MXPA06005172A - Acid-stable soy protein and fortified food or beverage - Google Patents

Abstract

A water-soluble acid stable soy protein, methods for making same and acidic food or acidic beverage fortified therewith. Particularly, this invention is useful in the pH range of 3.5 to 4.1 where other soy protein fortification methods do not work. The invention is comprised of a soy protein, a thermal treatment method to solubilize at least 90%of the protein, an acidification of the protein to a point preferably significantly below the iso-electric value, and a partial neutralization to bring the product proximal to the intended pH of the application it will be used in.

Description

STYLE PROTEIN STABLE IN ACID MEDIUM AND FORTIFIED FOOD AND BEVERAGES FIELD OF THE INVENTION The present invention concerns soy protein, and, more particularly, to stable soy protein in acid medium soluble in water, to methods for making stable soy protein in acid medium soluble in water, and to foods and beverages that they are fortified with stable soy protein in acid medium soluble in water.

BACKGROUND OF THE INVENTION The fortification of foods and beverages with proteins is desirable to balance the nutritional aspect of the product in many applications. Intrinsically, beverages are too high in carbohydrates and too low in protein to satisfy the replacement of beverage food or high protein contents by means of popular diet plans such as Atkins. Some foods such as yogurt when marketed in the market of nutritional foods also subsequently have the desired protein content. The protein fortification with soy proteins is particularly desirable because of the amino acid profile of the jack protein and because the soy proteins work very well in neutral pH applications where they are very soluble. In food and drink acids (for example, at pH less than about 4.5), the soy protein is much less soluble and can form precipitated microagglutinates which give the product a dry or "limestone" mouthfeel. Over time, the insoluble protein will be separated by sedimentation of low viscosity foods and beverages to form an undesirable and separate layer. Accordingly, a need persists in the art for soy protein that is soluble in water, stable in stable acidic environments, and that can be included in foods and / or beverages to fortify the food and / or drink with protein.

SUMMARY OF THE INVENTION The present invention provides a stable soy protein in acid medium soluble in water, and foods and beverages that include stable soy protein in acid medium soluble in water. The soy protein is soluble in water at a pH of less than the pH at which the destabilized soy protein is soluble in water. The stable soy protein in acid medium can be formed separately from the food or drink, or where desired, the stable soy protein in acidic medium can be formed in situ in the food or beverage provided to the food or drink is not affected adversely by the treatment of the soy protein to make it stable in an acid medium. Acid-stable soy protein is preferably designed for foods and beverages where the pH of the food or drink is lower than that of destabilized soy protein is normally soluble. The acid stable protein of the present invention can be used in acidic foods and beverages where the pH of the food or drink is about 4.5 or less, and where, because of the proximity of the pH of the acidic medium at the iso of the soy protein, that is, the pH at which the protein is less soluble, the fortification of the soy protein that is not stable in an acid medium is not satisfactory. In another aspect, the present invention provides foods and beverages that include stable soy protein in acidic medium. The acid-stabilized soy protein can be added to the food or drink to improve the protein content, or the acid-stabilized soy protein can be formed in situ in the food or drink. The present invention is particularly useful in providing acidic food or acidic beverages that are fortified with soy proteins. Methods for the fortification of food or beverages are also provided. The present invention also provides a method for the preparation of stable water soluble acidic soy proteins. The method includes forming a suspension of soy protein in a liquid; apply a heat treatment to the soy protein suspension for a time and under sufficient pressure to solubilize the soy protein in a liquid; cool the suspension and reduce the pressure at ambient pressure; adding acid to the soy protein suspension in an amount such that the pH of the solution is at or below the isoelectric point of the protein to form an acidified soybean protein suspension; mix the acidified soy protein suspension in a high shear mixer; and optionally, neutralizing the acidified solution with a base to the approximate pH of the intended use of the stable protein in acid medium soluble in water. Once formed, the stable soy protein in water soluble acid medium can be stored in any of a variety of ways, including as a liquid or as a solid, such as, for example, as a dry solid for sprinkling.