NO142332B - PROCEDURE FOR MANUFACTURING A FOOD PRODUCT - Google Patents

Description

The present invention relates to a heat-stable or sterilizable food product comprising solid foodstuffs in an aqueous phase with a pK value in the range 5-, 5 and thickened or gelled by a thermo-reversible or heat-stable gel structure. More specifically, the invention concerns a method for producing such a product.

In the food industry, a number of gelling, binding

and thickeners, including seaweed extracts, gelatin, modified starches, caseinates, egg whites and galactomannan gums, for the manufacture of such products as meat pudding, tinned ham and pet sheep. However, these materials have the disadvantage that they are extracted from raw materials that are not easily available,

and in many cases the annual supply depends on the weather and wind. In addition, the materials are often expensive, partly as a result of the complicated cleaning process used in their manufacture.

In contrast, raw material sources for pectin are found in

abundance, as substances containing pectin are found in the tissues of all green land plants and are currently extracted from a number of waste products, e.g. flesh and peel from citrus fruits and apple press residues.

In particular, citrus peel and similar sources containing protopectin are available in very large quantities. E.g. in 1972-73 the state of Florida in the USA alone produced approximately 600,000 tons of dried citrus waste, most of which is used as animal feed. Citrus waste results from the extraction of fruit juice from oranges, lemons and other citrus fruits, and consists of the peel and the white of the fruit, which comprises approx. 40-60% of the whole fruit.

Although a small part of the shell is dried and used for the production of high and low methoxyl pectins, the majority is used as animal feed, as no other use has been found for the material. Orange peel in particular causes problems for pectin producers, as it is difficult to filter and contains large amounts of enzymes that attack the pectin molecule.

For approx. 30 years ago, US-PS 2,132,065 described a method for the production of a raw, alkaline, screened pectate mass, but this product does not seem to have found a significant market and is not currently being produced.

Pectin substances are complex, colloidal carbohydrate derivatives

which occur in and are produced from plants. They consist mainly of polymers of o<-D-galacturonic acid, although small amounts of neutral sugars, e.g. rhamnose, xyose and gulose can occur in the main chain of the polygalacturonic acid or as side chains. The carboxyl groups of the polymers can be esterified with methyl groups to a greater or lesser extent, and unesterified groups can be completely or partially neutralized with one or more bases. The water-insoluble pectin substance that occurs in plants is known as protopectin and on limited hydrolysis yields pectin acids that contain a significant proportion of methyl ester groups, and pectins, which are the water-soluble pectin acids that are able to form gels with sugar and acid under suitable conditions. Pectinic acid is the term used for colloidal polygalacturonic acids which are mainly free of methyl ester groups and are formed by mainly complete hydrolysis of other pectin substances.

The gelling abilities of the pectin substances depend to a decisive extent

of the proportion of galacturonic acid residues that are methoxylated. In a fully esterified substance that is esterified with methyl groups, i.e.

has a degree of esterification (D.E.) of 100%, the content of methoxyl is approx. 15 percent by weight. Pectins that are currently commercially available,

and which are used for gelling purposes, can be divided into two classes:

1. High-methoxy pectins that have an esterification degree of over 50% form gels of the traditional jam type. Pectins off

• this type will only form gels at pH values below 3.5 and in the presence of substances which are believed to cause dehydration of the pectin molecule. For this purpose, sugar levels above 60% are usually used, although materials such as alcohol and glycerol can be used. High-methoxy pectins are primarily used as

gelling agents in preserves and confectionery or confectionery.

2. So-called low-methoxy pectins where usually between 20 and 40%

of the galacturonic acid residues are esterified. Pectins of this type can form gels over a wider range of pH values in the absence of sugar, but require the presence of divalent alkaline earth ions. They have the greatest stability in the pH range 4.0-4.5, especially when the pectin gel is subjected to heat treatment (see GB-PS 814 549).

Low-methoxyl pectins have been used as gelling agents

in food products such as jam for diabetics and fruit milk desserts. Commercially available low-methoxy pectins are usually produced from high-methoxy pectins, either by treatment with acids over a very long period or by the action of ammonia in alcohol systems. In the latter case, the resulting pectin product will contain some galacturonic acid residues where the carboxyl groups have been amidified.

In certain cases, it is desirable at approximately neutral pH values to form gelled or thickened food products which have then been exposed to heat treatment to achieve pasteurization or sterilization. The desired consistency of the gel can range from firm, rigid gel to a viscous sauce. Such products will generally consist mainly of meat or fish, but may also consist

of vegetables or other foodstuffs. It has been found that it is not possible to form satisfactorily thickened or gelled canned products under such conditions of heat treatment and pH value, when either high-methoxyl pectins or pectins containing methoxyl in the range of 20-40% are used. It is believed that one of the reasons for this is that pectins of these types depolymerize at high temperatures and neutral pH values and thereby lose their gel-forming properties.

