EP1196048A1

EP1196048A1 - Edible animal muscle protein gels

Info

Publication number: EP1196048A1
Application number: EP00947173A
Authority: EP
Inventors: Herbert O. Hultin; Yuming Feng
Original assignee: University of Massachusetts UMass
Current assignee: University of Massachusetts UMass
Priority date: 1999-07-16
Filing date: 2000-07-10
Publication date: 2002-04-17
Also published as: RU2002103868A; WO2001005251A1; AU6082800A; CA2375933A1; CN1373638A

Abstract

The invention relates to commercial grade food protein gels containing low amounts of animal muscle protein and salt, and methods of producing them.

Description

EDIBLE ANIMAL MUSCLE PROTEIN GELS

Field of the Invention

The invention relates to edible protein gels.

Background of the Invention A significant portion of retail packaged food products in the world includes edible muscle protein gels, for example, hot dogs in the United States and fish cakes in Japan. In general, a high animal muscle protein and salt concentration is required for the formation of an edible gel having commercially valuable properties. For example, a typical retail edible gel may contain 20% protein and 2-3% sodium chloride.

Commercially valuable gel properties include favorable textures and the ability to retain gel shape or water content after chopping and/or cooking. The raw material expense in manufacturing these products can be decreased if the same commercially valuable properties could be achieved in a gel having a lower concentration of animal muscle protein. In addition, gel food products having less salt may be more appealing to health conscious consumers.

Summary of the Invention

The invention is based on the discovery that edible gels of high quality can be formed from mixtures with relatively low muscle protein content and at very low or no salt conditions. The enhancement of the gelling capability of the muscle proteins is believed to be due to the reduction of salt and the increase in the net charge of the proteins. The new gel forming process requires mixing minced animal muscle with water, and adjusting the pH of the water to greater than about 6.7 or less than about 3.8 and the salt concentration of the water to less than 50 mM (e.g., less than 25 mM). Gels formed from this process exhibit high physical strength and water retention capacities after cooking. Thus, high gel quality can be obtained at reduced protein content. Accordingly, the invention features a method of forming a gel by (a) washing minced animal muscle (e.g., fish or poultry muscle) with wash water; (b) mixing the washed minced animal muscle with gel water to form a mixture so that an aqueous portion of the mixture contains less than 25 mM (e.g., less than 10 mM) salt and has a pH of greater than 6.7 (e.g., 7.4 to 8.5); and (c) heating the mixture to a temperature sufficient to form the gel. The pH and the salt concentration of the gel water can be adjusted after forming the mixture, and, in step (d) the mixture can be heated to at least 70°C for at least 2 minutes to kill bacteria, including Listeria. The invention also includes a method of forming a gel by (a) washing minced animal muscle with wash water; (b) mixing the washed minced animal muscle with gel water to form a mixture so that an aqueous portion of the mixture contains less than 25 mM (e.g., less than 10 mM) salt and has a pH of greater than 6.7 (e.g., 7.4 to 8.5) or less than 3.8 (e.g., 3.5 to 2.0), and the mixture has an animal muscle protein content of greater than 6%; and (c) heating the mixture to a temperature sufficient to form the gel.

In another aspect, the invention includes gels having a variety of commercially favorable properties. These gels can be formed using the methods of the invention. For example, the invention includes a gel having an animal muscle protein (e.g., fish or poultry muscle protein) content of greater than 6% (e.g., greater than 14%, or 7% to 13%), water, and a salt content of less than 25 mM (e.g., less than about 20 or 10 mM). The salt concentration measured immediately after gelation. The pH of the gel can be less than about 3.8 (e.g., 3.5 to 2.0). In another example, a gel of the invention can have an animal muscle protein content of at least 1% (e.g., at least 6%, or 9% to 30%), water, a salt content of less than 25 mM (e.g., less than 10 mM), and a pH greater than about 6.7 (e.g., about 6.7 to 7.4).