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The present invention provides a stable soy protein in acid medium soluble in water. The soy protein according to the invention is particularly well adapted to fortify acidic foods or acidic beverages because the soybean protein is stable in an acid medium and will not separate or agglomerate to any appreciable extent, should it do so. The stable soy protein in acidic medium of the invention is soluble in water at a pH lower than the pH at which the protein is stable. The enzymatically modified soy protein known in the art, such as for example the enzymatically modified Iso 5 soy powder available from Nutriant, a division of Kerry Inc., can also be acid stabilized according to another aspect of the present invention. The enzymatically stable modified soy protein in acidic medium is also soluble in water and can also be used in acidic foods and acidic beverages In congruence with other embodiments of the invention, acidic foods and acidic beverages can be fortified with soy protein using Soy protein stable in acidic or water soluble medium, soy protein or enzymatically modified combinations thereof, described herein The method of fortifying said foods and beverages with stable soy protein in acidic medium comprises mixing the food or beverage selected with the stable soy protein in acidic water soluble medium, described herein The mixture can be achieved, for example, simply by mixing the food or drink with the stable soy protein in acid medium. stable soy protein in acid medium can be formed in situ in the food or drink, provided that the food or drink to not be damaged or destroyed. The present invention also provides an acid beverage comprising a stable soy protein in an acid medium soluble in water and also provides an acidic food product comprising a stable soy protein in acid medium soluble in water. As described above, the stable soy protein in acid medium is soluble in water at a pH of less than the pH at which the protein is stable in stable. Preferably, the stable protein in acidic medium is soluble in water at a pH of about 4.5 or less, more preferably at a pH of from about 3 to about 4.5 and even more preferably at a pH of from about 3.5 to about 4.1. Typically, about 90% of the stable soy protein in acid medium is soluble in water at a pH in the range of from about 3.5 to about 4.1. Generally, the stable soy protein in acid medium soluble in water, is prepared by acidifying a suspension of soy protein so that the pH of the suspension is at or is lower than the isoelectric point of the soy protein. Preferably, the acidification of the soy protein is at a pH significantly lower than the iso-electric point in order to increase the amount of stable protein in acid medium that is soluble in the suspension. It is also preferred to balance the pH achieved during acidification with the pH of the intended use of the stable product in acidic medium to decrease the neutralization that might be required to bring the pH of the stable protein in acidic medium close to the pH of the intended application. The preferred method for the preparation of stable soy protein in acid medium soluble in water comprises forming a suspension of soy protein in a liquid, applying a heat treatment to the soybean protein suspension for a time and under sufficient pressure to solubilize the soy protein in the liquid; cool the suspension and reduce the pressure at ambient pressure; add acid to the soy protein suspension in an amount such that the pH of the solution is at or below the isoelectric point of the protein to form a suspension of acidified soy protein; mix the acidified soy protein suspension in a high shear mixer; and optionally, neutralizing the acidified solution with a base to the approximate pH of the intended use of the stable soy protein in acid medium soluble in water. It will also be appreciated that the process described above may vary as desired, in order to be used to make the stable soy protein in acid medium soluble in water. For example, after the formation of the soy protein suspension in a liquid, the soy protein suspension can be acidified and the acidified soy protein suspension can be subjected to heat treatment and high shear mixing. Generally, heat treatment is preferred before acidification, since addition of the solution is from the isoelectric point of the protein when the solubilization step was employed, usually the best solubility was obtained. It will be appreciated that the soy protein can be stable in acid medium in situ in food and / or beverages. For example, the soy protein is added to the food or beverage and the heat treatment is applied to the food or drink modified with soy protein, preferably, at or near the pH of the food or drink, for a time and under sufficient pressure to solubilize the soy protein in the food or drink. Then, acid is added to the food or beverage in an amount such that the pH of the food or beverage is below the isoelectric point of the soy protein. The food or drink is then mixed in a high shear mixer, and optionally neutralized with a base, preferably at the natural pH of the food or drink. The method by which the soy protein suspension is formed is not critical to the invention. For example, the suspension can be formed from protein isolates, or it can be the soy suspension formed during the process used to make the protein isolate. Typically, the solids content of the soy protein is sufficiently low that the soy protein does not agglutinate during the heat treatment. For example, the soy protein can be solubilized in liquids preferably water, by adding the soy protein in powder form to a liquid such as water at a temperature of about 21.11 ° C (70 ° C).