It has now been found that if a natural pectin source material is used with a degree of esterification (proportion of the carboxyl groups that are methylated) of less than 20% or an isolated pectate with a degree of esterification of less than 10%, the molecule seems to have sufficient heat stability to retain its gelling or thickening properties in products with neutral or nearly neutral pH values after heat treatment. Such pectin materials can therefore be used as gelling, thickening or binding agents in pasteurized, sterilized, canned or otherwise heat-treated food products.

For the sake of simplicity, pectin materials which have a degree of esterification as mentioned/hereafter will be referred to as pectates, this term including not only the ideal case where essentially no methoxyl groups are present, but also pectins with a degree of esterification of up to 20% , respectively 10%. The preparation of pectates by cold, alkaline hydrolysis of protopectin is described in US-PS 2,132,065.

The method according to the invention thus involves the gel structure being formed by reacting a non-toxic di- or trivalent metal ion in the aqueous phase with an isolated pectate with an esterification degree of less than 10% or with a natural pectin source material with a pectin content of at least 5% by weight, calculated on dry weight, and defatted to a degree of esterification of less than 20%. The invention has particular value for the production of thickening or gelation of nearly neutral meat-containing products

ducts, more specifically in the pH value range 5-8.5, and more particularly 6.0-7.5. Such compositions are usually heat pasteurized or sterilized and can be contained in hermetic packages, e.g. boxer. They may exhibit the firmness characteristic of a gel, or the viscosity and usually the pseudoplastic or thixotropic properties required of thickened products, as described below.

The pectin substances useful for the present invention include not only purified or isolated pectates with a degree of esterification of less than 10%, but also raw natural pectin sources, e.g. apple, citrus fruit or sugar beet residues, which have, if necessary, been subjected to culling, e.g. by alkalis or enzymes to reduce their degree of esterification to below 20%. Usually, natural pectin substances must be intentionally removed, e.g. by alkaline hydrolysis or by means of an enzyme, e.g. pectinesterase. However, intentional esterification need not be necessary, if a natural protopectin source with a degree of esterification of less than 20% is used, e.g. because the source contains pectinesterase. Furthermore, if the source contains such an enzyme, simply softening the source material or adding it to a substantially neutral food mixture prior to pasteurization or sterilization may cause a reduction in the degree of esterification sufficient for the purposes of the present invention.

If orange peel is ground to a small particle size, preferably neutralized to a pH value of 7-8 with an alkali, e.g. :sodium carbonate, for a period of e.g. 30 minutes, washed to remove sugars and unwanted soluble components and dried, the milled product can thus be used as a thickening

and gelling agent in canned foods. Since most of the components that give the orange's aroma and color are in the outer

made from the shell ("flavedo"), it is desirable, when the treated shell is used for thickening or gelling products such as meat or fish, that this flavedo is removed before processing, so that the less characteristically tasting albedo remains. Cut-off techniques for removing the flavedo from the orange peel from the pressed orange halves are well described in the literature.

The reaction mechanism by which the protopectin in the shell is transformed into a gelling agent is not fully understood. Although the invention depends on some theory for its execution, a possible explanation is that the enzymes released during the grinding of the orange peel, at least partially de-methoxylate the pectin molecule which is believed to be bound to hemicelluloses and other materials in protopectin -configuration, and that further de-methoxylation and solubilization of the pectin occurs during subsequent heat treatment in the essentially neutral food product. It is believed that the resulting pectate so

reacts with alkaline earth ions in the food product to form a thickened or gelled system.

It will be understood that any hydrolysis or other treatment of the pectin substance should not result in too strong a reduction of its molecular weight, as this impairs its properties with regard to gelation and thickening. It is believed that if the deesterification is carried out with an enzyme, the results which are characteristic of the present invention can be obtained with a higher degree of esterification than if the deesterification is carried out by other means, presumably as a result of the sequential nature of this type hydrolysis in contrast to the random removal of methoxyl groups along the chain when acid or alkaline hydrolysis is used. This is particularly noticeable with stronger heat treatments, e.g. by retort processing of canned products, and it can be assumed that the degree of depolymerization of the pectate under these conditions is less than in the case of enzyme-removed material.

The determination of the degree of esterification can be carried out by measuring the methoxyl content in the material and measuring the material's content of galacturonic acid. Although a modification of Hinton's saponification procedure is commonly used when measuring the methoxyl content of high-methoxyl pectins, it has been found that this technique can give inaccurate results when the samples being examined are crude protopectin sources, presumably as a result of reaction with other components of the source material, e.g. protein.

