein the acidulant used is a mixture of an acid and its lactones wherein the acid may lower the pH, for example, to 4.6 or below, and the amount and type of acid employed and the presence of the acid with its lactones does not impart an objectionable acid taste such as the strong, sharp, pungent, sour, or "pickled" flavor associated with acids commonly used in foods.

This invention solves the aforementioned problems and meets the above-mentioned objectives. This invention provides the advantages over conventional thermal processing of plastic containers in that the lower thermal processing temperatures permitted by this invention create less internal gas build-up and less internal pressure against the container walls. Therefore, there is less stress and distention of the plastic walls and less chance of the container bursting, rupturing, leaking or permanently distending beyond the container material's elastic limit. Further, the lower temperatures greatly facilitate the thermal process and make it much easier to reform the container walls to an acceptable configuration The allowable headspace range is broader and less critical, and the control of the relative internal/external pressures is less critical, there being less need, if any, for over pressure cooling. In terms of container performance during processing at the lower temperatures wherein the plastic is not as soft, the plastic, and the container are stronger and can resist more stress. Thus, at the lower processing temperatures in a still retort, containers exhibit better resistance to crushing and more containers can be placed on top of one another, thereby increasing the retort output. Also, container wall uniform material distribution is not as critical. In terms of economy, the thermal processing apparatus can be simpler in that overpressure cooling apparatus may not be needed. Retorts not already equipped for overpressure cooling can now be utilized. Since the thermal processing and cooling times can be reduced, and since, for example, more containers can be still retorted due to increased stacking, there can be economies through the increased thermal processing output. Economies can also be obtained by using thinner wall constructions or less expensive, weaker structural materials.

With respect to improvements in terms of the foodstuffs processable in plastic containers, since less gas is evolved at the lower temperatures, it is easier to thermally process products which tend to evolve greater amounts of gas such as corn, dried beans, and dried bean products such as chile with beans which heretofore were more problematical in plastic containers at the higher temperatures. The lower thermal processing parameters of this invention permit the thermal processing in plastic containers of heat-sensitive food¬ stuffs such as low acid heat-sensitive vegetables which, due to the higher conventional thermal processing temperatures and/or longer times, tend to degrade in organoleptic qualities (texture, i.e., firmness and compositional integrity, color, flavor, and aroma) . Under the process of this invention these vegetables are less overcooked, are not flaccid and are more firm, the color tends to be brighter, and the flavor improved, all relative to the same products processed at the higher temperatures for the same length of time or longer. Also, foodstuffs processed in plastic containers at the lower temperatures have organoleptic properties closer to the fresh or properly home-cooked product than the same products thermally processed at the higher time/temperature parameters. When the preferred acidulants are employed, masking of the fresh natural flavor of the foodstuff by an objectionable acid taste is minimized or eliminated.

Reducing the temperature to which plastic containers are subjected during thermal processing to low enough levels might permit the use of other thermoplastics which as structural materials, would soften and melt at lower temperatures than the blends used in Example 9. Such a material when employed with an oxygen barrier layer (such as an ethylene vinyl alcohol copolymer, vinylidene chloride copolymer, nylon or other layer which is a better oxygen barrier than the structural layers) may advantageously provide a potential for less expensive rigid plastic packages for thermally sterilized food products than currently available.

An advantage of this invention is that methods are provided for thermal processing acid foods such as tomatoes, fruits, and berries such that these foodstuffs can be thermally processed at even lower temperatures than usually employed even without an acidulant such that these foodstuffs have one or more organoleptic properties closer to that of the natural fresh cooked product and improved over what would be if an acidulant other than the mixture or the precursor thereof were employed. Another advantage of the method of this invention with respect to acid foodstuffs is that lower thermal processing parameters, especially lower temperatures, permit the use of lower melting plastic materials.

Reducing the thermal processing temperatures for multi¬ layer plastic containers having an inner moisture-sensitive oxygen barrier Mayer, such as an ethylene vinyl alcohol copolymer material, would reduce or eliminate the need for a drying agent to be incorporated into a layer of the structure to protect the barrier from moisture (see U.S. Patent No. 4,407,897), since depending on the level of the lower processing temperature, there will be less or little permeation of moisture through the outer structural polyethylene or polypropylene layers to the barrier layer during retorting. With less or little permeation there is less of a need for a drying agent to absorb the permeated moisture.

The foregoing and other objects, features, and advantages of this invention will be further appreciated from the following detailed description and accompanying drawings.

In accordance with this invention, a method is provided for thermally processing plastic containers with foodstuff therein, at lower temperatures than heretofore conventionally practiced. More particularly, a method is provided for substantially reducing side and bottom wall distortion of a plastic container during thermal processing of a foodstuff hermetically sealed therein, which comprises combining the foodstuff with an acidulant in an amount sufficient to reduce the time/temperature requirements for commercial sterilization and/or to reduce the equilibrium pH of the foodstuff and contents, and thermally processing the foodstuff in the plastic container at a time/temperature parameter sufficient to achieve commercial sterilization of the foodstuff yet substantially lower than otherwise possible from a commercial sterility standpoint if said acidulant were not added and/or if said equilibrium pH were higher during thermal processing. The lower time/temperature parameter substantially reduces the side and bottom wall distortion of the container during thermal processing, greatly facilitates the thermal process and cooling process and the control of their parameters and results in a thermally processed plastic container having an acceptable configuration.

Although the invention applies with respect to any foodstuff and any acidulant appropriate for reducing the time/temperature parameter for commercial sterilization and/or for reducing the equilibrium pH as aforesaid without significantly deleteriously affecting the flavor of the foodstuff, the invention is especially applicable to low acid foodstuffs that normally require high processing temperatures to render them shelf stable and especially those low acid foodstuffs which are heat-sensitive in the sense that they are susceptible to degradation in texture, color, or flavor due to

SUBSTITUTESHEET the more severe conventional thermal processing parameters and conditions. The preferred acidulant is a mixture of an acid and its lactones, preferably an aldonic acid and its lactones, e.g., a mixture of gluconic acid and glucono-delta lactone and glucono-gamma lactone, preferably provided to the foodstuff by combining the foodstuff with glucono-delta lactone (GDL) (which hydrolyzes and forms a mixture of gluconic acid and its aforementioned lactones) because it is effective in reducing the time/temperature parameter required for commercial sterilization and/or in reducing the equilibrium pH of low acid foodstuffs without imparting a strong, sharp, pungent, pickled or acidic taste more commonly associated with other acidulants such as acetic, citric, lactic, malic, tartaric, and phosphoric acids which are commonly used in foods.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, wherein like numerals are employed to designate like parts:

Figure 1A is a front elevational view partly in section, of an open-ended cylindrical plastic container of this invention before the container is packed with food and sealed;

Figure IB is a front elevational view partly in section, of the container shown in Figure 1A after the container has been filled with food and sealed under partial vacuum;

Figure IC is a front elevational view partly in section, of the container shown in Figure IB during' thermal processing but before reforming, showing bulging of the container bottom wall;

Figure ID is a front elevational view partly in section, of the container shown in Figure IC illustrating rocker bottom after thermal processing;

Figure IE is a front elevational view partly in section, of a container similar to Figure ID but wherein the container sidewalls are panelled;

Figure IF is a cross sectional view taken along line IF - IF through the container shown in Figure IE;

Figur _. 1G is a front elevational view partly in section. of the container shown in Figure 1A illustrating sidewall panelling and bottom bulging;

Figure 1H is a front elevational view partly in section, of the container shown in Figure 1A after thermal processing, according to the present invention and having a commercially acceptable configuration.

Figures 2 through 7 each show representative parameter curves for thermally processing a different low acid foodstuff to commercial sterility, the curves to the right illustrating conventional parameters needed without an acidulant, the curves to the left illustrating parameters needed by using an acidulant, i.e., the preferred GDL, in combination with a foodstuff in accordance with this invention. Figure 2 being for yellow squash. Figure 3 carrots, Figure 4 green beans, Figure 5 green peas. Figure 6 corn, and Figure 7 lasagna.

In accordance with this invention, the foodstuff to be thermally processed in the plastic container is combined with an acidulant, the amount of the acidulant being sufficient to reduce the time/temperature parameter required for commercial sterilization and/or to reduce the equilibrium pH of the foodstuff contents in the plastic container prior to thermal processing. By equilibrium pH is meant the negative log of the hydrogen ion concentration of the blended product, taken in accordance with CFR 114.80(a) (1) , (2) and CFR 114.90, each incorporated herein by reference, but in any case taken not more than 24 hours after completion of the thermal process i.e., when the application of heat is terminated.