° F) in a mixing tank with displaced wall liquids, such as the Groen pot or the like. When the native protein is used, it is preferable to adjust the ratio of protein to water to provide a percentage of solids by weight of proteins of 15% or less and, preferably of 10%. When an enzymatically modified soy protein is used, as is common in producing low viscosity beverages, the ratio of protein to water is preferably adjusted to provide a weight percent protein solids of about 20% or less, and preferably about 14% Preferably, the pH of the soy protein suspension is adjusted before the high shear stress heat treatment of the suspension. The pH is adjusted to a pH in the range such that the soy protein is soluble in the liquid and so that the protein does not exhibit Maillard browning reactions during the high shear heat treatment. If the pH is too low, the total dissolution of the soy protein will be difficult. If the pH is too high, the product will exhibit Maillard darkening reactions during the subsequent heat treatment. Typically the pH is adjusted to a pH from about 6.8 to about 7.4, preferably 7.2. The pH can be adjusted with a suitable base, such as potassium hydroxide or the like, or with a suitable acid such as phosphoric acid or the like. As necessary to achieve the desired pH. The temperature and pressure of the heat treatment of the soy protein suspension are preferably controlled to cause the soy solids in the suspension to become soluble in the liquid. The heat treatment is carried out at a temperature from about 65.56 ° C (150 ° F) to about 148.89 ° C (300 ° F) is suitable for solubilizing the soy protein in the liquid. A temperature of about 132.22 ° C (270 ° F) is preferred. Particularly preferred is a temperature of about 126.67 ° C (260 ° F). Similarly, heat treatment carried out at a pressure in the range from about 0.35185 (5) to about 4.9259 Kg / cm2 (70 psi) is suitable for solubilizing the soy protein. The retention time, which is the time for which the heat treatment is maintained at the pre-selected temperature and pressure, is typically from about 5 seconds to about 3 minutes, and is typically inversely proportional to the treatment temperature. A retention time of about one minute is preferred. Various mixers, pasteurization units and the like commercially available to assist in the practice of the method of preparing the stable soy protein in acidic water-soluble medium of the present invention. The use of such equipment is described below only for the purpose of illustrating the method of the present invention, and is not intended in any way to limit the scope of the invention or to exclude the use of other equipment in carrying out the invention. Consistent with the invention, at least 90% of the soy protein is solubilized by forming a soy protein suspension at about 15% solids or less (about 20% solids or less in the case of soy protein) enzymatically modified) to, preferably, a pH of 7.2, and high shear heat treatment applied to the suspension. A too high solids content (eg, greater than about 20% of the native protein) can cause protein agglutination during heat treatment. Accordingly, the solids content is selected to avoid agglutination of the protein during the heat treatment. The soy protein suspension is then subjected to heat treatment such as, for example, by recirculating the suspension through high shear mixing equipment., such as a Silverson pump, until the temperature of the recirculation suspension / solution has reached approximately 93.33 ° C (200 ° F). The heat treatment may also be carried out with an indirect UHT steam pasteurization unit, such as a Unitherm, until the temperature of the recirculating suspension / solution reaches approximately 110 ° C (230 ° F), preferably at a pressure of approximately 1.4076 to 2.11 Kg / cm2 (20 to 30 psi) under turbulent flow, and then cooled to approximately 10 ° C (50 ° F) before leaving the unit. The heat treatment can also be carried out with a UHT direct steam sterilization