Both the modified saponification method and a more special method based on gas/solid chromatography along the lines proposed by Krop et al. (Lebensm. - Wiss. u. Technol., volume 7, 1974, no. 1), has been used. Both methods have given similar results for crude protopectin sources with low methoxysulfur content, i.e.

the preferred material according to the invention.

Modified saponification method:

A sufficient sample of finely ground, dried material (usually

2 g) to release no more than 0.02 g of methanol is stirred with 250 ml of water and

is heated on a boiling water bath for 20 minutes with occasional stirring, after which the mixture is softened with a high-speed blender. The dispersion is cooled to 20°C and neutralized to a pH value of 8.4 using a pH electrode to sense the breakpoint and N/10 sodium hydroxide to effect the neutralization. 20.00 ml of N/10 NaOH is then added, and after stirring the mixture is allowed to stand for 20 minutes. 20.00 ml N/10 HCl is added, and the excess HCl is determined by titration with N/10 sodium hydroxide solution to a pH cut-off point of 8.4, using a pH electrode to detect the cut-off point. Titration liquid = B ml. Gas/solid chromatography; 2 g of finely ground dried material is stirred with 100 ml of water and heated on a boiling water bath for 20 minutes with occasional stirring, after which the mixture is soaked in a rapid mixer. The dispersion is cooled to 20°C, and 20 ml of a 1N sodium hydroxide solution is added with stirring. After 20 minutes at 20°C, 5 ml of 50% concentrated hydrochloric acid are stirred in, and the mixture is diluted with distilled water to 200 ml. The dispersion is allowed to stand for 10 minutes for precipitation to occur.

The methanol content of the supernatant liquid is then determined using gas chromatography, using conditions similar to those described by Krop et al (in the cited place).

The content of galacturonic acid in the sample is measured by repetition

of the method described above up to and including the step where the mixture stands for 20 minutes with 1N sodium hydroxide after 20 ml of concentrated hydrochloric acid has been added while stirring. 800 ml of propanol-2 is added, and the dispersion is allowed to stand for 30 minutes.

The precipitated solids are filtered from a Buchner funnel and washed thoroughly with 60% by volume propanol-2 in water. The solids are then dispersed in water, 10.0 ml of 0.1N sodium hydroxide is added, and the solids are dispersed using a rapid mixer. The dispersion is titrated to a pH value of 8.0 with 0.1N sodium hydroxide using a pH meter (titration liquid = A ml).

Pectates are usually obtained as the alkali metal salt, and it is usually necessary for a salt of a di- or trivalent metal to be present in a food product together with the pectate if a satisfactory gel is to be obtained. Such metal ions need not be necessary when only a thickening reaction is required, and the addition of such an ion can be avoided when a metal ion is naturally present in the food product or in the pectin source or pectate itself. The preferred metal ion is calcium, and suitable salts for addition to the product include dicalcium phosphate dihydrate, calcium sulfate dihydrate, calcium citrate, calcium lactate and calcium chloride.

It has been found that it is desirable to incorporate a sequestering agent or a chelating agent into the product composition, particularly when a raw protopectin source is used, where the pectate exists in the form of a divalent or trivalent metal salt or the product naturally contains high levels of divalent or trivalent metal ions. Suitable sequestering agents include sodium tripolyphosphate, sodium hexametaphosphate and trisodium citrate. Such a chelating agent will serve to delay the formation of a gel, which allows easier processing of the cold mixture and filling in e.g. cans and also a faster heat penetration during the pasteurization or sterilization. When meat types are present, an alkaline chelating agent will also help to counteract the reduction of pH

the value that has been observed when divalent or trivalent salts are added to meats. This development of acidic conditions can also be counteracted by the addition of an alkali, e.g. sodium hydroxide, or an alkaline buffer.

The amount of pectate or raw denatured pectin material required to thicken a thickened or gelled food product can vary widely. When a pure pectate is used, this can be present in an amount of 0.1-10% by weight of the food product, preferably 0.5 to 2.0%. When a source of raw, screened pectin is used, the concentration of such pectin material (on a dry basis) may be in the range of 0.1-20% by weight of the food product, but preferably in the range of 0.5-3%. The source of raw, deveined pectin must contain more than 5% pectin (and preferably more than 10% pectin) calculated on dry matter.

The source of raw, defatted pectin can be used in dried form

or, e.g. when the user's location is suitably close to the process

the station, without drying, and the required quantities then depend on the content of solids in the pectin source.