Also included in the invention is a heat-stable gel having an animal muscle protein (e.g., fish or poultry muscle protein) content of about 7-13% (e.g., about 9% to 13%) and water. This gel retains at least 85% (e.g., at least 95%) water after heating at 90°C for 20 minutes. Another gel of the invention has an animal muscle protein (e.g., fish or poultry muscle protein) content of at least about 8% (e.g., 9% to 11%) and a water content of at least 85%, in which the gel exhibits a strain value of at least 1.5 (e.g., at least 1.9) as measured by a torsion tester. All gels of the invention can be free of cryoprotectants. Yet another gel of the invention has an animal muscle protein content of at least 1% (e.g., at least 6%), water, a salt content of 25 to 50 mM salt, and a pH of greater than about 7.4.

The concentration of salt in a medium (e.g., water or a gel) is determined by comparing the conductivity of the medium with the conductivity of one or more reference media containing a known salt concentration at the same pH. The water or moisture content can be measured by any means known in the art, such as the method described in the Examples below.

The wash water used in the new methods is, in general, free of salt but can contain other additives such as preservatives. Suitable wash water includes tap water and deionized water. The gel water is used to form the muscle protein slurry or mixture that is to become the gel. Gel water can contain a variety of additives, so long as the gel water contains less than 25 mM salt and has a pH of greater than about 6.7 or less than about 3.8 after mixing with the muscle. The salt or pH of the gel water can be adjusted before, during, or after mixing with the minced animal muscle.

The methods of the invention are useful in producing commercial quality muscle protein gel food products using less raw animal muscle and low salt, thereby realizing cost savings for the manufacturer. The new protein gels of the invention, especially at reduced protein concentrations, can be formed by the methods of the invention and exhibit beneficial properties, such as low salt concentrations, high physical strength when compared to high salt gels with the same protein content, and high water retention capacity after cooking.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although suitable methods and materials for the practice or testing of the present invention are described below, other methods and materials similar or equivalent to those described herein, which are well known in the art, can also be used. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.

Detailed Description The invention relates to a method of forming a gel from animal muscle protein, the gel exhibiting commercially beneficial qualities. In general, the method includes washing minced animal muscle with wash water to reduce the salt concentration. Water can be added to adjust the gel water content. The gel water in this mixture is or has been adjusted so that it contains less than 25 mM salt and has a pH greater than about 6.7 or less than about 3.8.

It is believed that increasing the pH value of the mixture to above 6.7 (e.g., above 6.8, 6.9, 7.0, or 7.4) or decreasing the pH value of the mixture to below 3.8 (e.g., below 3.7, 3.6, or 3.5) is sufficient to increase the electrostatic repulsive forces and thus the osmotic potential of the muscle proteins. The presence of salt reduces this effect. In general, within these pH ranges, higher quality gels are formed at higher concentrations of animal muscle protein (e.g., 1- 30% protein) and at lower concentrations of salt (e.g., less than 25 mM salt, especially less than 20 or 10 mM salt). The lower the salt concentration, the better the gel.

Using the methods of the invention, gels having low protein content (defined as lower than presently commercially available animal protein gels, e.g., 13% protein) exhibit rheological properties (e.g., a strain of greater than 1.5, especially greater than 1.7, 1.9, or 2.1) comparable to commercial protein gel products such as hot dogs, which have at least 20% muscle protein. An advantage of the methods of the invention, therefore, is the ability to form commercial quality gels containing less protein than was previously possible.

Although the gels formed by the methods initially contain very low or no salt because the aqueous portion of the gel contains less than 25 mM salt, the gel can be soaked in solutions of different salt concentrations and pH values desirable in a final food product. These solutions can also contain various flavorings, colorings, or preservatives as described below.

Methods of Forming a Gel

The various steps of the methods of the invention can be carried out by procedures well known in the art. The animal muscle protein can be obtained from any animal muscle tissue, including poultry (e.g., chicken or turkey) and fish (e.g., fatty or lean fish, such as pelagic fish and cod, respectively), Crustacea (e.g., shrimp or crab), molluscs, beef, pork, and lamb. This animal muscle can be ground and homogenized using standard laboratory or industrial equipment.

For example, chicken breast meat can be obtained as follows. The breast meat is cut into cubes and ground through a meat grinder fitted with a plate having 5 mm diameter holes. The ground chicken breast muscle is then homogenized with wash water (1 :10 w/v) in a Waring blender (Dynamics Corp., New Hartford, CT) for 30-120 seconds and washed one to six times with cold (4- 6°C) deionized water. The washing should be sufficient to remove enough of the salt in the muscle so that the aqueous portion of the final mixture of homogenate and gel water contains less than 25 mM salt. It is noted that all muscle tissue inherently contains about 150 to 200 mM equivalent salt. Residual wash water can be removed by centrifugation or decantation.