unit until the temperature of the recirculating suspension / solution reaches approximately 132.22 ° C (270 ° F) at a pressure of 4.22 Kg / cm2 (60 psi), followed by a pressure relief to vent the product back to atmospheric conditions. After heat treatment, the solubility of the protein was evaluated. In the preferred methodology, the thermally treated soy protein solution is centrifuged at 5000 times the force of gravity for 2 minutes. The amount by weight of solids present in the liquid decanted from the trainer in proportion to the total amount of protein present in the sample represents the percentage of solution. If the desired amount of protein solubility is not achieved, for example, in the order of at least about 70%, preferably in the order of at least 80%, and more preferably in the order of about 90%, the protein solids they are diluted with water and subsequently heat treated to improve the percentage of soy protein that is solubilized. After the solubilization process, the temperature was reduced to 21.11 ° C (70 ° F) by means of a jacketed cooling tank or a continuous in-line sliding wall cooler such as a Thermitator or the like to prevent the aromas from burning after the development. After achieving solubility, the solution is acidified, preferably with phosphoric acid, at a pH lower than the isoelectric point of the soy protein. Acidification is made below the iso-electric point, the best solubility of the stable protein in acid medium will be in water. However, preferably the acidification is so great that excessive subsequent neutralization is required to bring the pH of the stable protein in acidic medium to the pH of the desired application. Other acids such as hydrochloric or citric acids can be used, but phosphoric acid is preferred because it tends to prevent the precipitation of the protein, possibly via disruption of the hydrogen bond in the protein from the phosphate anion. Preferably, the solution is acidified to a pH of about 3.3 or less. During the acidification process, it is desirable to apply high shear mixing to prevent agglutination as it passes through the isoelectric point of the protein. After solubilization and acidification of the soy protein suspension, it is desirable to re-evaluate the solubility by the centrifugation analysis described above. If less than 90% of the protein is soluble, the solution would be further acidified, such as at a pH of 3.0 and re-evaluated solubility. The pH of the intended application food or drink of the stable soy protein in water soluble acid medium of the present invention was evaluated and the pH of the stable soy protein in acid medium to be added thereto is adjusted to reasonably match the food or drink of intended application. Fruit beverage applications are typically at a pH in the range of about 3.5 to about 4.1. Typically for such applications, the pH of the stable soy protein in acid medium is increased using a base or regulator, such as potassium hydroxide (25% solution), trisodium phosphate buffer, or the like. The pH of the stable soy protein in acid medium may remain below the iso-electric point of the protein, for example, pH of about 4.5, to provide long-term shelf stability of the stable soy protein product in acid medium. The stable soy protein in acidic medium can be used as a liquid directly in the application, condensed by treatment with an evaporator, or dried, preferably spray-dried, for use at a later point in time or location. It is possible to effect the described thermal stabilization step at the lower pH of the soy protein solution after acidification. However, the thermal treatment at low pH is not particularly preferred since the addition to the solution is from the isoelectric point of the protein when the solubilization step is employed, the best solubility is obtained. The following examples are illustrative of, but not limited to, the present invention. Example 1 This Example illustrates the preparation of stable soy protein in acid medium soluble in