The foodstuffs which can be thermally processed in plastic containers in accordance with this invention can be any foodstuff, regardless of the level of its acidity, i.e., acid, acidified, or low acid. Thus, the invention is applicable to any acid foodstuff naturally or otherwise already having a pH 4.6 or below, the acidulant being added to increase the acidity even further to thereby enable the thermal process to be conducted at a still lower time/temperature parameter which has even less an effect on the plastic of the container. The invention is, however, also

S - T1TUTE SHEET _directed to low acid foodstuffs having a pH above 4.6, regardless of whether the foodstuff is particularly sensitive to heat in terms of degradation of texture, flavor and/or color, the objective being to reduce the time/temperature parameter required for commercial sterilization, which depending upon the foodstuff, involve reducing the equilibrium pH to 4.6 or below or merely reducing an equilibrium pH above 4.6 to a lesser value of 4.6 or above, for example, for corn, from a pH of 6.8 to a pH of 6.1. Examples of low acid foodstuffs are seafood (including fish and shrimp) , meats, meat products (including chili and beef stew) , vegetables, cereal grains (e.g., rice) and cereal grain-based products (including fried rice, Spanish rice and other rice products and pastas (including lasagna, ravioli and spaghetti) . Low acid foodstuffs often require severe thermal processing to achieve commercial sterility, that is, a high temperature, e.g., above 250°F (e.g. to 280°F) for a long time to kill microorganisms responsible for food spoilage and toxicity, and, for some products also to obtain sufficient tenderization. In general, commercial sterilization temperatures and times employed for commercial sterilization of low acid foodstuffs packed in metal containers has ranged from about 230°F to about 275°F, for about from 10 minutes to about 6 hours, the times and temperatures being selectable depending upon the type, amount, conductivity, thermal death time requirement, and initial temperature of the food product, the size of the container, type of sterilization process used, the type of and operating parameters of the equipment employed, as well as energy costs and the throughput desired. For those low acid foods (for example, peas and corn) which are not particularly heat-sensitive when packed in small to medium sized containers, e.g., 303 x 406, corn, for example, in the sense that relatively speaking it can withstand more heat prior to degrading than many other vegetables) , a high temperature, short cook, e.g., 275°F for just enough time to achieve commercial sterility and tenderize the kernels, e.g., an agitated cook of about 10 minutes, is usually employed

SUBSTITUTESHbET because it provides quick throughput and good flavor and texture. However, most low acid foodstuffs are usually processed at lower temperature of from about 240°F to about 255°F for from about 15 to 50 minutes. High temperature, long cooks can tend to cause the most heat-sensitive of the low acid products to degrade in quality as to texture, in terms of their losing their firmness (being overly softened) and losing their integrity, as to flavor by having an overcooked or caramelized taste, and as to color by being darkened as compared to the freshly harvested product. The heat-sensitive products also tend to lose some nutritional value.

Examples of naturally acid foodstuffs include tomatoes, tomato products, and most fruits and berries, such as blueberries. The equilibrium pH of such foodstuffs, which is already below 4.6, is reduced by addition of a suitable acidulant according to the invention, possibly to a pH- of 3.0 or less. (See Example 3) .

Examples of low acid foodstuffs which might be considered heat sensitive for one reason or another include cereal grains, meats and meat products, beans (including lima, kidney, snap beans, e.g. blue lake, green and wax) , and snap bean products (e.g., bean salads), dried bean products (including baked beans, chili), beets, certain seafoods (e.g., shrimp) , yellow squash, zucchini, pumpkin (due to its poor conductivity in large containers, e.g., 603 x 700, it darkens due to the need for a long cook time for sterilization) , carrots, asparagus, cauliflower, melons, eggplant, stir fry Chinese vegetables, cabbage, pasta, celery, mushrooms, olives and onions, and food combinations including one or more of such vegetables. Of the above foodstuffs, squash, zucchini, melons, artichokes, cauliflower and celery are very heat sensitive.

Within the low acid foodstuffs, some such foodstuffs will be suitable for the reduction of the equilibrium pH to 4.6 or below whereas others will not. For example, the equilibrium pH of a low acid foodstuff such as carrots, rice, zucchini, and the like is advantageously lowered to 4.6 or

SUBSTITUTESHEET less prior to thermal processing. However, with regard to low acid foodstuffs with greater natural buffering such as corn, peas, or green beans, it will be difficult to lower the pH of such a foodstuff to 4.6 or below without the addition of an undesirably large quantity of acid and its lactones. It has been found sufficient in such cases to merely lower the equilibrium pH, for example, to a value of from about 4.7 to 5.6.

Acidulants are added to foodstuffs to permit thermal processing of the plastic containers in which they are contained to be effected at lower processing temperatures because of the aforementioned effect of the acid on acid- sensitive microorganisms and its effect on destabilizing bacterial cells. The presence of the acid enhances the lethality of the heat with respect to such microorganisms and cells.

The acidulant is combined with the foodstuff in a conventional manner. If the acid is in solid form, such as granular, it may be sprinkled on the food or intimately mixed therewith. The most preferred procedure is to include the acid in an aqueous solution, called a brine, which is included with the food in the container. With respect to low acid foodstuffs, the amount of acid employed is that which is sufficient to reduce the time/temperature parameter required for commercial sterilization and/or to reduce the equilibrium pH of the food contents to be thermally sterilized as desired e.g., to 4.6 or below. The amount is in part dictated by the pH sought to be obtained and in part by the desired resulting taste of the thermally processed foodstuff. Too much acid would tend to provide the foodstuff with a strongly acidic taste. Typical acids added to foodstuffs include acetic, citric, malic, etc. These acids create a distinct "pickled" flavor. In many instances, the taste of these acids deleteriously detracts from or masks the natural flavor of the product. Thus, pickled beets would have a superior color and texture compared to non-acidified canned beets, but they would not taste like fresh beets. The preferred acidulant to be combined with the foodstuff is a mixture of an acid and its lactones, preferably a mixture of an aldonic acid and its lactones. The preferred aldonic acid is gluconic acid. It is a mild organic acid which has a mild acid taste.

When GDL is used in powdered form, the taste of the powder is initially sweet, and thereafter as it hydrolyses, the taste becomes mildly acidic, of course, when GDL is employed in increasingly large amounts, the foodstuff would tend to taste increasingly acidic, although less acidic than with equivalent amounts of one of the aforementioned acids commonly used in foodstuffs. GDL is preferred because it results in significantly less detraction from or masking of the natural flavor and has less of an acid taste than acids commonly used in foods. Use of an acid/lactone acidulant such as GDL has an added advantage with respect to low acid foods in the sense that it permits their thermal processing in plastic containers at time/temperature parameters even lower than otherwise possible within acceptable limits (from a commercial sterility viewpoint) without the addition of the GDL and with less of an effect on taste than most other acids would produce GDL is commercially available in food grade as a free-flowing, odorless, white powder. Food grade solutions of GDL are also commercially available and can be employed.

This invention does not preclude the addition of other ingredients with the acidulant to the foodstuff/acid combination. For example, small amounts of other acids, for example, citric may be added with GDL to the combination usually in the brine for example to overcome the buffering action (resistance to a change in pH of certain vegetables, such as asparagus) , the amount preferably being minor and below that which would deleteriously affect or mask the taste of the foodstuff. Also salt, sugar, and/or other ingredients may be added to the brine solution or added separately for example for flavor, according to conventional practices.

The plastic containers are filled with the foodstuff/acid/lactone combination and the containers are hermetically sealed, for example, by a conventional double

U3STITUTESHEET seam, typically either under a vacuum or in an atmosphere of steam by liot illing or by passing steam at the container top while sealing. The sealed container is then thermally processed at a temperature of 190°F or higher (usually less than about 240°F) depending upon the factors previously mentioned, to sterilize the container and contents. Thereafter, the container and contents are cooled to ambient temperature, stored and shipped for distribution.

The methods of this invention can be more fully understood by reference to the Drawings and Examples. Reference is now made to Figures 1 through 1H in relation to understanding plastic distortion problems associated with thermal processing plastic containers.

There is shown in Figure 1A an open ended plastic container 1 having sidewalls 3 and a bottom wall 5 which includes a substantially flat portion 7 and outer and inner convex annular rings 9 and 9a with an interstitial ring 9b.

After the container is filled, it is sealed with a top closure 11 as shown in Figure IB, leaving at the container top, a headspace of gases generally designated 13. The containers shown in the drawings are not to be taken as limiting of the scope of the invention, since the containers can be rigid or flexible. Likewise the top closure shown is not to be limiting in that it can be rigid or flexible and it can be made of any suitable material, for example, metal, plastic or a combination thereof.

Figure IC shows container 1 during thermal processing, or after thermal processing but before bottom reforming. As shown in this Figure, the container bottom is outwardly distended because the pressure within the container exceeds the external pressure. If no proper prior measures are taken, after the container is cooled, the bottom wall may remain deformed as shown in Figure ID. Such a container configuration is unstable or undesirable due to rocker bottom. As will hereinafter be explained, rocker bottoms (Figure ID) and sidewall panelling as shown in Figures IE and IF, or both (Figure 1G) , may be minimized or prevented by utilizing the method of this invention wherein lower commercial sterilization processing temperatures and/or times may be employed.

For a full discussion of thermal processing food containers at elevated temperatures, the problems involved and solutions to the problems, see U.S. patent application Serial No. 6/627,703 filed on July 3, 1984, by the same assignee as the assignee of this invention. The disclosure of Serial No. 627,703 is incorporated herein by reference.

Figure 1H represents a desired acceptable container configuration after thermal processing and reforming of the container because it has no rocker bottom or sidewall panelling. This container configuration is the same or nearly the same as the configuration shown in Figure IB.