The animal muscle homogenate is then mixed or chopped with gel water optionally containing one or more additives. Such additives include cryoprotectants (e.g., disaccharides), flavorings (e.g., spices such as pepper or herbs), food colorings, acids (e.g., citric acid, acetic acid, lactic acid, malic acid, tartaric acid, hydrochloric acid, or sulfuric acid), bases (e.g., NaOH or NaHCO₃), buffers, (e.g., phosphate salts such as sodium tripolyphosphate), chelating agents (e.g., EGTA or EDTA), cationic and anionic polymers, and water-binding agents (e.g., starch, soya, and milk proteins). The acids, bases, or buffers should be sufficient to achieve a pH of greater than 6.7 or less than 3.8 for the aqueous portion of the mixture (i.e., mixture pH). One or more of these additives can also be present in the wash water. It is also possible that sufficient acid, base, or buffer be present in the wash water and infused into the minced muscle or homogenate to maintain a mixture pH of greater than 6.7 or less than 3.8 without any buffers, acids, or bases added to the gel water. Whatever the additives present in the wash or gel water, the salt concentration of the aqueous portion of the final mixture should not exceed 25 mM.

Generally, the mixture is first formed or packed into a container before heating. The mixture of gel water and homogenate is then heated to form a gel. The exact times and temperatures sufficient to form a gel will depend on the source of the animal muscle protein, the nature of the additives, and the texture of the food product desired. In addition, the heating conditions can be adjusted to kill microorganisms. For example, heating the mixture at 70°C for 2 minutes is generally sufficient to kill human pathogens in muscle tissue. Under other circumstances, a gel can be formed by packing the mixture into a metallic tube and placing the tube under hot water (e.g., above 70°C) for several minutes. The mixture can also be stuffed into a special casing that is permeable to ions. The salt in the mixture can be reduced by immersing the mixture in an aqueous solution that contains less than 25 mM salt. The solution can be either cold (e.g., at 5°C or less) or hot (e.g., at 70-90°C or more). The mixture can also be extruded into a solution of hot water to form a gel. The hot water can contain all the necessary additives but generally with a salt concentration less than 25 mM. Various cooking methods can be used, including, for example, the use of hot water, steam, microwaves, ohmic heating, or heating under hydrostatic pressure. Heating can be performed in one or several stages and at different temperatures, which are typically in the range of 45-121°C. These heating steps are also referred to herein as cooking. The cooled gels can be soaked in solutions low in salt to increase their water content. Conversely, gels can be soaked in solutions high in salt and other solutes to dehydrate the gels. Cooked gels can also be placed in solutions at different pH values to adjust the pH of the cooked gels for reasons of taste, safety, etc. In a particular embodiment, the cooked gel is encased in a semi-permeable membrane (e.g., a sausage casing) and soaked in water to further decrease the salt concentration as desired. Because the casing limits the size of the gel and is semi-permeable, the gel cannot take up more water, but salt can flow from the gel into the soaking solution.

Physical Measurements

The salt concentration of the aqueous portion of the final mixture can readily be determined using standard procedures and equipment, such as conductivity meters. For example, a portion of the mixture can be diluted with distilled, de-ionized water and probed with a conductivity meter (YSI, Inc., Yellow Springs, OH), and the readings compared to a standard curve obtained from various known concentrations of a salt standard, such as NaCl. The measurement should be conducted at the same pH and temperature at which the standard curve is made. Although the conductivity of the mixture is likely conferred by a number of different salts, the comparison to a standard curve obtained from a single salt is sufficient for estimating total salt concentration. Similarly, the mixture pH can be readily determined using standard pH meters or other pH indicators, such as dyes or strips of pH paper. The concentration of protein in any mixture or solution can be determined using standard methods, such as the Bradford assay.