water. In this example, the soy protein is prepared using the high shear cooking method. Ingredient Percent by weight Iso 3 soy protein powder (80% protein) 10.00 Phosphoric acid (25%) 0.03 Potassium hydroxide (25%) 0.01 Water 89.97 In this Example, Iso 3 soy protein powder was obtained from Nutriant (a division of Kerry Inc.) phosphoric acid and potassium hydroxide from TAB Chemicals. Iso-3 soy protein powder is reconstituted in water in a Stephan Model 11 mixer with the indicated water at 70 ° C. the pH is recorded and adjusted if necessary to 7.1. Sodium hydroxide diluted to increase, diluted phosphoric acid for lower). The solution is heated to 130 ° F, and pumped with a Triclover positive feed pump model PR 310M-U-UC6-S-T to a Silverson Model 425LS high shear inline mixer. The mixing pump is adapted with a recirculation circuit and a back pressure valve so that it makes multiple passes of the product through the pump before leaving the process. The speed of the Triclover feed pump is adjusted so that the residence time of the product in the circuit results in an increase in temperature to approximately 200 ° C. The product is then verified for soluble protein as described above, then cooled to approximately 70 ° F in the Stephan model 11 using cold water circulated through the outer jacket of the tank. The product is titrated to a pH of approximately 3.3 using 25% phosphoric acid in the mixer Stephan, while vigorously shaken, is then titrated at a higher pH of about 3.8 with 10% potassium hydroxide. The resulting solution is adjusted to approximately 130 ° F, is homogenized through a Gaulin homogenizer model M-3 at a pressure in the first stage of 140.74 Kg / cm2 (2000 psi) and a pressure in the second stage of 35.185 Kg / cm2 (500 psi), then dried in a compact spray dryer with APV Anhydro 22039 centrifugal atomizer with an approximate inlet and outlet temperature of 162.78 ° C (325 ° F) and 79.44 ° C (175 ° F), respectively. Example 2 This Example illustrates the preparation of stable soy protein in acid medium soluble in water. In this example, the soy protein is prepared using a direct steam UHT process. Ingredient Percent by weight Soybean Curd - pH 4.5 (30% TS) 30.00 Phosphoric Acid (25%) 0.03 Potassium Hydroxide (25%) 0.01 Water 69.97 In this Example the soy rennet was obtained from the Nutriant soybean manufacturing process , phosphoric acid and potassium hydroxide from Chemicals The acidic soybean rennet was reconstituted with water in an APV Multivertor model CLV-25 with the indicated water at 70 ° F. The rennet was neutralized to pH 7.1 with dilute potassium hydroxide. The solution was adjusted to 130 ° F, and pumped through a Cherry Burell steam sterilizer model XLV UHT. The temperature of the product is adjusted to 285 ° F with a back pressure of 4.22 Kg / cm2 (60 psi) and a retention tube of a length such that the product has a residence time of approximately 30 seconds before entering the chamber snapshot. In the instantaneous chamber, the enthalpy of the released steam reduces the product temperature to approximately 98.89 ° C (210 ° F).

The product temperature is then lowered to 21.11 ° C (70 ° F) with a Cherry Burrell model 6 x 36 BWS Votator 2 with glycol cooling jacket. The product is then verified for soluble protein as described above. The product is titrated using 25% phosphoric acid to a pH of about 3.3 in a Multivertor while being vigorously stirred, then titrated to a higher pH of about 3.8 with 10% potassium hydroxide. The resulting solution is adjusted to approximately 130 ° F, homogenized through a Gaulin homogenizer model M-3 at a first stage pressure of 140.74 Kg / cm2 (2000 psi) and a second stage pressure of 35.185 Kg / cm2 ( 500 psi), then dried in a compact spray dryer with APV Anhydro 22039 centrifugal spray with an inlet and outlet temperature of 162.78 ° C (325 ° F) and 79.44 ° C (175 ° F), respectively. Example 3 This Example illustrates a beverage fortified with stable soy protein in acid medium soluble in water.

