Classifications

• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
  • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
  • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
  • A23L3/34—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals
  • A23L3/3454—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by treatment with chemicals in the form of liquids or solids
  • A23L3/3463—Organic compounds; Microorganisms; Enzymes
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B4/00—General methods for preserving meat, sausages, fish or fish products
  • A23B4/005—Preserving by heating
  • A23B4/0053—Preserving by heating with gas or liquids, with or without shaping, e.g. in form of powder, granules or flakes
  • A23B4/0056—Preserving by heating with gas or liquids, with or without shaping, e.g. in form of powder, granules or flakes with packages, or with shaping in the form of blocks or portions
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B4/00—General methods for preserving meat, sausages, fish or fish products
  • A23B4/12—Preserving with acids; Acid fermentation
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B4/00—General methods for preserving meat, sausages, fish or fish products
  • A23B4/14—Preserving with chemicals not covered by groups A23B4/02 or A23B4/12
  • A23B4/18—Preserving with chemicals not covered by groups A23B4/02 or A23B4/12 in the form of liquids or solids
  • A23B4/20—Organic compounds; Microorganisms; Enzymes
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/005—Preserving by heating
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/005—Preserving by heating
  • A23B7/0053—Preserving by heating by direct or indirect contact with heating gases or liquids
  • A23B7/0056—Preserving by heating by direct or indirect contact with heating gases or liquids with packages
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B7/00—Preservation or chemical ripening of fruit or vegetables
  • A23B7/10—Preserving with acids; Acid fermentation
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
  • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
  • A23L3/10—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by heating materials in packages which are not progressively transported through the apparatus
• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
  • A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
  • A23L3/16—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by heating loose unpacked materials

Definitions

• 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.
• 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.
• Clostridium botulinum 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
• 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.
• Food preservation techniques should retain the nutritional value and prolong the stability of the foods* * organoleptic properties.
• 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.
• 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 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.
• 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.
• salt 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.
• 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.
• 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 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.
• Low-acid foodstuffs 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.
• r j acid 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.
• 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 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.
• 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.
• acids such as for example, acetic, citric, lactic, malic, phosphoric and tartaric
• 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.
• 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.
• 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.
• an aldonic acid preferably gluconic acid
• Still another object of the invention is to provide commercially sterilized shrimp which has a clean shrimp flavor and odor.
• an aldonic acid preferably gluconic acid
• 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.
• GDL glucono-delta lactone
• 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.
• 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.
• 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.
• 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) .
• aldoses talose, galactose, idose, gulose, mannose, glucose, altrose and allose.
• Sugars having five carbon atoms are lyxose, xylose, arabinose and ribose.
• 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.
• 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.
• GDL glucono-delta lactone
• 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.
• lactones or other aldonic acids e.g., galactono-delta lactone.
• rapid hydrolysis through heating is preferred to help acidify the particulate foodstuff rapidly and thoroughly.
• salts which can be used in combination with certain strong acids 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.
• 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.
• 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.
• 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.
• 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:
• 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.
• 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:
• sample cans were opened and evaluated for texture, flavor, and color of the blueberries.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• GD 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.
• an organic acidulant such as citric or lactic acid
• salt NaCl
• 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.
• 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 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.
• 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.
• 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:
• CCT sterilizing value
• 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.
• 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.
• CCT can or container center temperature
• 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.
• 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.
• 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.
• 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.
• tomatoes and blueberries 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.
• 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.
• an acidulant such as citric acid
• 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.
• Steam retorting is the preferred means of thermal processing low acid foods in accordance with this invention although any suitable means may be employed.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• Plastic containers are desirable because they provide advantages of low cost, light weight, lack of rust and corrosion problems, and ease o disposability.
• 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.
• 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.
• the total internal pressure within the container during thermal processing is the sum total of all of the aforementioned pressures.
• 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.
• 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.
• SUBSTITUTE SHEET this reduces heating efficiency of the steam and can alter heat transfer within the retort.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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
• 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.
• 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.
• 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.
• 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.
• a method 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.
• 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
• 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.
• GDL glucono-delta lactone
• 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;
• FIG. 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 6 corn, and Figure 7 lasagna are 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 6 corn, and Figure 7 lasagna are representative parameter curves for
• 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.
• 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.
• 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
• 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.
• 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.
• 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.
• 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.
• squash, zucchini, melons, artichokes, cauliflower and celery are very heat sensitive.
• the equilibrium pH of a low acid foodstuff such as carrots, rice, zucchini, and the like is advantageously lowered to 4.6 or
• 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.
• a brine aqueous solution
• 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.
• 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.
• GDL 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.
• GDL acid/lactone acidulant
• 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.
• 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.
• 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.
• FIG. 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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 poly
• EVOH ethylenevinyl alcohol copolymer
• 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.
• GDL when GDL is hydrolyzed, it forms an equilibrium mixture of gluconic acid, glucono-delta lactone and glucono- gamma lactone.
• 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.
• CCT can center temperature
• 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.
• 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.
• 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.
• 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.
• 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 F 0 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.
• CCT can center temperature
• 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.
• 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.
• the temperature/time parameters of each curve to the right in the Figures are based upon a particular sterilizing value (F 0 ) for the particular product which value here is basically a time equivalent calculated at 250°F.
• F 0 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 F 0 values are derived by those skilled in the art. The higher the F 0 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.
• a sterilizing value here, for example, CCT
• CCT sterilizing value
• 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.
• CCT can or container center temperature
• 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 F 0 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 F 0 of .01.
• 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 F 0 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 F 0 of .01.
• 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 F 0 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 F 0 of .01.
• 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.
• Steritort agitated retort
• 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 F 0 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.
• 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 F 0 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 F 0 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.
• 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.
• 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) .
• 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.
• 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) .
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• Example 9 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.
• 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.
• 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.
• 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.

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• 1986
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