The quality of an animal muscle protein gel can be determined or estimated using a variety of measurements. Two critical measurements are the stress and strain values at failure. Stress and strain values are specific to the type of strain applied to the gel and the instrument setup. Two types of commonly used instruments are the Rheo Tex (Sun Science Co., LTD, Japan) and a torsion tester (Brookfield Digital Viscometer, model DV-II, Brookfield Engineering Laboratories Inc., Stoughton, MA). These methods are typically used for measuring the gel quality of commercial products that usually contain greater than 13% protein. Each methodology is described in Surimi Technology, Marcel Dekker, Inc., New York, 1992, Lanier et al., eds..

The Rheo Tex uses a sphere probe of stainless steel with a diameter of 5 mm. The probe penetrates a gel segment of 25 mm in length at one end until the gel fractures. The depth of the probe in the gel at fracture is called deformation (usually in cm), which is related to the strain value of the gel. The strain value, in turn, is generally an indicator of protein quality and is not substantially dependent on the protein content of the gel. High quality gels typically exhibit strain values greater than 1.0 (greater than 1.9 for the torsion tester described below).

The force that is required to break the gel is called the breaking force (usually in X g), which is related to the stress value of the gel. The stress value, in turn, is an indicator of tenderness and is substantially dependent on the water content of the gel. Stress values can vary greatly among similar gels and are not necessarily related to gel quality. However, in general, a good stress value can be greater than 10 kPa, for example, greater than 20, 30, 40, or 50 kPa. A gel of the invention can be from 10 to 40 kPa. In the surimi industry, the product of the deformation and breaking force is commonly used as an indicator for gel strength.

In the torsion tester, a gel segment of 28.7 mm in length and 18.6 mm in diameter is milled into a dumbbell-shaped specimen with a minimum center diameter of 10 mm. Plastic discs (Piedmont Plastics, Charlotte, NC) are glued to the specimen, which is then mounted to the torsion viscometer connected to a computer. The degree of rotation allowed before gel fracture and the magnitude of the breaking force required for gel fracture are used to calculate the strain and stress values as described in Hamann, "Failure Characteristics of Solid Foods," In: Physical Properties of Foods, Bagley et al, eds., pp. 351-385, Van Nostrand Reinhold/AVI, New York, 1983. Stress and strain values are affected by the solid and liquid content of the gel. A strain value greater than 1.9 is considered a high quality product for making elastic surimi gels.

Rheological properties can also be monitored dynamically and non- destructively during the gelling process by employing a Bohlin Rheometer (Bohlin Instruments, Cranbury, NY). This method is capable of measuring the gelling capability at reduced protein content (e.g., 2-10%). The rheological properties of a gel can be described in terms of its storage modulus (G'), the loss modulus (G"), and the phase angle (θ). The final G', measured after heating and cooling, is often used as an indicator for the gel strength because G' represents the elastic component of the strength measurement of a viscoelastic material, such as a protein gel. Since G' is based on a non-destructive (i.e., does not lead to fracture) force, the G' value will be less than the stress value obtained by gel fracture, as described above. However, G' should be proportional to the stress value obtained at fracture. Therefore, gel-forming ability can be compared among different samples under the same experimental conditions and using the same measuring devices, even if measurements under different conditions might not be comparable. In general, the higher the G' values, the higher the gel strength. The G' of a good gel is generally above about 5 kPa. The Bohlin rheometer is fitted with a pair of coaxial cylinders. The diameter of the inner cylinder (called the bob) can be 25 mm, and the internal diameter of the outer cylinder (called the cup) can be 27.5 mm. A sample is loaded into the gap between the cylinders, and the gelation monitored at a fixed frequency (e.g., 1 Hz) and at a maximum shear strain (e.g., 0.01). A rotational strain transducer in combination with a torsion bar can measure the torque transmitted through the sample between the cup and bob. Signals from the oscillatory drive and the resulting torque are gathered by a computer, which also controls the rheometer.

The quality of an animal muscle protein gel can also be evaluated by measuring water holding capacity (i.e., 100% minus percent loss in water content after a manipulation). The higher the water holding capacity, the more favorable is the gel as a food product. One way to calculate the percentage loss of water after a manipulation is to measure the water content before and after a manipulation. The water content is determined by weighing a gel sample, drying the gel at 105°C for at least 18 hours, and weighing the dried gel. The water content is calculated from the difference in mass after drying. One common manipulation is cooking (e.g., at 90°C for 30 minutes), and then measuring the cooking loss. Another is pressing a 3 mm gel slice under a weight of 3 kg for one minute. The gel slice is sandwiched between five layers of P5 medium porosity filter paper (Fisher Scientific, Pittsburgh, PA) to absorb any released water.