Ingredient Percent by weight Concentrated White Grape Juice of 67 degrees Brix 8.00 Concentrated Apple of 70 degrees Brix 4.00 Peach Concentrate of 70 degrees Brix 2.00 Stable soy powder in acid medium (spray drying, pH 3.8) 3.50 Sacaralose 0.08 Peach Aroma 0.80 Aroma of Vanilla 0.40 Yellow of turmeric soluble in water at 10% Monosodium phosphate 0.10 Water-soluble anatoxide at 10% 0.04 Water 80.78 In this Example, the juice concentrates were obtained from Treetop Inc., the sucralose from Splenda Inc., the aroma of peach from Sunpure Inc., vanilla from Virginia Daré, monosodium phosphate from FMC, and color (turmeric yellow and anato) from Chris Hansens Inc. The stable soy protein in acidic medium dissolves in water using a jacketed tub with 5-gallon steam and a high-shear agitator. Then the other ingredients were added and mixed for 5 minutes. The temperature was increased to 73.89 ° C (165 ° F) for 1 minute and the product was homogenized (with a Gaulin model M-3) at a first stage pressure of 140.74 Kg / cm2 (2000 psi), a second stage pressure of 35,185 Kg / cm2 (500 psi) [in total 175.93 Kg / cm2 (2500 psi)]. The product was put back in the jacketed tub and cooled to 60 ° C and stored under refrigerated conditions for up to 4 weeks. Example 4 This Example illustrates a beverage fortified with stable soy protein in acid medium soluble in water. Ingredient Percent by weight White Grape Juice Concentrate of 67 degrees Brix 8.00 Concentrate of apple of 70 ° Brix 4.00 Concentrate of peach 2.00 Protein of soybean Modified Enzymatically in Powder Iso 5 3.50 Sacaralose 0.08 Aroma of Peach 0.80 Vanilla aroma 0.40 Yellow 10% water-soluble turmeric 0.40 Monosodium phosphate 0.20 Water-soluble anatoxide 10% 0.04 Water 80.78 In this Example, the juice concentrates were obtained from Treetop Inc., the enzymatic modified soy protein Iso 5 from Nutriant, the sucralose from Splenda Inc., the peach aroma from Sunpure Inc., the vanilla from Virginia Daré, the monosodium phosphate from FMC , and the color (turmeric yellow and anato) of Chris Hansens Inc. The soy protein dissolves in water using a 5 gallon steam jacketed tub and a high shear agitator. Then the other ingredients were added and mixed for 5 minutes. The pH was checked and adjusted to about 3.8 using phosphoric acid to knock down the pH or potassium hydroxide to increase the pH. In this Example, a higher level of monosodium phosphate was used in order to increase the phosphate concentration of the fortified drink and as a supplement to the lower phosphate content of the soy protein powder Iso 5 (not stable in acid medium). . The product is then processed with a Tetra Therm Aseptic VTIS direct steam UHT sterilizer, where it is preheated in a plate heat exchanger at approximately 80 ° F, then further heated with steam injection at 285 ° C - under retropressure 3.5185 Kg / cm2 (50 psi). After a retention period of approximately 5 seconds, it enters the instantaneous chamber, where the enthalpy of the released steam lowers the temperature to approximately 98.89 ° C (210 ° F). The product is then homogenized with a Tetra Alex homogenizer and cooled in a plate heat exchanger at 50 ° F and is ready to pack aseptically.

Claims (52)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty, and therefore the content of the following is claimed as property: CLAIMS 1. A stable soy protein in water-soluble acid medium, characterized in that the soy protein is soluble in water at a pH lower than the pH at which the non-stabilized soy protein is soluble. 2. A stable soy protein in water soluble acid medium, characterized in that the soy protein is soluble in water at a pH of about 4.5 or less. 3. The stable soy protein in water-soluble acid medium according to claim 2, characterized in that the soy protein is soluble in water at a pH of from 3 to about 4.5. 4. The stable soy protein in acid medium soluble in water according to claim 2, characterized in that the protein is soluble in water at a pH from about 3.5 to about 4.1. 5. The stable soy protein in acid medium soluble in water according to claim 1, 2, 3 or 4, characterized in that at least 90% of the protein is soluble in water at a pH from about 3.5 to about 4.1. 6. An acid beverage characterized in that it comprises a stable soy protein in an acid medium soluble in water, characterized in that the soy protein is soluble in water at a pH from about 3.0 to about 4.5. The beverage according to claim 6, characterized in that said beverage has a pH of 4.5 or less. 8. The beverage according to claim 6, characterized in that said beverage has a pH from about 3 to about 4.5. The beverage according to claim 6, characterized in that said beverage has a pH from about 3.5 to about 4.1. 10. An acidic food product characterized in that it comprises a stable soy protein in acid medium soluble in water, characterized in that said protein is soluble in water at a pH from about 3.0 to about 4.5. 11. The food product according to claim 10, characterized in that said product has a pH of 4.5 or less. 12. The food product according to claim 10, characterized in that said food product has a pH from about 3 to about 4.5. The food product according to claim 10, characterized in that said food product has a pH from about 3.5 to about 4.1. 