The present invention and its advantages will now be explained with reference to the following Examples and associated illustrative Figures. For Example 9, the foodstuff was contained in 211 x 215 (2-11/16" in diameter, by 2-15/16" high) multi-layer injection blow molded rigid plastic containers constructed of the following five layers: an outer layer of a 40/60 blend of high density polyethylene and polypropylene, an adhesive layer of a blend of graft copolymers of maleic anhydride and propylene wherein the aleic anhydride moieties are grafted onto the respective polypropylene chains (the blend being comprised of 50% Admer QF 500, 25% QF 550 and 25% of other ingredients including 16% disodium phosphate; the Admers are sold by Mitsui Petrochemical Industries, Ltd.), an oxygen barrier layer of ethylenevinyl alcohol copolymer (EVOH) (sold under the trade designation EVAL-EPF by Kuraray Co., Ltd.), another adhesive layer of the previously mentioned material, and an inner structural layer of the blend of high density polyethylene and polypropylene. The average thickness of the container side wall was .031 inch and of the bottom wall was .011 inch (bottom wall measurements were taken at about the tip of the arrow of lead line for Number 9 in Figure IE) . It is to be understood, however, that the nature of the different layers

TESHEET or whether the plastic container has only one layer or another number of layers, or is of different wall thicknesses, is not per se critical, since the advantages of the lower thermal processing parameters of this invention for the plastic container can be realized for any single plastic container made of another number of layers, another or other plastic material(s), and of different wall thicknesses.

Example 9 Freshly harvested yellow squash, a low-acid foodstuff, was conventionally washed, sliced (each slice approximately 1/2" thick) , and blanched for five minutes in water at about 200°F (a conventional treatment primarily to stop enzyme action) , the blanch being terminated by a cold water rinse. The blanched, sliced yellow squash was filled into a series of the 211 x 215 multi-layer rigid plastic containers to a fill- weight of 5 ounces. Some of the cans were filled with a brine which was an aqueous, solution formed by adding 25.5 grams of GDL and 35 grams of salt in 3 liters of water heated to 180°F'

The initial fill temperature of the container contents was about 110°F and the contents had an equilibrium pH of less than 4.6, namely 4.2. Employing a heated brine helps to rapidly hydrolyze the GDL, which is a benefit. As previously mentioned, when GDL is hydrolyzed, it forms an equilibrium mixture of gluconic acid, glucono-delta lactone and glucono- gamma lactone. Although it is not necessary to heat the brine, heating it is preferred. The cans were hermetically sealed leaving a headspace of 3/16 ;inch, and thermally processed in accordance with this invention to achieve commercial sterility in a still retort at 220°F for 15 minutes to reach a can center temperature (CCT) of 205°F. At the end of the 15 minute cook, when a CCT 205°F had been reached, steam flow into the still retort was terminated. The steam was then vented to the atmosphere, and, via a bottom fill, cooling water at about 70°F was introduced into the retort to cool the containers for about 5 minutes to about 100°F. The water was drained and the containers were removed from the retort. Some of the containers were opened within 24 hours

EET whereupon the equilibrium pH was determined. The resulting thermally processed yellow squash had a firm texture, a bright yellow color, a near fresh home-cooked flavor, and the brine clarity (drained) was clear.

The plastic containers containing the yellow squash thermally processed in Example 9, as would be expected, softened and distended some during the retort thermal processing, however, at 220°F the distention was minimal and significantly less than would have occurred at temperatures of 240°F or higher. Since at 220°F, the CCT of 205°F was reached, overpressure cooling was not needed. During cooling, all containers reformed to a commercially acceptable configuration.

Briefly, Figure 2 shows that when the yellow squash is acidulated to reduce its equilibrium pH to 4.6 or below, the thermal processing time-temperatures which can be employed to achieve commercial sterility of the foodstuff are greatly reduced.

Before referring in more detail to Figure 2 and to Figures 3-7 some general observations should be made about the Figures. In each one (Figures 2-7), speaking in general each curve (to the right) shows a parameter curve which gives an indication of the various time-temperature combinations which will achieve commercial sterility of the particular foodstuff mentioned when thermally processed without an acidulant in a multi-layer plastic container of the size specified. These curves are based upon heat penetration characteristics data derived from a heat penetration test with the particular product and container size, and a certain time-temperature data point along each right hand curve corresponds to time- temperature thermal processing conditions actually used by the assignee of this invention in reaching commercially sterility with the specified foodstuff without GDL in the specified container size and retort. Each parameter curve to the left gives an indication of the various time-temperature combinations calculated to achieve commercial sterility of the particular foodstuff mentioned when thermally processed with

T an acidulant in the same multi-layer plastic container. The left curves are based upon the same heat penetration characteristics data as used for its associated right hand curve but with the additional critical factor that foodstuff contents are acidified with an acidulant to have an equilibrium pH of 4.6 or below when thermally processed. The left hand curves are calculated to achieve a can center temperature (CCT) of 205°F, which is sufficient for achieving commercial sterility of all acidified foods.

It is to be noted that Figures 2-7 are logarithmic and merely illustrative of the dramatic movement of the parameter to the left under this invention, and, therefore those skilled in the art will understand that the parameters illustrated are not precisely interpretable and are not to be used for selection of a particular actual thermal process time and temperature.

Referring now to Figures 2-7 in greater detail, Figure 2 shows the shift to the left of a still retort thermal processing parameter curve to achieve commercial sterility of yellow squash, the shift being from the right curve figured at an F₀ of 3.7 without an acidulant having been added, to the left curve calculated to achieve a can center temperature (CCT) of 205°F which is also sufficient to achieve commercial sterilization of the product, and which for this product would be equivalent to a calculated F_Q of .01.

Example 9 and Figure 2 demonstrate that the addition of an acidulant, here GDL, to a yellow squash foodstuff to be canned permits a significant reduction in the severity of the thermal process to achieve commercial sterility of the contents, in that the thermal processing temperature, as well as the time, are significantly reduced with respect the heat- sensitive plastic material of which the container is made. The scope of the change can be appreciated by reference to Figure 2. In achieving the same the state of sterilization, for the same product in the same container with the same retort, whereas the right curve shows that without practicing this invention, the thermal process to which the plastic would be subjected typically would be about 240°F for about 36 to 40 minutes, the left curve shows that under this invention the plastic need only see 220°F for about 15 minutes. It is to be noted that the chart clearly shows that for time through-put, energy and economic reasons, as well as the increased likelihood of overcooking the product, it would be commercially impractical to process yellow squash in a plastic container at 220°F without an acidulant, for at that temperature it would take as long as 200 minutes to thermally process the same yellow squash.

The temperature/time parameters of each curve to the right in the Figures are based upon a particular sterilizing value (F₀) for the particular product which value here is basically a time equivalent calculated at 250°F. Particular F₀ values required to achieve commercially acceptable shelf- stable sterility are highly variable depending upon type and size of the container, type and size of food product, acidity of the product and the like. Reference is directed to the publication "Calculation of Processes for Canned Foods", Copyright 1967, American Can Company, which is an American Can Company Technical Services Publication, for further information on this matter, and how F₀ values are derived by those skilled in the art. The higher the F₀ value, the greater the severity of the thermal process. Generally speaking, the lower the pH, the less severe the heat treatment required for thermal sterilization.

Those skilled in the art of thermally processing foodstuffs whose heating characteristics have been established, can determine by known calculations (available in the aforementioned Publication) , a sterilizing value (here, for example, CCT) which will achieve commercial sterility for the acidulated product in question and the type of retort or process to be employed. For products which heretofore never have been commercially sterilized and canned or for which no heating characteristics have been developed, it is recommended that an established thermal processing authority such as the assignee of this invention be consulted to obtain a sterilizing value (here against for example, CCT) which will achieve commercial sterility for the equilibrium pH of the particular acidulated product contents to be processed. For all products whose equilibrium pH have been lowered to 4.6 or below, a CCT of 205°F can be employed for commercial sterility. Should it be desired to use a CCT of less than 205°F, an aforementioned authority should be consulted to determine whether the lower CCT temperature would be sufficient to obtain commercial sterility.

The can or container center temperature (CCT) is determined by implanting a thermocouple into the container prior to its being hermetically sealed and tested. CCT herein mean the temperature at the slowest heating point of the food product in the container which, depending on the food product, may be but not necessarily is the actual center point of the container.

Figure 3 shows the shift to the left of a still retort processing parameter curve to achieve commercial sterility of diced carrots in 401 x 407 thermoformed multi-layer rigid plastic containers, the shift being from the right curve wherein carrots were thermally processed at an F₀ of 3.5 without an acidulant, to the left curve which is based on an initial fill temperature of 100°F, is calculated to achieve a CCT of 205°F, and which, for this product, would be equivalent to an F₀ of .01. This curve indicates that whereas thermal processing of diced carrots would usually be conducted at, for example, 2 0°F for about 30 minutes, using an acidulant combined with the food in accordance with this invention, the plastic containers need only be subjected to 220°F for 12 minutes. It is to be noted that carrots are exemplary of a low acid foodstuff which is heat sensitive, and, due to higher thermal processing temperatures, e.g., 240°F for 30 minutes, the sterilized carrots suffer some degradation in organoleptic quality in that they exhibit a slightly darkened orange color, a slightly caramelized (burnt) flavor, and a slightly flaccid texture. By contrast, and in line with a specific objective of this invention, carrots processed with an acidulant at the lower temperature of 220°F for about 12 minutes exhibit a bright orange color, a more fresh-like flavor and a firm texture, and the overall organoleptic effect is improved despite the possibility of a slightly acidic flavor.