According to the preferred aspect of the present invention, it has been found that decanted citrus peel is surprisingly effective for gelling and thickening. E.g. found that a meat product gelled with 1.5% by weight orange peel was firmer than similar products gelled with 1% pure pectate. This was surprising because analysis showed that the orange peel contained only 30% pectin (expressed as galacturonic acid). The orange peel can be subjected to alkaline etching, but it has been found that this is not a decisive step for achieving the object of the invention.

The dried treated shell contains approx. 20-45% pectin (expressed as galacturonic acid) depending on the type of fruit, degree of ripeness, aorta and other factors, and the remaining dry solids include hemi-celluloses, araban and other fillers. More recent nutritional thinking goes in the direction of considering such cellulose-like materials in the quantities supplied by the method according to the invention, as clearly beneficial for health. A further advantage of the use of raw materials such as treated shell according to the present invention lies in the material's low caloric value, which together with the properties described above, indicates that it can be successfully used in slimming and diabetic foods, where treated shell can be used instead of caloric water binders such as e.g. starch to achieve the necessary water-binding properties.

Although a number of foods, e.g. vegetables, fruits and

sauces, can be thickened or gelled using pectate or treated protopectin materials, these are particularly advantageous in canned meat products where the presence of the insoluble non-pectin-containing materials from the raw material, e.g. finely divided shell, is hidden by the fine meat substances obtained by the heat coagulation of soluble meat proteins.

A very useful property in certain gelled systems is thermo-reversibility. In this connection, a thermoreversible gel can be defined as a gel that has a melting point and a solidification point that lie within the temperatures relevant for the preparation and use of the gelled system.

It has been found that the melting point and solidification point of pectal gels produced according to the present invention can be adjusted by increasing or decreasing the content of available calcium or other non-toxic di- or trivalent metal ions in the food product. The availability of calcium or other metals for interaction with the pectate depends not only on the amount of calcium or other metal present, but also on the type of metal salt used and the type and amount of sequestering agent present in the system.

At high levels of available calcium there can thus

food structures are formed that are stable against heat treatment,

while at lower levels of available calcium, thermoreversible gelled or thickened systems can be obtained.

It has also been found that a thickened food product, i.e. a product in which the aqueous phase has an increased viscosity, can be produced either by direct use of relatively high levels of crude or pure pectate sources or advantageously by the use of much lower levels of the crude or pure pectate source in the presence of added calcium ions and sequestering agent. These lower levels are at such a concentration that a coherent gel structure cannot be formed, but instead viscous and usually pseudoplastic solutions are obtained.

It has also been found that if peel or gum from psyllium seeds is added to food product mixtures containing treated orange peel, an unexpected synergistic reaction occurs during the heating treatment step, as a firmer, tougher and more elastic gel structure is obtained in the finished product than is achieved with each system for themselves. Hull or gum of psyllium seeds is extracted from a group of plants of the genus Plantago and used for various pharmaceutical applications.

Although citrus peels have been found to be particularly useful for

the described application, are also other protopectin sources, e.g. apple or pear press residues or sugar beet residues useful for the purposes of the invention.

The method according to the invention can be carried out with a number of foodstuffs and under a number of conditions. For example, pectates can be used in the production of food products in sealed packages or containers, e.g. boxer. Such products include varieties of ham, meat pudding and food for pets, especially for dogs and cats, and also foods comprising a thickened aqueous medium, e.g. stews and soups. Although the pectate gel, depending on the available calcium content, may melt below the temperature used in the retort treatment of the cans, the pectate agent retains its gel-forming properties and solidifies again on cooling.

Pectates can also be used as binders to obtain a

firm consistency in prepared products such as sauces and fillings in meat pies. During preparation, such products do not reach as high a temperature as canned food products, but are at least exposed to pasteurization conditions. Pasteurization can be defined as the application of sufficient heat, usually at temperatures below 100°C, to effectively remove vegetable bacteria, while sterilization is the application of heat at temperatures above 100°C to effectively remove both vegetable bacteria and spores.

Further examples of the use of pectates as binders include the production of lost meat or shaped pieces of meat which are able to retain their integrity, e.g. when incorporated into a canned product. Such products can be prepared by

shape, e.g. extrudates, a mixture of finely divided meats or by-products of meat or vegetable protein together with the pectate material and desirable sequestering agent. The product can be post-treated in a solution of alkaline earth ions.

Pectates can also be used as binders in semi-soft foods, i.e. those that have been stabilized by incorporating sufficient water-soluble substances to reduce the water activity to between 0.65 and 0.85 and contain an antifungal agent.

The preferred composition of products manufactured according to the invention depends on the particular type of product being considered,

In the case of canned meat or meat by-products, the starting point is preferably a mixture which, on a weight basis, contains 20 - 95% meat or meat by-products, 0.1 - 5% pectate (or 0.1 - 10% finely divided citrus peel calculated on a dry basis) , 0-5% acceptable, non-toxic alkaline earth metal compound. and 0 - 5% sequestering agent and has a moisture content of 50 - 95%.