14. A method for fortifying an acid beverage with soy protein, characterized in that the method comprises adding to said acid beverage a stable soy protein in acid medium soluble in water. 15. The method according to claim 14, characterized in that said soy protein is soluble in water at a pH of about 4.5 or less. 16. The method according to claim 14, characterized in that said soy protein is soluble in water at a pH from about 3 to about 4.5. 17. The method according to claim 14, characterized in that said soy protein is soluble in water at a pH from about 3.5 to about 4.1. 18. The method according to claim 14, 15, 16 or 17, characterized in that at least 90% of said soy protein is soluble in water at a pH from about 3.5 to about 4.1. 19. A method for fortifying an acidic food product with soy protein, characterized in that said method comprises adding to said food product a stable soy protein in acid medium soluble in water. The method according to claim 19, characterized in that said soy protein is soluble in water at a pH of about 4.5 or less. 21. The method according to claim 19, characterized in that said soy protein is soluble in water at a pH from about 3 to about 4.5. 22. The method according to claim 19, characterized in that said soy protein is soluble in water at a pH from about 3.5 to about 4.1. 23. The method according to claim 19, 20, 21, or 22, characterized in that at least 90% of said soy protein is soluble in water at a pH from about 3.5 to about 4.1. 24. A method for the preparation of stable soy protein in water-soluble acid medium, characterized in that it comprises: forming a suspension of soy protein in a liquid; apply a heat treatment to the soy protein suspension for a time and under sufficient pressure to solubilize the soy protein in the liquid. cool the suspension and reduce the pressure at ambient pressure; adding acid to the soybean protein suspension in an amount such that the pH of the suspension is at or less than the isoelectric point of the protein to form a suspension of acidic soy protein; mix the acidified soy protein suspension in a high shear mixer; and optionally, neutralizing the acidified solution with a base at the approximate pH of the intended use of the stable soy protein in acid medium soluble in water. 25. The method according to claim 24, characterized in that after the formation of the suspension of soy protein in a liquid, the suspension of soy protein is acidified and the suspension of acidified soy protein is subjected to heat treatment and mixing of high shear stress. 26. The method according to claim 24, characterized in that the solids content of the soy protein suspension is sufficiently low that the soy protein does not bind during the heat treatment. 27. The method according to claim 24, characterized in that the acid is added to lower the pH to about 3.3 or less. 28. The method according to claim 24, characterized in that the solids content of the soy protein suspension is less than about 20% by weight solids. 29. The method according to claim 24, characterized in that the solids content of the soy protein suspension is less than about 15% by weight solids. 30. The method according to claim 24, characterized in that the solids content of the soy protein suspension is less than about 10% by weight solids. 31. The method according to claim 24, 25, 26, 27, 28, 29 or 30, characterized in that the pH of the soy protein suspension is adjusted before the heat treatment with high shear stress of the suspension at a pH in the interval in which the soy protein is soluble in the liquid and such that the soybean protein does not exhibit Maillard darkening reactions during the high shear heat treatment. 32. The method according to claim 24, 25, 26, 27, 28, 29 or 30, characterized in that the pH of the soybean suspension is adjusted to a pH from about 6.8 to about 7.4. 33. The method according to claim 24, 25, 26, 27, 28, 29 or 30, characterized in that the pH of the soybean suspension is adjusted to approximately a pH of about 7.2. 34. The method according to claim 24, 25, 26, 27, 28, 29 or 30, characterized in that the soy protein suspension is the soy protein suspension formed during a process for making a protein isolate. 35. The method according to claim 24, 25, 26, 27, 28, 29 or 30, characterized in that said soy protein suspension is formed by mixing an isolate or dry protein concentrate with water. 36. The method according to claim 24, 25, 26, 27, 28, 29 or 30, characterized in that said soy protein suspension is heated to a temperature from about 65.56 ° C (150 ° F) to about 148.89 ° C (300 ° F) and under sufficient pressure to keep the suspension in the liquid state. 37. The method according to claim 36, characterized in that the temperature is approximately 132.22 ° C (270 ° F). 38. The method according to claim 36, characterized in that the temperature is approximately 126.67 ° C (260 ° F). 39. The method according to claim 36, characterized in that the pressure is from about 0.35 kg / cm2 to 4.93 kg / cm2 (5 to 70 psi). 40. The method according to claim 36, characterized in that the pressure is from about 3.5 to 4.