Figure 4 shows the shift to the left of a still retort processing parameter curve for achieving commercial sterility of green beans in 303 x 406 multi-layer rigid plastic containers, the shift being from the right curve with respect to which the green beans were thermally processed at an F₀ of 2.8 without an acidulant, to the left curve which is based on an initial fill temperature of 100°F, is calculated to achieve a CCT of 205°F, and which for this product would be equivalent to an F₀ of .01. Since commercial canning of green beans in metal cans often occurs at temperatures of 255°F, reference to the right curve of Figure 4 indicates that at that temperature a process of approximately 17 minutes in 303 x 406 plastic containers would be needed to reach commercial sterility in a still retort. At a retort temperature of 255°F, container walls of polyolefiή based materials such as polyethylene and other structural materials previously described will soften to the point where distortion or crushing can often occur, especially in the bottom layers of the retort. These problems could be reduced by selecting a process along the right hand curve with a lower temperature parameter, e.g., at 240°F for 27 minutes. However, at this temperature, a retort overpressure during cooling would probably still be needed and the headspace and other container and process variables must be carefully controlled to avoid occasional distortion problems. Also, the longer cook, 27 minutes versus 17 minutes, would reduce product throughput in the retort.

A better solution to the elimination of plastic container distortion in this example would be to utilize an acidulant such as GDL according to the present invention, thus allowing the achievement of commercial sterility along the left curve in Figure 4. This would allow use of significantly lower retort temperatures and times such as, e.g., 220°F for 12 minutes. This parameter significantly reduces plastic distortion, increases retort throughput (12 minutes vs. 17 or 27 minutes) and produces canned beans with firmer texture and less of an overcooked or caramelized flavor, as well as better retention of heat-sensitive nutrients.

Figure 5 shows the shift to the left which can be obtained in accordance with this invention of a still retort processing parameter curve for thermally sterilizing green peas in 303 x 406 multi-layer rigid plastic containers, the shift being from the right curve wherein the thermal processing was effected at an F₀ of 6.0 without an acidulant, to the left curve which is based on an initial fill temperature of 100°F, and is calculated to achieve a CCT of 205°F which for this product, would be equivalent to an F₀ of .01. A comparison of the curves shows that whereas plastic containers packed with green peas would be thermally processed, e.g., at about 240°F for about 53 minutes, an equivalent commercial sterility could be achieved with an acidulant in a plastic container which, according to this invention, would only be subjected to 220°F for about 11 minutes.

As examples using a different retort, two packs were made with green peas in 303 x 406 multi-layer rigid plastic cans which were thermally processed in a Steritort, which rotates the cans during cooking. For the first pack, a 260°F, 15 minute cook was used. The packed cans had an acceptable configuration (including good double seam integrity) , The second pack, cooked at 265°F for 13 minutes to obtain faster throughput, was a failure because the double seams unrolled and destroyed the packages' integrity. The curves and the above packs show that a better solution to the need for higher throughput would be to acidulate the green peas and process them at a temperature of 220°.

Example 10 Freshly harvested corn was conventionally washed and overblanched. 63 cc's of cold salt-containing brine was filled into each of a series of 303 x 406 thermoformed, multi¬ layer rigid plastic containers. 10.5 ounces of the blanched corn was added to each of a series of the containers. Then, 5 weight ounces of 190°F water was added to top the cans off leaving a headspace of 3/16 of an inch. The containers were steam flow hermetically sealed and thermally processed in an agitated retort (Steritort) at a 6.3 RPM reel speed to achieve commercial sterility at 255°F for 20 minutes. The resulting thermally processed corn was of good quality.

Although an overpressure of 10 psi was employed during cooling due to poor material distribution in the container wall, a fair number of the thermally processed plastic containers were panelled and therefore did not have a commercially acceptable configuration.

Figure 6 shows the shift to the left of an agitated retort processing parameter curve for commercially sterilizing corn, the shift being from the right curve with respect to which one data point represents wherein the corn was actually thermally processed in Example 10 at an F₀ of at least 10. without an acidulant to the left curve which is based on an initial fill temperature of 100°F and calculated to achieve a can center temperature of 205°F, which for this product would be equivalent to an F_Q of .01. Again, whereas the plastic containers conventionally thermally processed in accordance with Example 10 were subjected to temperatures of about 255°F for about 20 minutes, an equivalent thermal sterilization of the product could be achieved in accordance with this invention by subjecting the containers to about 230°F for about 8 minutes, or to about 220°F for about 10 minutes. It has been found, however, that the amount of acidulant needed to obtain these reduced thermal processing parameters produces corn whose color and texture were good but whose flavor was acidic. (See Example 4 where a low amount of acidulant produced good flavor.

Figure 7 shows the shift to the left which can be effected in accordance with this invention of a still retort processing parameter curve for commercially sterilizing lasagna, the shift being from the right curve wherein the lasagna thermally processed at an F₀ of 8.3 without an acidulant, to the left curve which is based on initial fill temperature of 100°F, and is calculated to achieve a CCT of 205°F, which for this product would be equivalent to an F₀ of .03. The Figure shows that whereas the plastic container in which the lasagna would be commercially sterilized, for example, at 240°F for about 100 minutes, an equivalent sterilization can be obtained with an acidulant in a plastic container which in accordance with this invention would only be subjected to 220°F for about 48 minutes.

Example 11 Canned lasagna is currently often thermally processed commercially in metal containers in still retorts at 240°F. The packer wants to process it at 250°F to achieve a higher throughput.

With respect to plastic containers, test packs of lasagna were prepared in the plastic cans of Example 9 (i.e., 211 x 215) and processed in a still retort both at 240°F and at 245°F, using a 10 psi air overpressure during the cooling stage. The cans were stacked 13 layers high. The lower cans easily support this load at room temperature. With respect to the cans of a crate ..hich were processed in the retort at 245°F, for 80 minutes, the cans of the bottom 3 layers exhibited crushing (of the bearing ring, just outward from the tip of the arrow of the lead line for No. 9 at the resr_.ng point of the container in Figure 1A) .

As for the cans of a crate which were processed at 240°F for 100 minutes, crushing was confined to the bottommost layer of the stack. Even though this is a longer cycle time, better can quality would necessitate using a 240°F cook for non- acidulated lasagna when using this type of retort. It can be seen from the right cure of Figure 7, the packer's objective of processing at 250°F to obtain a high throughput still requires a cook time of about 70 minutes and therefore the objective cannot be reached with these particular can and this load in this type of retort. However, the left curve of Figure 7 shows that with acidulated lasagna, the objective can be met in that the process time can be reduced to about 48 minutes using a 220°F cook. Under these conditions, it can be seen that since the lower cans had significantly better crush resistance at 240°F than at 245°F, it is evident that at 220°F the lower cans will not crush and a fast cycle time can be achieved.

The multi-layer rigid plastic containers used as a basis for calculating the curves of Figures 2-7 were five layer constructions whose layers were similar to those of the containers of Example 9 in that the outer and inner layers were blends of high density polyethylene and polypropylene, the barrier was an EVOH material and the adhesive was not a blend of Admer materials but was a single adhesive material.

With respect to the cook cycle techniques which would be employed in accordance with this invention, from the start of the steam cook until the end of the cook when the steam is turned off, the thermal processing techniques (other than with respect to temperatures and times) , which would be employed with respect to plastic containers, need not be but they can be basically the same as those which would be employed for thermally processing the respective foodstuffs in plastic or metal containers of the same size (with or without an acidulant) . With respect to temperatures and times, under this invention, if the conventional elevated temperature is not problematical due to either or both the foodstuff or the plastic container, within limits required for achieving commercial sterility, the time can be shortened to thereby achieve consequent increased throughput and obvious economic and energy savings. If temperature is problematical to the product and/or to the plastic, the temperature can be lowered as desired within limits required for commercial sterility and within limits of the equipment, and with respect to certain products within the time limits needed to sufficiently cook the product, e.g. , for firm products to obtain adequately softened texture. Heretofore, for achieving commercial sterility of low acid foods in plastic containers, the desired thermal processing temperature range would have been from about 240°F to about 265°F, preferably to about 255°F, just as with metal containers. For most such products, processing at below 240°F would take too long to achieve commercial sterility. Increasingly, from about 255°F to 265°F the structural material tends to become so softened that distortion becomes increasingly problematical both in terms of distortion and crush resistance (in a still retort) and reformation becomes more difficult. In one test done with green peas in an agitated cook (Steritort) (at an 8 RPM reel speed) at 265°F for 13 minutes all the double seams of the (303 x 406) multi-layer rigid plastic containers unfolded. At 260°F for 15 minutes, with closely controlled overpressure cooling, 9 out of 125 containers panelled.

In accordance with this invention, plastic containers can be thermally processed to achieve commercial sterility of the packaged foodstuff at temperatures below 240°F, preferably from about 220°F to about 240°F. Of course, the temperature/time employed will depend upon many factors as previously mentioned. Other things being equal, the time required for thermal processing plastic containers is longer than for metal containers because plastic does not conduct heat as well as metal. At the end of the thermal sterilization cycle, as in the case with plastic containers processed without an acidulant, any plastic wall distortion must reform. Reformation is done while the plastic of the bottom wall is at a reformable temperature, and can be achieved by causing the pressure outside of the container to exceed the pressure inside of the container, either by utilizing an added external pressure or by reducing the pressure inside the container. In accordance with this invention, as demonstrated by Example 9 and as illustrated by the left hand curves in Figures 2-7, since a CCT of only 205°F need be achieved for commercial sterilization of an acid or acidified foodstuff, and since foodstuffs develop high internal pressures at 212°F or -above, depending on the various factors involved, in many instances an overpressure cool may not need to be employed. For example, generally, there tends to be less need or desire for an overpressure cool for an agitated rotary cook than for a still cook. Less plastic container time in an agitation environment advantageously reduces chances of abrasion of the container wall surfaces. It has been found that as a general guideline for still cooking, depending of course on the factors involved, in many instances an overpressure cool may not be needed at temperatures below about 230°F, but, at temperatures above about 230°F, it may be desirable to use some overpressure.