In the case of processed meat products, including sausages, which are prepared by binding together finely divided meats or meat by-products, the starting point is preferably 40 - 95% meat or meat by-products, 0.1 - 5% pectate (or 0.1 - 10% finely divided citrus peel calculated on a dry basis), 0-5% acceptable alkaline earth metal compound and 0-5% sequestering agent, the moisture content being 50-95%.

In the case of simulated pieces of meat formed from substances other than meat, e.g. vegetable proteins, preferably based on a mixture of 5 - 50% vegetable protein, 0.1 - 5% pectate

(or 0.1 - 10% finely divided citrus peel"), 0-5% acceptable alkaline earth metal compound and 0 - 5% sequestering agent, the moisture content being 50 - 95%.

The following are examples of execution of the present invention applied to a number of approximately neutral products. The examples demonstrate the stability of the gelling or thickening agent to heat treatment. All parts and percentages refer to weight, unless the context indicates otherwise.

Example 1

Use of isolated pectate:

5 grams of a commercial preparation of sodium pectate (Sodium Polypectate from Sigma Chemical Company) which had approximately 1% of remaining methoxyl groups was dissolved in 200 ml of water and added to 250 g of chopped lung pieces. A slurry of 20 g of dicalcium phosphate dihydrate (CaHPO. • 2Ho0) and 5 g of sodium tri-polyphosphate (Na^P-O^) in 50 ml of water was added with stirring to the lung/polypectate mixture, and the aqueous mixture was filled into 453 g cans, closed and sterilized for 1 hour at 13.8 N/cm 2 overpressure in a steam autoclave.

After the cans had cooled, they were opened, and the pieces of lung were found to be encased in a firm, clear, cohesive gel. The product's pH value was 6.2.

For the sake of comparison, the effect of the use of pectins with a higher methoxyl content was demonstrated by repeating this Example 1, except that the sodium pectate was replaced by an equivalent amount by weight of pure low methoxyl pectin with a degree of esterification of 35%. (Hj?. Bulmer Ltd.). The sterilized product consisted of boiled pieces of lung in a thin watery liquid and had a pH

value of 6.1.

When this example was repeated once more, using instead of sodium pectate a corresponding amount by weight of a commercial preparation of low methoxy pectin amide with a degree of esterification of 20-

33% and an amidation degree of 20-25% (produced by Cesalpinia),

the sterilized product consisted of boiled pieces of lung in a thin watery liquid and had a pH value of 6.1.

Example 2

5 g of a commercial preparation of sodium pectate (Sodium Polypectate from Sunkist Growers) which showed essentially no methoxyl groups was dissolved in 150 ml of water and added to 288 g of a mixture of meat scraps commonly used for canned dog food. A slurry of 20 g of dicalcium phosphate and 5 g of sodium tripolyphosphate in 60 ml of water was added with stirring, and the mixture was charged

cans and treated as described in example 1.

After the cans had cooled, they were opened and the product was found to be a cohesive package of offal surrounded by a clear, cohesive gel. The product's pH value was 6.2.

Example 3

Example 1 was repeated with the exception that the 20 g of dicalcium phosphate was replaced with 5 g of calcium sulfate dihydrate (CaS04•2H20).

The sterilized product had a similar appearance to that described in Example 1, although the gel was marginally softer in consistency. The product's pH value was 6.5.

Example 4

Example 1 was repeated with the exception that the level of dicalcium phosphate was reduced from 20 g to 5 g, and the 5 g of sodium tripolyphosphate was replaced by 0.25 g of sodium hydroxide.

The sterilized product consisted of pieces of lung baked into a

soft coherent jelly and had a pH value of 6.4.

Example 5

Use of fresh finely divided orange peel:

a) Treated orange peel was prepared as follows:

-5r,-2 kg navel oranges from South Africa were passed through a

scraper for removing the flavedo. The oranges were then cut in half and pressed to remove the juice. The resulting shell (3.45 kg) was pressed through a mill equipped with a 4.8 mm plate. The ground shell was washed with 2 liters of tap water and pressed into a muslin bag. 4.16 kg of the washed orange pulp was obtained. The pH value of the treated shell was 5.2.

b) Preparation of a gelled meat product:

The ingredients were mixed in a bowl, and after adding sufficient sodium carbonate (about 0.4 g) to bring the pH of the mixture to 7.5, the mixture was allowed to stand for two hours to reduce the degree of esterification of the pectin content to below 20% . The mixture was then filled into cans which were closed and sterilized at 16.5

N/cm 2 for 50 minutes. After the cans had stood overnight, they were opened and found to contain a continuous meat package, consisting of pieces of meat embedded in a firm, crisp, clear jelly. The product's pH value was 6.0.