Other common manipulations include pressing or centrifuging and freezing and thawing. A good quality gel generally has a water holding capacity of at least about 70%, for example, at least about 80, 85, 90, or 95%.

Use of Gels

The gels of the invention can be packaged and sold as is or as a component of retail food products. For example, white meat chicken gels can be formed into cylinders and sold as low sodium, low fat hot dogs. Cod meat can be formed into blocks and sold as Asian fish cakes to be used in home-made soups. Alternatively, the gels can be sold to high value-added food manufacturers or packagers as ingredients in canned soups or stews, ramen, fresh salads, or Asian snacks.

Examples The invention will be further described in the following examples, which do not limit the scope of the claims.

Example 1 : Effect of Salt Concentration and pH on Gel Formation

Adult chickens were obtained from the Department of Veterinary and Animal Sciences at the University of Massachusetts. The birds were sacrificed by carbon dioxide asphyxiation. Breast muscles were taken from the birds, packaged in plastic bags, and placed on ice immediately.

Connective tissue was removed to the extent possible, and the remaining muscle was cut into small cubes. The muscle was then passed through a meat grinder fitted with a plate having 5 mm diameter holes. The ground muscle was mixed by hand in a beaker for 2 minutes.

Twenty grams of washed meat was then mixed with 200 ml of cold (4- 6°C) deionized, distilled water and homogenized in a commercial grade Waring blender (Dynamics Corp., New Hartford, CT) for 60 seconds. The homogenate contained 90% water and 10% muscle tissue, resulting in about 2% total protein. The homogenate was washed twice, each time with 200 ml of cold (i.e., 4-6°C) deionized water. The wash water was removed by decantation after sedimenting the protein at 15,000 x g for 20 minutes. The washed minced muscle contained approximately 85% water and 1.85 mM salt, as measured using a conductivity meter (YSI, Inc., Yellow Springs, OH), and had a pH of 5.78.

The water content of the homogenate or slurry was raised to 89%, and the slurry was chopped and mixed for another 30 seconds. The pH of the slurry was then adjusted up with 1 M NaOH or down with 1 N HC1 to the pH values specified in Table 1. The slurry was further chopped for 20 seconds after the addition of acid or base. The salt concentration of the final slurry was also measured to account for the contribution of NaOH in high pH slurries.

The resulting pH-adjusted slurry was stuffed into a commercial cellulose casing (Hot Dog Casings, The Sausage Maker, Inc., Buffalo, NY) and cooked at 90°C for 20 minutes. After cooking, the gel was immediately placed into ice water for 30 minutes and then stored in a 5°C cold room.

Stress and strain values for gels formed from slurries having various pH values were obtained using a torsion test. Gels were allowed to equilibrate to room temperature (15-20°C) prior to milling into dumbbell-shaped specimens as described in Surimi Technology, supra. Specimens had a minimum center diameter of 10 mm, length of 28.7 mm, and an end diameter of 18.6 mm. The ends of the specimens were glued to plastic disks (Piedmont Plastics, Charlotte, NC) with instant Krazy Glue (Elmer's Products, Inc., Columbus, OH) and mounted on a torsion apparatus consisting of a Brookfield digital viscometer (Model DV-II, Brookfield Engineering Laboratories Inc., Stoughton, MA). The viscometer was operated at 2.5 rpm, and the results were recorded on a chart recorder. Shear stress and shear strain were calculated using equations recited in Hamann, supra. A Ball Game Treat^® hot dog (Jordan's) was used as a reference gel.

The quality of animal muscle protein was first determined by measuring water content after a manipulation (i.e., 100% minus percent loss in water content after cooking, or after cooking and pressing). The higher the water holding capacity after a manipulation, the less water will be lost during consumer manipulations, such as cooking or chopping, and thus the more commercially attractive the gel. The water content of a gel was determined by weighing a gel sample, drying the gel at 105°C for at least 18 hours, and weighing the dried gel. The water holding capacity is reflected in the percentage difference in water content, relative to beginning gel mass, before and after a manipulation.