Above about 230°F, about 10 psi overpressure (over the cook pressure inside the retort equipment) has been found satisfactory. For example, should an overpressure cool be desired for a still retort in a situation in which there has been a cook temperature of 240°F with an internal retort pressure of 10.5, air or some inert gas is introduced into the retort before cooling. About 10 psi over above the internal retort pressure has been found satisfactory for acceptable bottom wall reformation. After the bottom is reformed and the air pressure is removed by venting to atmospheric, the water cooling process can be employed according to conventional practices it being appreciated of course that with the lower cook temperatures hereunder, less cooling time is needed. From the above, it can be seen that, by reducing the thermal sterilization temperature, need for a pressure cool and for staying within an allowable pressure cool psi/time range may be eliminated while still obtaining acceptable reformation and good container aesthetics.

As previously stated, an advantage provided by this invention is that the lower processing temperature mean less criticality as to filling conditions in terms of controlling the head-space to within an acceptable range because of the affect of headspace on internal gas pressures imposed on the container wall during the thermal sterilization cycle. Although it is not to be taken as directly analogous to foodstuffs, the broadening of the useful head-space range as cook temperature decreases can be somewhat illustrated by the fact that in the case of water hermetically sealed in 211 x 215 multi-layer rigid, plastic containers, at 265°F the head- space must be kept between 8cc - lOcc. If less, there are rocker bottoms and if more, there is panelling. At 260°F, the range is between 6cc - lOcc; at 255°F it is between 4cc - lOcc; and at 240°F, it is between 2cc - 14cc. It might be expected that the useful head-space range would be broadened at lower temperatures for water or for food. It is to be noted that in Example 9 (squash, cooked at 220°F) , acceptable configurations were obtained with 20 cc headspace.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it is apparent that various changes may be made in the steps of the methods and in the structures and materials described without departing from the spirit and scope of the invention or sacrificing its material advantages, the methods and the structures and materials herein before described being merely preferred embodiments thereof.

Claims

E C L A I M :

1. A method of thermally processing an acid foodstuff, which comprises: combining the foodstuff with a mixture consisting essentially of an acid and its lactones or a pre¬ cursor of said mixture in an amount sufficient to lower the equilibrium pH, and subjecting the food¬ stuff to a time-temperature parameter sufficient to achieve commercial sterilization thereof, said parameter being lower than the higher commercial sterilizing parameter needed when an acid and its lactones or said precursor are not present, whereby one or more of the organoleptic texture, color, or flavor properties of said foodstuff are improved compared to said properties when said lower parameter or said acid and its lactones are not employed.

2. A method according to Claim 1 in which the foodstuff is selected from the group consisting of tomatoes, fruits, and berries.

3. A method according to Claim 1 in which the lowered equilibrium pH is in the range of from about 2.7 to 4.3.

4. A method according to Claim 1 in which commercial sterilization is accomplished while the foodstuff is in a hermetically sealed container.

5. A method according to Claim 1 in which commercial sterilization is effected by heating at a temperature in the range of from about 170°F to about 230°F.

6. A method of thermally processing an acid, heat- sensitive foodstuff susceptible to degradation when thermally processed, which comprises: combining the foodstuff with a mixture consisting essen¬ tially of an aldonic acid and its lactones or a precursor thereof in an amount sufficient to lower the equilibrium pH, and subjecting the foodstuff to a time-temperature parameter sufficient to achieve commercial sterilization thereof, said parameter being lower than the higher commercial sterilization

SUESTITUTE SHEET parameter needed when an aldonic acid and its lactones are not present, and the lower parameter and said aldonic acid and its lactones exerting a combined effect whereby at least one of the organoleptic texture, flavor, or color qualities of the foodstuff is improved compared to that obtained at the higher parameter or in the absence of said aldonic acid and its lactones.

7. A method according to Claim 6 in which the foodstuff is selected from the group consisting of tomatoes, fruits, and berries.

8. A method according to Claim 6 in which the lowered equilibrium pH is in the range of from about 2.7 to 4.3, and in which commercial sterilization is accomplished while the foodstuff is in a hermetically sealed container.

9. A method according to Claim 6 in which commercial sterilization is effected by heating at a temperature in the range of from about 170oF to about 230°F.

10. A method of thermally processing an acid foodstuff, which comprises: filling a container with foodstuff and a mixture consist¬ ing essentially of an aldonic acid and its lactones or a precursor of said mixture in an amount sufficient to lower the equilibrium pH; and hermetically sealing the container and subjecting the sealed contents to a time-temperature parameter sufficient to commercially sterilize the contents, said parameter being lower than the higher commercial sterilizing parameter needed when an aldonic acid and its lactones are not present, said lower parameter and said aldonic acid and its lactones exerting a combined effect whereby there is improvement in at least one of the organoleptic properties of the foodstuff compared to said properties obtained in the absence of said lower parameter or said aldonic acid and its lactones.

11. A method according to Claim 10 in which the foodstuff is selected from the group consisting of tomatoes, fruits, and berries.

12. A method according to Claim 10 in which the lowered equilibrium pH is in the range of about 2.7 to 4.3.

13. A method according to Claim 10 in which commercial sterilization is effected by heating at a temperature in the range of from about 170°F to about 230°F.

14. A method of thermally processing an acid foodstuff susceptible to degradation in color, texture, or flavor when thermally processed, which comprises: filling a container with the foodstuff and a mix¬ ture consisting essentially of an aldonic acid and its lactones or a precursor of said mixture in an amount sufficient to lower the equilibrium pH; and hermetically sealing the container and subjecting the sealed contents to a time-temperature parameter sufficient to commercially sterilize the contents, said parameter being lower than the higher commercial sterilizing parameter needed when an aldonic acid and its lactones are not present, the combination of said lower parameter and said aldonic acid and its lactones being responsible for more nearly retaining the natural color, texture, or flavor of the foodstuff compared to the higher parameter in the absence of acid or to the lower parameter when said aldonic acid and its lactone are not employed.

15. A method according to Claim 14 in which the foodstuff is selected from the group consisting of tomatoes, fruits, and berries.

16. A method according to Claim 14 in which the lowered equilibrium pH is in the range of from about 2.7 to 4.3.

17. A method according to Claim 14 in which commercial sterilization is effected by heating at a temperature in the range of from about 170°F to about 230°F.

18. A hermetically sealed container containing a commercially sterilized acid foodstuff and a mixture consisting essentially of an acid and its lactones which lowers the equilibrium pH of the foodstuff, and in which the texture of the foodstuff is firmer and its color is closer to that of the natural product as compared to the same foodstuff commercially sterilized without an acid and its lactones.

19. A hermetically sealed container according to Claim 18 in which the foodstuff is selected from the group consisting of tomatoes, fruits, and berries.

20. A hermetically sealed container according to Claim 18, sterilized at a temperature of 170°F or higher.

21. A hermetically sealed container containing a commercially sterilized acid foodstuff and glucono-delta lactone which lowers the equilibrium pH of the foodstuff, and in which the texture, color, or taste of the foodstuff is closer to that of the natural product as compared to the same foodstuff commercially sterilized without GDL.

22. A hermetically sealed container according to Claim 21 in which the foodstuff is selected from the group consisting of tomatoes, fruits, and berries.

23. A method according to Claim 1, wherein the foodstuff is combined with a mixture of gluconic acid, glucono-delta lactone, and glucono-gamma lactone.

24. A method according to Claim 5 or 13, wherein the heating takes place in an open kettle.

25. A method according to Claim 5 or 13, wherein the heating takes place in a retort.

26. A method according to Claim 6, wherein the foodstuff is combined with glucono-delta lactone in admixture with its hydrolysis products.

27. A thermally processed foodstuff prepared according to the method of Claim 1.

28. A method according to Claim 1, wherein the acid and its lactones are provided by a combination of an aldonic acid salt and a strong acid.

29. A method according to Claim 28, wherein the aldonic acid salt is a sodium, potassium, or calcium salt.

30. A method according to Claim 28, wherein the strong acid is hydrochloric acid.

31. A method according to Claim 1, wherein the acid and

SUBSTITUTESHEET its lactones comprise an equilbrium mixture of gluconic acid, glucono-delta lactone, and glucono-gamma lactone.

32. A method of thermally processing an acid foodstuff susceptible to heat degradation of color and/or texture and/or flavor to provide a commercially sterile product in which the color and/or texture and/or flavor are substantially retained, which process comprises the steps of:

(a) contacting the foodstuff with an aldonic lactone or a hydrolysis mixture consisting essen¬ tially of an aldonic acid and its lactones or a pre¬ cursor thereof in an amount sufficient to lower the equilibrium pH of the foodstuff, to form a mixture thereof, and

(b) heating the mixture from step (a) at a time-temperature parameter sufficient to achieve commercial sterilization of said mixture and to produce an equilibrium mixture of unreacted aldonic acid and its lactones, the time-temperature parameter being substantially less than it would be to attain commercial sterilization in the absence of the aldonic acid and its lactones and the color and/or texture and/or taste of the foodstuff being substantially retained.

33. A method according to Claim 32, wherein the foodstuff is contacted with glucono-delta lactone or a hydrolysis mixture of gluconic acid, glucono-delta lactone, and glucono- gamma lactone.