2. 2 Kg / cm2 (50 to 60 psi). 41. The method according to claim 36, characterized in that the temperature and pressure of the heat treatment is maintained for a retention time from about 5 seconds to about 3 minutes. 42. The method according to claim 36, characterized in that the retention time is approximately 1 minute. 43. A method for the preparation of stable soy protein in water-soluble acid medium, characterized in that it comprises: forming a suspension of soy protein in a liquid, said suspension having 15% by weight of solids or less; optionally, adjusting the pH of the suspension to a pH in the range of about 6.8 to about 7.4; heating the soy protein suspension at a temperature from about 65.56 ° C (150 ° F) to about 148.89 ° C (300 ° F), with a retention time from about 5 seconds to about 3 minutes and under pressure from about 0.35185 (5 psi) at approximately 4.9259 Kg / cm2 (70 psi) to solubilize the soy protein in the liquid; cool the suspension and reduce the pressure at ambient pressure; adding an acid to the soybean protein suspension in an amount such that the pH of the solution is at or is less than the isoelectric point of the protein to form an acidified soybean protein suspension; mix the acidified soy protein suspension in a high shear mixer; and optionally, neutralizing the acidified solution with a base at the approximate pH of the intended use of the stable protein in acid medium soluble in water. 44. The stable soy protein in water soluble acid medium according to claim 1, 2, 3, or 4, characterized in that said soy protein is enzymatically modified soy protein. 45. The acid beverage according to claim 6, characterized in that the soy protein stable in acidic water-soluble medium is an enzymatically modified soy protein. 46. The acidic food product according to claim 10, characterized in that the stable soy protein in water soluble acid medium is an enzymatically modified soy protein. 47. A method for the preparation of a food or drink comprising acid-stabilized soy protein, characterized in that said method comprises: adding soy protein or enzymatically modified soy protein to said food or beverage to form a food or drink modified with protein; apply a heat treatment to the food or drink modified with protein for a time and under sufficient pressure to solubilize the soy protein in the food and drink; cooling the heat-treated food or drink and reducing the pressure at ambient pressure; adding acid to the thermally treated food or beverage so that the pH of the food or beverage is at or is less than the isoelectric point of the protein to form an acidified soy protein food or drink; mix the acidified soy protein food or drink in a high shear mixer; and optionally, neutralizing the food or drink of acidified soy protein with a base. 48. The method according to claim 47, characterized in that first the acid is added to the protein modified food or drink so that the pH of the food or beverage is at or is lower than the iso-electric point of the protein to form a acidified soy protein food or drink, then the acidified soy protein food or drink is heat treated for a time and under sufficient pressure to solubilize the soy protein in the food or drink. 49. The method according to claim 24, characterized in that the acid is first added to the suspension of soy protein in liquid in an amount such that the pH of the suspension is at or is lower than the iso-electric point of the protein to form a suspension of acidified soy protein, followed by the application of a thermal treatment to the suspension of acidified soy protein for a time and under sufficient pressure to solubilize the soy protein. 50. An acid-stable, water-soluble soy protein characterized in that said soy protein is at least about 90% soluble in aqueous solution at a pH of 3.5. 51. A stable soy protein in water soluble acid medium characterized in that the soy protein is at least approximately 90% soluble in aqueous solution at pH 3.0. 52. An acid-stable, water-soluble soy protein characterized in that the soy protein is at least approximately 90% soluble in aqueous solution at a pH of 3.8.