One manipulation was cooking at 90°C for 30 minutes. Another was pressing a 3 mm gel slice under a weight of 3 kg for 1 minute. Five layers of P5 medium porosity filter paper (Fisher Scientific, Pittsburgh, PA) was sandwiched between the weight and the gel to absorb any released water. The results are summarized in Tables 1 and 2, respectively.

Table 1 .

After cooking, the quality of 1 1-12% protein gels formed from low and high pH slurries was, on balance, comparable to or better than those of a commercial hot dog usually containing more than 22% protein. For example, the strain values for some of these gels exceeded 2.00, whereas the hot dog exhibited a strain of only 1.84. Clearly, the methods described herein were able to achieve retail quality protein gel products with substantially less protein.

The water content of the slurries, gels, and gels after pressing were also determined, and the results summarized in Table 2.

Table 2 .

Again, the high water holding capacity of the experimental gels was confirmed by the low water loss after pressing, for gels made at pH values at or above 7.1 and below 3.8.

The ability of a food to withstand freeze/thaw cycles is a commercially beneficial property, allowing ease of storage and shipping for the manufacturer, as well as the retailer. Therefore, the ability of the gels described immediately above to withstand freeze/thaw cycles was also examined. Gels were completely frozen at -20°C and then brought to room temperature. The water content of the gel before and after freezing was then determined, and the results summarized in Table 3.

Table 3 .

The results indicated that, with respect to water content, the gels withstood freezing and thawing well, with the greatest water loss leading to a change of only about 3% change in water content for the pH 3.68 gel. Therefore, the gels of the invention can be stored or shipped as frozen products with little damage or deformation.

Example 2: Effect of Protein Concentration on Gel Formation and Characteristics

To determine if gels can be formed from slurries containing muscle protein concentrations of less than 10%, no-salt slurries were prepared as in

Example 1 above. Separate slurry samples were adjusted to contain about 2%,

3%, 5%, or 10% muscle protein. The pH of each slurry was then adjusted to 7.2 by the addition of Na₂CO . The slurries were cooked at 72°C for 20 minutes to form gels. The gels were then cooled from 72°C to 35°C at a rate of l°C/min.

The storage modulus (G') was monitored. No viable gel could be formed by the

2% slurry at 35°C.

The rheological properties of viable gels were monitored during the heating and cooling processes. The final storage modulus (G') after heating and cooling were compared among samples of different protein concentrations. The 3% gel registered a G' value of less than 500 Pa, while the 5% gel exhibited a G¹ value of less than 1000 Pa. The 10% gel was measured to be about 7000 Pa.

The data here suggested that gel-forming ability increases exponentially as the protein concentration increases. It is also noted that, although no visible gels were formed after heating very low protein slurries (1-2% protein concentration) at 70°C for 20 minutes, gels were observed after the heated protein suspensions were cooled to about 5°C.

Example 3 : Effect of Cryoprotectants on Gel Formation and Characteristics Cryoprotectants such as sorbitol or sucrose are often added to commercial surimi (minced and usually washed muscle tissue) to preserve the gelling capability of the proteins after freezing and thawing. To show that the addition of cryoprotectants does not deleteriously affect the gels of the invention, 5% and 10% muscle protein pastes were prepared as described in Example 2 above, except that the pH of the paste was adjusted to 6.8. The 5% and 10% pastes were then divided into two separate samples each. To one of the two divided samples, sorbitol and sucrose was added to achieve a 4% concentration of each cryoprotectant in the paste. The pastes were then cooked to form a gel, and the gel cooled as described in Example 2. The final storage modulus (G') was monitored after heating the paste at 72°C for 20 minutes, followed by cooling to 35°C.

For the 5% gel, the final G' increased from 1600 Pa (without cryoprotectants) to 2058 Pa (with cryoprotectants). A similar effect for the 10% gel was seen, with the G' increasing from 13,800 Pa (without cryoprotectants) to 15,500 Pa (with cryoprotectants). Thus, commercial cryoprotectants commonly used in food products significantly improve the physical properties of the gels of the invention.