34. A method of thermally processing a low acid foodstuff susceptible to heat degradation of color and/or texture and/or flavor to provide a commercially sterile product in which the color and/or texture and/or flavor are substantially retained, which process comprises the steps of:

(a) contacting the foodstuff with a mixture consisting essentially of an aldonic acid having six carbon atoms and its lactones or a precur¬ sor thereof in an amount sufficient to lower the equilibrium pH of the foodstuff, to form a mixture thereof;

(b) hermetically sealing the mixture from step (a) in a heat-resistant container; and

(c) heating the container from step (b) at a time-temperature parameter sufficient to commercially sterilize the contents of the container and to produce an eqilibrium mixture of said aldonic acid and its lactones, whereby the color and/or texture and/or taste of the foodstuff is not substantially changed and the time-temperature parameter is substantially less than it would be to attain commercial sterility in the absence of the aldonic acid and its lactones.

35. A method according to Claim 34, wherein said aldonic acid is selected from the group consisting of galactonic, gluconic, and gluconic acids and said precursor is selected from the group consisting of the corresponding lactone or lactones.

36. A thermally processed foodstuff prepared according to the method of Claim 32.

37. A hermetically sealed container containing thermally processed foodstuff, prepared according to the method of Claim 34.

38. A hermetically sealed container containing a commercially sterilized, acid foodstuff susceptible to heat degradation of color and/or texture and/or flavor and a mixture consisting essentially of an aldonic acid having six carbon atoms and its lactones in an amount sufficient to lower the equilibrium pH of the foodstuff, the color and/or texture and/or flavor of the foodstuff being closer to that of the unprocessed foodstuff or the foodstuff exhibiting less degradation in organoleptic properties than that exhibited by the same foodstuff commercially sterilized in the absence of the lower parameter and the aldonic acid and its lactones.

39. A hermetically sealed container according to Claim 38, wherein the aldonic acid and its lactones comprise a mixture selected from the group consisting of (1) galactonic acid, galactono-delta lactone, and galactono-gamma lactone, (2) gluconic acid, glucono-delta lactone, and glucono-gamma lactone, and (3) gulonic acid, gulono-delta lactone, and gulono-gamma lactone.

40. A method of thermally processing an acid foodstuff, which comprises: filling a container with the foodstuff and a brine solution consisting essentially of glucono-delta lactone, glucono- gamma lactone, and gluconic acid in an amount sufficient to lower the equilibrium pH; hermetically sealing the container and subjecting the sealed contents to a time-temperature parameter sufficient to commercially sterilize the contents, and to achieve a sterilizing value indicated by a can center temperature (CCT) of 205°F or less.

41. A method according to Claim 40, wherein the brine is preheated.

42. A method according to Claim 41, wherein the brine is preheated to a temperature of about 190°F.

43. A method according to Claim 41, wherein the container is a metal can.

44. A method according to Claim 40, wherein a sterilizing value indicated by a CCT of 205°F or less is obtained by heating said sealed container at a temperature of from about 170oF to about 230oF.

45. A method according to Claim 44, wherein the foodstuff is blanched in a liquid at a temperature of from about 170°F to 200°F and rinsed with cold water to terminate the blanch prior to being filled into said container.

46. A method according to Claim 1 in which the equilibrium pH is lowered to 4.3 or less.

47. A method according to Claim 2, 7, 11, or 15 in which the foodstuff is tomatoes or blueberries.

48. A hermetically sealed container according to Claim 19 or 22 in which the foodstuff is tomatoes or blueberries.

49. A hermetically sealed container according to Claim 18, wherein the equilibrium pH of the foodstuff is lowered to

SUBSTITUTE SHEET 4.3 or less.

50. A hermetically sealed container according to Claim 49, wherein the equilibrium pH of the foodstuff is lowered to from about 2.7 to 4.3.

51. A method of thermally processing a low acid foodstuff having high natural buffering capacity, which comprises: combining the foodstuff with a mixture consisting essentially of an acid and its lactones or a precursor of said mixture and subjecting the foodstuff to a time-temperature parameter sufficient to achieve commercial sterilization thereof, the amount of said acid and its lactones being sufficient to effect an improvement in one or more of the organoleptic texture, color, or flavor properties of said foodstuff compared to said properties when said acid and its lactones are not employed.

52. A method according to Claim 51 in which commercial sterilization is effected by heating at a temperature in the range of from about 212°F to about 270°F.

53. A method of thermally processing a low acid, heat- sensitive foodstuff having high natural buffering capacity and susceptible to degradation when thermally processed, which comprises: combining the foodstuff with a mixture consisting essen¬ tially of an aldonic acid and its lactones or a precursor thereof, and subjecting the foodstuff to a time-temperature parameter sufficient to achieve commercial sterilization thereof, said parameter being lower than the higher commercial sterilization parameter needed when an aldonic acid and its lactones are not present, and the lower parameter and said aldonic acid and its lactones exerting a combined effect whereby at least one of the organoleptic texture, flavor, or color qualities of the foodstuff is improved compared to that obtained at the higher parameter or in the absence of said aldonic acid and its'lactones.

54. A method according to Claim 51 or 53 in which a sufficient amount of acid and its lactones are present to obtain an equilibrium pH in the range of from about 4.6 to 5.7, and in which commercial sterilization is accomplished while the foodstuff is in a hermeti-cally sealed container.

55. A method according to Claim 53 in which commercial sterilization is effected by heating at a temperature in the range of from about 212°F to about 270°F.

56. A method of thermally processing a low acid foodstuff having high natural buffering capacity, which comprises: filling a container with foodstuff and a mixture consisting essentially of an aldonic acid and its lactones or a precursor of said mixture in an amount sufficient to obtain an equilibrium pH of 4.6 or above; and hermetically sealing the container and subjecting the sealed contents to a time-temperature parameter sufficient to commercially sterilize the contents, said parameter being lower than the higher commercial sterilizing parameter needed when an aldonic acid and its lactones are not present, said lower parameter and said aldonic acid and its lactones exerting a combined effect whereby there is improvement in at least one of the organoleptic properties of the foodstuff compared to said properties obtained in the absence of said lower parameter or said aldonic acid and its lactones.

57. A method according to Claim 56 in which the foodstuff is corn and in which commercial sterilization is effected by heating at a temperature in the range of from about 212°F to about 270°F.

58. A method of thermally processing a low acid foodstuff having high natural buffering capacity and susceptible to degradation in color, texture, or flavor when thermally processed, which comprises: filling a container with the foodstuff and a mixture consisting essentially of an aldonic acid and its lactones or a precursor of said mixture in an amount sufficient to obtain an equilibrium pH of 4.6 or above; and hermetically sealing the container and subjecting the sealed contents to a time-temperature parameter sufficient to commercially sterilize the contents. said parameter being lower than the higher commercial sterilizing parameter needed when an aldonic acid and its lactones are not present, the combination of said lower parameter and said aldonic acid and its lactones being responsible for more nearly retaining the natural color, texture, or flavor of the foodstuff compared to the higher parameter in the absence of acid or to the lower parameter when said aldonic acid and its lactone are not employed.

59. A method according to Claim 51, 53, 56, or 58 in which the foodstuff is selected from the group consisting of corn, peas, and green beans.

60. A method according to Claim 56 or 58 in which the equilibrium pH obtained is in the range of from about 4.6 to 5.7.

61. A method according to Claim 58 in which commercial sterilization is effected by heating at a temperature in the range of from about 212°F to about 270°F.

62. A hermetically sealed container containing a commercially sterilized low acid foodstuff having high natural buffering capacity and a mixture consisting essentially of an acid and its lactones which imparts to the contents an equilibrium pH of 4.6 or above, and in which the texture of the foodstuff is firmer and its color is closer to that of the natural product as compared to the same foodstuff commercially sterilized without an acid and its lactones.

63. A hermetically sealed container according to Claim 62, sterilized at a temperature of 212°F or higher.

64. A hermetically sealed container containing a commercially sterilized low acid foodstuff having high natural buffering capacity and glucono-delta lactone which imparts to the contents an equilibrium pH of 4.6 or above, and in which the texture, color, or taste of-the foodstuff is closer to that of the natural product as compared to the same foodstuff commercially sterilized without glucono-delta lactone.

65. A hermetically sealed container according to Claim 62 or 64 in which the foodstuff is selected from the group consisting of corn, peas, and green beans.

66. A method according to Claim 51, wherein the foodstuff is combined with a mixture of gluconic acid, glucono-delta lactone, and glucono-gamma lactone.

67. A method according to Claim 52, 55, 57, or 61, wherein the heating takes place in a retort.

68. A method according to Claim 53, wherein the foodstuff is combined with glucono-delta lactone in admixture with its hydrolysis products.

69. A thermally processed foodstuff prepared according to the method of Claim 51.

70. A method according to Claim 51, wherein the acid and its lactones are provided by a combination of an aldonic acid salt and a strong acid.

71. A method according to Claim 70, wherein the aldonic acid salt is a sodium, potassium, or calcium salt.

72. A method according to Claim 70, wherein the strong acid is hydrochloric acid.

73. A method according to Claim 51, wherein the acid and its lactones comprise an equilbrium mixture of gluconic acid, glucono-delta lactone, and glucono-gamma lactone.