Example 6

Uses of dried orange zest:

a) The dried mass was prepared as described in example 5

with the exception that after washing and pressing it became ground shell

dried at 60°C in a laboratory dryer with a fluidization layer. Drying proved difficult due to the adhesive nature of the ground shell, and drying took several hours. The pectin content of the dried peel had a degree of esterification of less than 20%.

b) Preparation of a gelled meat product:

The ingredients were mixed together, filled into cans, closed and

sterilized in an autoclave at 16.5 N/cm 2 for one hour. After the product had stood overnight, it was found to consist of a firm meat package containing pockets of a firm, brittle jelly. There was little or no aroma or taste of orange. The product's pH value was 5.85.

Example 7

Use of alkali-treated orange peel:

a) 11.56 kg whole oranges from California were scraped to remove the flavedo, split in half and pressed to remove the fruit/juice. The obtained 4.91 kg of husks were pressed through a grinder equipped with a 4.8 mm plate, washed with 3 kg of water and pressed. \

2.5 kg of water were added to the pressed peel, and the pH value was adjusted to 8.5 by adding 55 g of sodium ka-Ironate. The slurry was allowed to stand at room temperature for 18 hours and was then pressed into a muslin bag. The dewatered shell was then dried at 60°C in a dryer with a fluidization layer and coarsely ground. The pectin content in the treated peel was 10%. The alkali treatment was found to contribute markedly to the dewatering of the shell.

b) Preparation of a gelled meat product:

The treated shell was thoroughly mixed with caramel, dye

and water and then added a mixture of the other ingredients. After thorough mixing, the product was filled into cans, closed

and sterilized at 16.5 N/cm 2 for one hour. After the product had stood overnight, it was found to consist of a continuous solid meat package with pockets of clear, firm, brittle jelly. The product's pH value was 6.6.

Example 8

Use of alkali-treated orange peel with reduced levels of calcium and sequestering agent:

The dried alkali-treated orange peel described

in Example 7, was used in the following meat mixture recipe:

The sauce was prepared by mixing together the sauce ingredients except for the treated shell and heated to 90°C, after which the treated shell was added with vigorous stirring. After 3 minutes, the hot viscous sauce was added to the meat mixture and thoroughly mixed. The product mixture was filled into cans, closed and autoclaved at 16.5 N/cm 2 for one hour. After the product had stood overnight, its appearance was found to be the same as described in Example 7.

Example 9

Use of alkali-treated orange peel as a thickener without added calcium and without sequestering agent:

The dried alkali-treated orange peel described in Example 7 was used in the following meat mixture recipe:

The treated shell was added to the cold water containing the caramel and dye solution, and after mixing for 3 minutes, the resulting slurry was mixed with the meats and the rest of the water. The mixture was then filled into cans, sealed and autoclaved at 16.5 N/cm o for one hour. After the product had sat overnight, it was found to be a non-cohesive package consisting of bloated pieces of meat embedded in a viscous, thick, glossy sauce. The product's pH value was 6.3.

Example 10

Use of dried alkali-treated orange peel with a sequestering agent, but without added calcium ions:

The dried alkali-treated orange peel described in Example 7 was used to prepare the following meat mixture:

The ingredients in the sauce were mixed and brought to the boiling point, after which they were added to the meat mixture. After further mixing, the mixture was filled into cans, sealed and autoclaved at 16.5 N/cm o for one hour. After the product had been left overnight, it was found to contain a firm, cohesive meat package with pockets of clear, soft, brittle jelly, particularly on the surface of the package. The product's pH value was 6.5.

Example 11

Use of dried alkali-treated grapefruit peel:

Grapefruit from South Africa was split in half, pressed to remove the juice and ground in a grinder equipped with a 4.5 mm disc. The 814 g of ground husk obtained in this way was washed with water from the tap and pressed to remove excess water. 500 ml of water was added to form a slurry and the pH was changed from 4.6 to 8.5 by adding 11 g of sodium carbonate. The slurry was allowed to stand at room temperature for 18 hours and was then squeezed out of excess liquid, washed once with tap water, squeezed again and then dried at 60°C in an air dryer with a fluidization layer. The treated shell, which had a pectin content with a degree of esterification below 20%, was ground into a fine powder and used in the following meat mixture:

The treated rind was dispersed in the cold water containing the caramel and color solution, and this "sauce" was added to the other meat mixture ingredients under thorough mixing. The mixture was filled into cans, sealed and autoclaved at 16.5 N/cm for one hour. After the product had been left overnight, it was found to contain a firm, cohesive package with a surface layer of soft, brittle jelly. The product's pH value was 6.2. The product had a meat-like aroma with only faint overtones of grapefruit.