The data in Examples 1-3 describe the use of a new method of producing edible gels made from mixtures containing little or no salt and at relatively low concentrations (e.g., 10%) of muscle protein, and yet have rheological properties comparable to commercial gel products containing higher concentrations of muscle protein (e.g., above 20%), such as hot dogs. The water-holding capacity of these new gels is much higher than that of the gels made from traditional methods at 2-3%) NaCl concentrations and containing the same percentage of muscle protein.

Other Embodiments It is to be understood that while the invention has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the claims. Other aspects, advantages, and modifications are within the scope of the following claims.

What is claimed is:

Claims

1. A gel comprising an animal muscle protein content of greater than 6% and water, wherein the gel contains less than 25 mM salt.

2. The gel of claim 1, wherein the gel comprises an animal muscle protein content of greater than about 14%.

3. The gel of claim 1, wherein the gel comprises an animal muscle protein content of about 7-13%.

4. The gel of claim 1, wherein the salt concentration is measured immediately after gelation.

5. The gel of claim 4, wherein the gel contains less than about 20 mM salt.

6. The gel of claim 5, wherein the gel contains less than about 10 mM salt.

7. The gel of claim 1 , wherein the pH of the gel is less than about 3.8.

8. The gel of claim 7, wherein the pH of the gel is about 3.5 to 2.0.

9. The gel of claim 1, wherein the animal muscle protein is fish muscle protein.

10. The gel of claim 1, wherein the animal muscle protein is poultry muscle protein.

1 1. A gel comprising an animal muscle protein content of at least 1% and water, wherein the gel contains less than 25 mM salt, and the pH of the gel is greater than about 6.7.

12. The gel of claim 11 , wherein the gel comprises an animal muscle protein content of at least about 6%.

13. The gel of claim 1 1 , wherein the gel comprises an animal muscle protein content of at least about 9% to 30%.

14. The gel of claim 1 1 , wherein the pH of the gel is about 6.7 to 7.4.

15. A heat-stable gel comprising an animal muscle protein content of about 7-13% and water, wherein the gel retains at least 85% of the water after heating at 90°C for 20 minutes.

16. The gel of claim 15, wherein the gel comprises an animal muscle protein content of about 9-11%.

17. The gel of claim 15, wherein the animal muscle protein is fish muscle protein.

18. The gel of claim 15, wherein the animal muscle protein is poultry muscle protein.

19. The gel of claim 15, wherein the gel retains at least 95% of the water after heating at 90°C for 20 minutes.

20. A gel comprising an animal muscle protein content of at least about 8% and a water content of at least 85%, wherein the gel exhibits a strain value of greater than 1.5 as measured by a torsion tester.

21. The gel of claim 20, wherein the gel comprises an animal muscle protein content of about 9-11 ).

22. The gel of claim 20, wherein the animal muscle protein is fish muscle protein.

23. The gel of claim 20, wherein the animal muscle protein is poultry muscle protein.

24. The gel of claim 20, wherein the strain value is at least 1.9 as measured by a torsion tester.

25. The gel of claim 24, wherein the gel is free of cryoprotectants.

26. A method of forming a gel, the method comprising (a) washing minced animal muscle with wash water; (b) mixing the washed minced animal muscle with gel water to form a mixture, wherein an aqueous portion of the mixture contains less than 25 mM salt and has a pH of greater than 6.7 or less than 3.8; and

(c) heating the mixture to a temperature sufficient to form the gel.

27. The method of claim 26, wherein the animal muscle protein is fish muscle protein.

28. The method of claim 26, wherein the animal muscle protein is poultry muscle protein.

29. The method of claim 26, wherein the aqueous portion of the mixture has a pH of about 7.4 to 8.5.

30. The method of claim 26, wherein the pH of the gel water is adjusted after forming the mixture.

31. The method of claim 26, wherein in step (c) the mixture is heated to at least 70°C for at least 2 minutes.

32. The method of claim 26, wherein the aqueous portion of the mixture contains less than 10 mM salt.

33. The method of claim 26, wherein the mixture comprises an animal muscle protein content of greater than 6%.

34. The method of claim 26, wherein the aqueous portion of the mixture has a pH of about 3.5 to 2.0.

35. A gel comprising an animal muscle protein content of at least 1% and water, wherein the gel contains about 25 to 50 mM salt, and the pH of the gel is greater than about 7.4.