74. A method of thermally processing a low acid foodstuff having high natural buffering capacity and susceptible to heat degradation of color and/or texture and/or flavor to provide a commercially sterile product in which the color and/or texture and/or flavor are substantially retained, which process comprises the steps of:

(a) contacting the foodstuff with an aldonic lactone or a hydrolysis mixture consisting essentially of an aldonic acid and its lactones in an amount sufficient to obtain an equilibrium pH of about 4.6 or above of the foodstuff, to form a mixture thereof, and

(b) heating the mixture from step (a) at a time- temperature parameter sufficient to achieve commercial sterilization of said mixture and to produce an equilibrium mixture of unreacted aldonic acid and its lactones, the time- temperature parameter being substan-tially less than it would be to attain commercial sterilization in the absence of the aldonic acid and its lactones and the color and/or texture and/or taste of the foodstuff being substantially retained.

75. A method according to Claim 74, wherein the foodstuff is contacted with glucono-delta lactone or hydrolysis mixture of a gluconic acid, glucono-delta lactone, and glucono-gamma lactone.

76. A method of thermally processing a low acid foodstuff having high natural buffering capacity and susceptible to heat degradation of color and/or texture and/or flavor to provide a commercially sterile product in which the color and/or texture and/or flavor are substantially retained, which process comprises the steps of:

(a) contacting the foodstuff with a mixture consisting essentially of an aldonic acid having six carbon atoms and its lactones or a precursor thereof in an amount sufficient to obtain an equilibrium pH of the foodstuff of from about 4.6 to 5.7, to form a mixture thereof;

(b) hermetically sealing the mixture from step (a) in a heat resistant container; and

(c) heating the container from step (b) at a time- temperature parameter sufficient to commercially sterilize the contents of the container and to produce an eqilibrium mixture of said aldonic acid and its lactones, whereby the color and/or texture and/or taste of the foodstuff is not substantially changed and the time-temperature parameter is substantially less than it would be to attain commercial sterility in the absence of the aldonic acid and its lactones.

77. A method according to Claim 76, wherein said aldonic acid is selected from the group consisting of galactonic, gluconic, and gluconic acids and said precursor is selected from the group consisting of the corresponding lactone or lactones.

78. A thermally processed foodstuff prepared according to the method of Claim 74.

79. A hermetically sealed container containing thermally processed foodstuff, prepared according to the method of Claim 76.

80. A hermetically sealed container containing a commercially sterilized, low acid foodstuff having high natural buffering capacity and susceptible to heat degradation of color and/or texture and/or flavor and a mixture consisting essentially of an aldonic acid having six carbon atoms and its lactones in an amount sufficient to obtain an equilibrium pH of the foodstuff of 4.6 or above, the color and/or texture and/or flavor of the foodstuff being closer to that of the unprocessed foodstuff or the foodstuff exhibiting less degradation in organoleptic properties than that exhibited by the same foodstuff commercially sterilized in the absence of the lower parameter and the aldonic acid and its lactones.

81. A hermetically sealed container according to Claim 80, wherein the aldonic acid and its lactones comprise a mixture selected from the group consisting of (1) galactonic acid, galactono-delta lactone, and gal ctono-gamma lactone, (2) gluconic acid, glucono-delta lactone, and glucono-gamma lactone, and (3) gluconic acid, glucono-delta lactone, and glucono-gamma lactone.

82. A method of thermally processing a low acid foodstuff having high natural buffering capacity, which comprises: filling a container with the foodstuff and a brine solution consisting essentially of glucono-delta lactone, glucono-gamma lactone, and gluconic acid in an amount sufficient to obtain an equilibrium pH of 4.6 or above; hermetically sealing the container, and subjecting the sealed contents to a time-temperature parameter sufficient to commercially sterilize the contents, and to achieve a sterilizing value indicated by a can center temperature (CCT) of 205°F or above.

83. A method according to Claim 82, wherein the brine is preheated.

84. A method according to Claim 83, wherein the brine is preheated to a temperature of about 190°F.

85. A method according to Claim 83, wherein the container is a metal can.

86. A method according to Claim 82, wherein a sterilizing

C--i,»E__-.P—T^■ value indicated by a CCT of 205°F or above is obtained by heating said sealed container at a temperature of from about 212°F to about 270°F.

87. A method according to Claim 86, wherein the foodstuff is blanched in a liquid at a temperature of from about 170°F to 200°F and rinsed with cold water to terminate the blanch prior to being filled into said container.

88. A method according to Claim 52, 55, 57, or 61 in which commercial sterilization is effected by heating at a temperature in the range of from about 220°F to about 260°F.

89. A method according to Claim 86 in which the container is heated at a temperature of from about 220°F to about 260°F.

90. A hermetically sealed package containing thermally processed seafood selected from the group consisting of sardines and salmon and a mixture consisting essentially of an aldonic acid and its lactones or a precursor thereof in water in amount adequate to have maintained the texture of the seafood during the thermal processing with improvement of the seafood flavor and/or odor and/or color as compared to the same package obtained without the aldonic acid and its lactones.

91. The package according to Claim 90 in which the amount of aldonic acid and its lactones or a precursor thereof is from about 0.2 to less than about 1.1 percent by weight based upon the weight of the seafood.

92. The package according to Claim 90 in which the aldonic acid is gluconic acid and its lactones are glucono- delta lactone and glucono-gamma lactone.

93. The package according to Claim 90, wherein the seafood is sardines.

94. The package according to Claim 90, wherein the seafood is salmon.

95. A method of thermally processing seafood selected from the group consisting of sardines and salmon which comprises combining the seafood with an aldonic lactone prior to thermal processing, hermetically sealing a container with the combination therein, and thermally processing the combination in the sealed container, wherein the aldonic lactone is hydrolyzed to a mixture of aldonic acid and its lactones, the mixture being effective to maintain the texture of the seafood and/or to improve the flavor and/or odor and/or color of the seafood as compared to the same seafood processed without the aldonic acid and its lactones.

96. The method according to Claim 95 in which the amount of aldonic acid and its lactones is from about 0.2 to less than about l.l percent by weight, based upon the weight of the seafood.

97. The method of Claim 95, wherein the seafood is sardines.

98. The method of Claim 95, wherein the seafood is salmon.

99. The method according to Claim 95 in which the aldonic acid is gluconic acid.

100. A method of maintaining the texture of freshly harvested seafood selected from the group consisting of sardines and salmon during thermal processing which comprises, combining in a container the freshly harvested seafood with a mixture consisting essentially of an aldonic acid and its lactones or a precursor thereof in an amount sufficient to maintain the texture of the seafood through thermal processing, hermetically sealing the container, and thermally processing the seafood in the presence of the aldonic acid and its lactones, whereby the flavor and/or odor and/or color of the seafood are improved as compared to the same seafood thermally processed without the aldonic acid and its lactones.

101. The method of Claim 100, wherein the amount of the mixture of aldonic acid and its lactones is from about 0.2 to less than about 1.1 percent by weight based upon the weight of the seafood.

102. The method according to Claim 95 or 100, wherein the seafood is combined with glucono-delta lactone.

103. A hermetically sealed package according to Claim 90 in which the package is a metal container.

104. A method according to Claim 95 in which the seafood is blanched in a liquid and rinsed with water to terminate the blanch prior to being filled into said container.

105. A method according to Claim 100 in which the seafood is blanched in liquid prior to being filled into said container.

106. A method according to Claim 95 or 100, wherein the seafood is combined with glucono-delta lactone in admixture with its hydrolysis products.

107. A method according to Claim 106, wherein the glucono- delta lactone is present as an equilibrim mixture of gluconic acid, glucono-delta lactone, and glucono-gamma lactone.

108. A method of thermally processing a plastic food container having a foodstuff therein, which comprises combining the foodstuff with an acidulant consisting essentially of a mixture of an acid and its lactones or a precursor of said mixture in an amount sufficient to reduce its equilibrium pH without any degradation of the organoleptic properties of said foodstuff as a result of the combination with said acidulant, hermetically sealing the container, and thermally processing the foodstuff in the container.

109. The method of claim 108, wherein the acidulant is glucono-delta lactone.

110. The method of claim 108, wherein the thermal processing parameter is carried out at a temperature sufficient to achieve a container center temperature of 205°F.

111. The method of claim 110, wherein the acidulant is glucono-delta lactone,

112. The method of Claim 108, wherein the temperature is below about 240°F.

113. The method of claim 108, wherein the temperature is from about 212°F to about 240°F.

114. The method of claim 109, wherein the temperature is from about 212°F to about 240°F.

115. The method of claim 108, wherein the foodstuff is an acid foodstuff.

116. The method of claim 108, wherein the foodstuff is a low acid foodstuff.

117. The method of claim 109, wherein the foodstuff is a low acid foodstuff.

118. The method of claim 108, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, beans, and corn.

119. The method of claim 109, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, beans, and corn.

120. The method of claim 110, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, beans, and corn.

121. The method of claim 111, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, beans, and corn.

122. The method of claim 112, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, beans, and corn.

123. The method of claim 113, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, beans, and corn.

124. The method of claim 114, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, beans, and corn.

125. The method of claim 111, 112, 113, or 114, wherein prior to the combining step the foodstuff is low acid.

126. The method of claim 108, 109, 112, 113 or 114, wherein the plastic container is comprised of a polyolefin.

127. The method of claim 126, wherein the plastic container is rigid and has a top closure comprised of a material selected from the group consisting of metal, plastic, and a combination of metal and plastic.