Example 12

Dried lemon peel was prepared from South African lemons on

the same way as described for grapefruit in example 11. A meat-

product prepared using dried lemon peel in the same manner as described in Example 11 was found to contain a solid, combined

hanging meat package with a surface layer of soft, fragile jelly. The product's pti value was 6.2 and it had a faint aroma of lemon.

Example 13

Use of orange peel with psyllium seed peel

Dried orange peel was prepared as described in Example 6

with the exception that a drying temperature of 90°C was used. Powdered psyllium seed husks were purchased on the open market.

These materials were used to prepare the following gelled meat product:

The various ingredients of the meat mixture were combined, and after the sauce mixture had been heated to 95°C, it was added and thoroughly mixed. The mixture was filled into cans and sterilized at 16.5 N/cm 2 for one hour. After the product had been cooled and had stood overnight, it was found to consist of a rigid package of meat encased in a firm, tough, elastic gel.

The product gel was firmer and tougher than those obtained using either psyllium seed peel or treated orange peel separately.

Example 14

a) Preparation of treated orange peel.

10 kg navel oranges from South Africa were split in half, pressed

for removing the juice and then passed through a grinder equipped with a 4.5 mm plate. The ground shell was washed with tap water, pressed and slurried in water, and sufficient sodium carbonate anhydride to raise the pH to 9.0 was added with stirring. The slurry was allowed to stand for 18 hours and was then pressed, washed, pressed and roller dried. The roller-dried flakes were ground to a fine powder. The yield was 520 g, and the degree of esterification of the pectin content was below 20%.

b) Use in shaped pieces of meat.

The sodium tripolyphosphate, the dye and the caramel were dissolved

in the water, which was heated to the boiling point. Treated shell prepared as under a) above was added with vigorous stirring and the mixture was thoroughly mixed with the non-fibrous flesh. The mixture was extruded into spherical pieces into a 10% calcium chloride solution and allowed to stand for 4 hours.

The solid pieces were then removed, washed in water and autoclaved in cans at 16.5 N/cm 2 for one hour in the presence of ground meat.

After the contents of the cans had cooled, they were examined,

and the shaped pieces of meat were found to have a firmness and internal consistency similar to lungs.

Example 15

Use in imitation cuts of meat.

Caramel, color solution, sodium tripolyphosphate and treated shell (prepared as described in Example 14) were heated in the water to the boiling point, and the denatured wheat gluten was added with vigorous stirring.

The mixture was poured into a trough and allowed to cool. After standing for 1 hour, the solidified mass was cut into 19 mm pieces and treated with a gelling agent solution in cans at 16.5

2

N/cm for one hour.

The imitation pieces of meat were found, after cooling, to have retained their shape and to have a firm but rather fragile consistency, similar to boiled kidneys.

This example demonstrates the utility of treated shell for binding together denatured protein materials that have no binding properties into a cohesive mass.

Example 16

Use in fish/meat pudding products

a) Whole Spanish Valencia oranges were scraped to remove flavedoed, split in half and pressed to remove the fruit juice. In kg

of the albedo was passed through a mill fitted with a 4 mm plate and mixed with 12 g of sodium carbonate anhydride for 30 minutes. Albedoe was pressed into a muslin bag and then mixed for 5 minutes with its own weight of water. The mixture was then pressed again into a rr.usselin bag, and after grinding through a 2 mm plate, the albedo was dried on a roller dryer operating at a pressure of 54 N/cm 2. It was observed that the roller dried material had a very milder

aroma and was less yellow in color than the material dried in hot air. The material had a degree of esterification of 10%.

b) The treated husk was then used as an alternative gelling agent in comparison with a grain-based binder i

a fish/meat pudding product.

In both cases, the ingredients were mixed together, heated to boiling and held at boiling temperature for 5 minutes. The mixture was filled into cans which were sealed and sterilized in an autoclave.

After the cans had cooled, they were opened and the products compared. The product composition comprising treated husks was found to be a cohesive meat pudding package with similar firmness to the package comprising grain product, but with improved aroma and appearance.

Example 17

This example is intended to demonstrate the relationship between the degree of esterification of treated shell samples and their ability to provide thickened sauces after heat sterilization. Three samples of treated orange peel were prepared as described in example 16, except that in the first, second and third samples respectively 0.10 and 15g of sodium carbonate were added to the albedo after comminution.