128. A method for substantially reducing the time and/or temperature to which a plastic container is subjected during thermal processing of_^ a foodstuff hermetically sealed therein, which comprises combining the foodstuff with an acidulant consisting essentially of a mixture of an acid and its lactones or a precursor of said mixture in an amount

ET sufficient to reduce its equilibrium pH to 4.6 or below, hermetically sealing the container with the acidulated foodstuff therein, and thermally processing the container at a time and/or temperature which is reduced and which thereby reduce softening and distortion of the plastic container during the thermal process, relative to the time/temperature which would have been employed and the consequent increased softening and distortion of the plastic container which would have occurred if the foodstuff were not so acidulated.

129. The method of claim 128, wherein the acidulant is glucono-delta lactone.

130. The method of claim 128, wherein the thermal processing parameter is carried out at a temperature sufficient to achieve a container center temperature of 205°F.

131. The method of claim 130, wherein the acidulant is glucono-delta lactone.

132. The method of claim 128, wherein the temperature is below about 240°F.

133. The method of claim 128, wherein the temperature is from about 212°F to about 240°F.

134. The method of claim 129, wherein the temperature is from about 212°F to about 240°F.

135. The method of claim 128, wherein the foodstuff is an acid foodstuff.

136. The method of claim 128, wherein the foodstuff is a low acid foodstuff.

137. The method of claim 129, wherein the foodstuff is a low acid foodstuff.

138. The method of claim 128, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

139. The method of claim 129, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

140. The method of claim 130, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish meat, meat products, and beans.

141. The method of claim 131, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

142. The method of claim 132, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

143. The method of claim 133, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

144. The method of claim 134, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

145. The method of claim 131, 132, 133, or 134, wherein prior to the combining step the foodstuff is low acid.

146. The method of claim 108, 109, 112, 113, or 114, wherein the plastic container is comprised of a polyolefin.

147. The method of claim 126, wherein the plastic container is rigid and has a top closure comprised of a material selected from the group consisting of metal, plastic, and a combination of metal and plastic.

148. A method for substantially reducing the softening and distortion of a plastic container during thermal processing of a foodstuff hermetically sealed therein, which comprises combining the foodstuff with an acidulant consisting essentially of a mixture of an acid and its lactones or a precursor of said mixture in an amount sufficient to reduce its equilibrium pH to 4.6 or below, and thermally processing the foodstuff in the container at a time/temperature parameter substantially lower than possible if said equilibrium pH were above 4.6 during said thermal processing, said reduced time/temperature parameter being responsible for reducing the side and bottom wall distortion of said container.

149. The method of claim 148, wherein the acidulant is glucono-delta lactone.

150. The method of claim 148, wherein the thermal processing parameter is carried out at a temperature sufficient to achieve a container center temperature of 205°F.

151. The method of claim 150, wherein the acidulant is glucono-delta lactone.

152. The method of claim 148, wherein the temperature is below about 240°F.

153. The method of claim 148, wherein the temperature is from about 212°F to about 240°F.

154. The method of claim 149, wherein the temperature is from about 212°F to about 240°F.

155. The method of claim 148, wherein the foodstuff is an acid foodstuff.

156. The method of claim 148, wherein the foodstuff is a low acid foodstuff.

157. The method of claim 149, wherein the foodstuff is a low acid foodstuff.

158. The method of claim 148, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

159. The method of claim 149, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

160. The method of claim 150, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

161. The method of claim 151, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

162. The method of claim 152, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

163. The method of claim 154, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

164. The method of claim 154, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

165. The method of claim 151, 152, 153, or 154, wherein prior to the combining step the foodstuff is low acid.

166. The method of claim 148, 149, 152, 153, or 154, wherein the plastic container is comprised of a polyolefin.

167. The method of claim 156, wherein the plastic container is rigid and has a top closure comprised of a material selected from the group consisting of metal, plastic, and a combination of metal and plastic.

168. A hermetically sealed plastic container containing an acid foodstuff of commercial sterility and an acidulant consisting essentially of a mixture of an acid and its lactones or a precursor of said mixture which imparts to the foodstuff an equilibrium pH below what it was prior to its having been combined with the acidulant, the foodstuff having an improved organoleptic quality as compared to the organoleptic quality which the commercially sterile foodstuff would have had, had it not been combined with the acidulant.

169. The plastic container of claim 168, wherein the container is rigid and is sealed with a top closure comprised of a material selected from the group consisting of metal, plastic, and a combination thereof.

170. The plastic container of claim 168, wherein the container is comprised of a polyolefin.

171. The plastic container of claim 169, wherein the container is comprised of a polyolefin.

172. The plastic container of claim 168, 169, _70, or 171, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and corn.

173. The plastic container of claim 168, 169, 170, or 171, wherein the acidulant is glucono-delta lactone.

174. The plastic container of claim 172, wherein the acidulant is glucono-delta lactone.

175. The plastic container of claim 169, wherein the container has multiple layers and an internal layer is an oxygen barrier layer.

176. The plastic container of claim 170, wherein the container has multiple layers and an internal layer is an oxygen carrier layer.

177. The plastic container of claim 171, wherein the container has multiple layers and an internal layer is an oxygen barrier layer.

178. A method of thermally processing a foodstuff in a rigid plastic container with minimal plastic softening and distortion during thermal processing, which comprises: filling the container with foodstuff an acidulant and its lactones or a precursor thereof in an amount to lower the equilibrium pH to 4.6 or less; hermetically sealing the container and subjecting the sealed contents to a time-temperature of said parameter being sufficient to commercially sterilize the contents; the temperature of said parameter being lower than the higher temperature commercial sterilizing parameter needed when the acidulant is not present, the lowered temperature parameter being primarily responsible for the reduced softening and distortion compared to the higher parameter.

179. The method of claim 178, wherein the acidulant is glucono-delta lactone.

180. The method of claim 178, wherein the thermal processing parameter is carried out at a temperature sufficient to achieve a container center temperature of 205°F.

181. The method of claim 180, wherein the acidulant is glucono-delta lactone.

182. The method of claim 178, wherein the temperature is below about 240°F.

183. The method of claim 178, wherein the temperature is from about 212°F to about 240°F.

184. The method of claim 179, wherein the temperature is from about 212°F to about 240°F.

185. The method of claim 178, wherein the foodstuff is an acid foodstuff.

186. The method of claim 178, wherein the foodstuff is a low acid foodstuff.

187. The method of claim 179, wherein the foodstuff is a low acid foodstuff.

188. The method of claim 179, wherein the foodstuff is

SUBSTITUTESHEET selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

189. The method of claim 179, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

190. The method of claim 180, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

191. The method of claim 181, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

192. The method of claim 182, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

193. The method of claim 183, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

194. The method of claim 184, wherein the foodstuff is selected from the group consisting of lasagna, ravioli, spaghetti, chili, fish, meat, meat products, and beans.

195. The method of claim 181, 182, 183, or 184, wherein prior to the combining step the foodstuff is low acid.

196. The method of claim 182, 183, or 184, wherein the plastic container is comprised of a polyolefin.

197. The method of claim 186, wherein the plastic container is rigid and has a top closure comprised of a material selected from the group consisting of metal, plastic, and a combination of metal and plastic.

198. An improved method of processing a plastic container having a foodstuff hermetically sealed therein, which foodstuff is subjected to a time and temperature parameter for commercial sterilization, which parameter causes softening and distortion of the plastic container, comprising the steps of combining the foodstuff with an acidulant consisting essentially of a mixture of an acid and its lactone(s) or a precursor of said mixture in an amount sufficient to reduce the equilibrium pH of said foodstuff

SUBSTITUTESHEET without any degradation of the organoleptic qualities of said foodstuff attributable to the use of said acid and its lactone(s) relative to the use of an acid alone, hermetically sealing the container with the acidulated foodstuff therein, and thermally processing the container with a time and temperature parameter which is reduced and which thereby reduces softening and distortion of the plastic container during the thermal process, relative to the time and temperature parameter which would have normally been employed with said foodstuff and the consequent increased softening and distortion of the plastic container which would have occurred if the foodstuff were not so acidulated.

199. The method of claim 108, wherein the foodstuff is selected from the group consisting of corn, peas, and green beans and mixtures thereof.

200. The method of claim 108, wherein &he foodstuff is selected from the group consisting of tomatoes and blueberries.

201. The method of claim 108, wherein the equilibrium pH of the foodstuff is reduced to 4.0 or less.

202. The method of claim 108, wherein the equilibrium pH of the foodstuff is reduced to from about 4.7 to 5.6.

203. The method of claim 135, wherein the acid foodstuff is selected from the group consisting of tomatoes and blueberries.

204. The method of claim 127, 135- or 203, wherein the equilibrium pH of the foodstu f is reduced to 4.0 or less.

205. The method of claim 155, wherein the acid foodstuff is selected from the group consisting of tomatoes and blueberries.

206. The method of claim 148, 155, or 205, wherein the equilibrium pH of the foodstuff is reduced to 4.0 or less.

207. The plastic container of claim 168, wherein the foodstuff is selected from the group consisting of corn, peas, and green beans and mixtures thereof.

208. The plastic container of claim 168, wherein the foodstuff is selected from the group consisting of tomatoes

SUBSTITUTESHEET and blueberries.

209. The method of claim 185, wherein the acid foodstuff is selected from the group consisting of tomatoes and blueberries.

210. The method of claim 178, 185, or 209, wherein the equilibrium pH of the foodstuff is reduced to 4.0 or less.