The degree of esterification of the three samples was determined as described above, and the following results were obtained:

Product preparation

Oven-baked, shaped slices of meat were prepared from meat waste and binders in accordance with compositions and methods commonly used in the food industry. Three sauces were prepared using three treated shell samples by heating to the boiling point of the ingredients in the following composition:

45 parts by weight of the shaped meat slices and 55 parts by weight of the appropriate sauce were mixed together, filled into cans, sealed and sterilized in an autoclave. After cooling and opening the cans, the products were examined subjectively, and objective viscosity measurements were also carried out on the product sauces.

Example 18

Use in gelled meat products

The three samples of treated orange peel described in Example 17 were used to compare their properties in the preparation of gelled meat products.

The sauce ingredients were mixed together and heated to boiling point. The appropriate amount was then mixed with the other ingredients and the mixture filled into cans, sealed and sterilized in an autoclave. After the cans had cooled, they were opened and the appearance of the contents noted:

Sample Product appearance

1 Very soft package that collapsed when taken out of the box and consisted of pieces of meat in a thin, water-like sauce. 2 Firm, cohesive pack with a clear, glossy, firm gel. 3 Similar to sample 2 with the exception that the gel was somewhat firmer.

Example 19

Use in sausages

Beef sausages were prepared using conventional casing components and also with this component prepared with a solution of treated shell (sample 2 in Example 17) and sodium tripolyphosphate according to the composition indicated below:

To prepare the sausages, in the standard example, the beef side pieces were coarsely ground before chopping in a bowl together with water and kneading into a coarse paste. In the example with treated shell, the treated shell and the sodium tripolyphosphate were heated in the water to the boiling point and then cooled to room temperature before grinding in the bowl together with the meat to a coarse paste. The mixtures were

stuffed in a sausage skin and tying done.

After frying in fat at the same temperature and for the same time, it was found that the sausages with treated skin were firmer, juicier and had more meat aroma than the standard sausages with casing.

Example 20

Use in semi-moist compositions for dog night

The ingredients from the "A" mixture were mixed together and up-

heated to the boiling point. After boiling for 10 minutes, the weight of the mixture was adjusted to the original weight by the addition of boiling water, and the mixed ingredients from the "B" mixture were added with vigorous stirring. The whole mixture was then placed in a trough where it was allowed to cool, and was sliced and sealed in plastic bags.

The product had a pH value of 6.5 and a firm chewable consistency and a pleasant meat aroma without the usual unpleasant soy aroma and taste that occurs when soy particles and soy flour are used in conventional products to achieve the binding effect.

Claims (7)

1. Process for the production of a heat-stable or sterilizable food product comprising solid foodstuffs in an aqueous phase with a pH value in the range 5-8.5 and thickened or gelled by a thermo-reversible or heat-stable gel structure, characterized in that the gel structure is formed by a non-toxic di- or trivalent metal ion is reacted in the aqueous phase with an isolated pectate with a degree of esterification of less than 10% or with a natural pectin source material with a pectin content of at least 5% by weight, calculated on dry weight, and screened to a degree of esterification of less than 20%. 2. Method as stated in claim 1, characterized in that the natural pectin source material is finely ground before introduction and treated with alkali to reduce the degree of esterification to below 20%, the flavedo preferably being removed when citrus peel is used. 3. Method as stated in claim 1 or 2, characterized in that psyllium seed husk or gum is also added to the aqueous phase. 4. Method as stated in claim 1, characterized in that a mixture is produced which comprises 20-95% by weight of meat or meat by-products, 0.1-5% pectate or 0.1-10% finely divided citrus peel (on a dry basis), 0- 5% non-toxic alkaline earth compounds and 0-5% sequestering agent and has a moisture content of 50-95%, and that the mixture is placed in a box in a known manner. 5. Method as stated in claim 1, characterized in that a mixture is produced which comprises<p>i-40-95 weight percent meat or meat by-products, 0.1-5% pectate or 0.1-10% finely divided citrus peel (on dry base), 0-5% non-toxic alkaline earth metal compound and 0-5% sequestering agent and has a moisture content of 50-95%, and that the mixture is formed into coherent, shaped pieces with the formation of a heat-stable gel. 6. Method as stated in claim 1, characterized in that a mixture is prepared which comprises 5-50% vegetable protein, 0.1-5% pectate or 0.1-10% finely divided citrus peel, 0-5% non-toxic alkaline earth metal compound and 0 -5% sequestering agent and has a moisture content of 50-95%, and that the mixture is formed into pieces with the formation of a heat-stable gel. 7. Method as stated in claim 1, characterized in that water-soluble substances are incorporated in the product in sufficient quantity to reduce the water activity to between 0.65 and 0.85/ and that an antifungal agent is also incorporated.