Method for preparing disarmated soy protein material

Abstract

"METHOD FOR PREPARING DEAROMATIZED SOY PROTEIN MATERIAL". Soy derived materials such as soy milk, soy flour, soy concentrates, and soy protein isolates, are disarmed by adjusting the pH of an aqueous composition of these soy derived materials to about 9 to about 12 to solubilize the soa proteins and to release the flavoring compounds and then pass the pH-adjusted composition onto an ultrafiltration membrane having a molecular weight cut of up to about 50,000 Daltons under conditions where flavoring compounds pass through the membrane, leaving the soy material retained with improved aroma.

Description

“METHOD FOR PREPARING DEAROMATED SOY PROTEIN MATERIAL” FUNDAMENTALS OF THE INVENTION This invention generally relates to the processing of soy-derived materials for use in various food products. More particularly, the invention relates to a method for de-aromatizing soy materials in order to make them acceptable in a wide range of foods. In recent years, soy proteins have become widely used in food products due to the health benefits they offer. In some applications, the taste of soy materials is not objectionable. However, in some uses, such as dairy-like products, beverages, and others, the aromas found in soy materials may prevent their ready acceptance by the consumer. Thus, in order to extend the uses of soy materials, the present inventors wished to find a method to reduce the aroma components of soy materials. However, it was not evident that the methods previously used to remove aroma components from other organic materials could be successful in treating soy materials. Organic materials, because they have complex compositions, must be tested to determine if any given treatment method will be satisfactory. An example of methods previously employed for purifying organic materials is found in US Patent 4,477,480, in which the patent holders show that starch can be treated with an alkali to remove objectionable aroma components. In a commonly granted patent, US Patent 4,761,186, ultrafiltration is used to purify starch. In both cases, the aroma components are removed from the starch, in patent '460 by solubilizing the aroma components in such a way that they can be washed away from the relatively insoluble starch. In patent '186, ultrafiltration was used to remove aroma components as permeate, while the insoluble starch remained in aqueous suspension. In contrast, the present invention separates aroma components from soluble high molecular weight soy proteins. There are many articles and patents relating to the processing of soy materials in order to recover protein content while simultaneously reducing flavor compounds to make the proteins more acceptable in food products. However, these earlier descriptions were not specifically directed at the removal of flavor compounds and the recovery of protein as such, to the extent possible. One example is US Patent 4,420,425, in which soy protein components are solubilized at a pH of 7 to 11, preferably around 8, and after ultrafiltration through a membrane having a molecular weight cutoff above 70,000, the retained soy proteins are recovered by spray drying. In variants, only a portion of the protein is solubilized at lower pH values ​​and subjected to ultrafiltration with a membrane having a cutoff preferably above 100,000 molecular weight, the product having, as verified, improved color and aroma.A larger cutoff would be expected as it would result in a loss of valuable proteins. In another patent, US Patent 5,658,714, a soy flour suspension is pH adjusted in the range of 7 to 10 to solubilize proteins, which are then passed through an ultrafiltration membrane and phytate and aluminum are retained, probably as solids. Although the molecular weight cutoff of the membrane is not given, it is considered that the pore size was large in order to be able to pass the soluble proteins. Both patents contain extensive discussions of the efforts of others in processing soy materials; neither teaches nor suggests pH control during the ultrafiltration process. In the group of related patents, Mead Johnson Company describes processes for solubilizing soy proteins by raising the pH of an aqueous solution of soy materials and recovering the proteins, which, it is claimed, have a mild taste. The processes are primarily directed at concentrating proteins rather than removing flavoring compounds. In US Patent 3,995,071, the pH was raised to 10.1 to 14 (preferably 11 to 12) to solubilize soy proteins, after which the pH was lowered to about 6 to 10 and ultrafiltration with a membrane having a molecular weight cutoff of 10,000 to 50,000 Daltons was used to retain the proteins while discarding carbohydrates and minerals. In US Patent 4,072...In US Patent 670, emphasis was placed on the removal of phytates and phytic acid by solubilizing proteins at a pH of 10.6 to 14 and a temperature of 10 to 50°C to render the phytates and phytic acid insoluble, then separating them and finally acidifying the solution to a pH of about 4 to 5 to precipitate the soy proteins. In US Patent 4,091,120, soy proteins were solubilized at a pH lower than 10, preferably 7 to 9, and ultrafiltration was used to separate the proteins as retentate, while passing carbohydrates as permeate. These patents neither teach nor suggest pH control during the ultrafiltration process. The present inventors wished to remove compounds in soy materials that contribute to color and aroma and that interfere with the use of soy in some food products such as beverages, dairy analogues, and others. They found that soy-derived materials can be successfully treated using the process described below, recovering substantially all proteins and rejecting the compounds that cause undesirable color and aroma. Furthermore, by controlling the pH within the range of about 9 to about 12 during the ultrafiltration process, de-aromatized soy materials having improved functional properties can be obtained. Thus, the product is suitable for many food products. SUMMARY OF THE INVENTION Broadly, the invention is a process for preparing an aqueous soy composition having a soy concentration of about 1 to about 20 percent, which is adjusted in pH to solubilize the protein content and to release the flavoring compounds. Then, the composition is subjected to ultrafiltration, while maintaining pH control, using a membrane capable of retaining substantially all of the soy protein content while removing the flavoring components as permeate. Deflavored soy materials prepared by the present methods are ideally suited for use in dairy and non-dairy beverages, fruit drinks not subject to sediment, such as smoothies, wellness drinks, confectionery-type products, nutritional bars, cheeses, cheese analogues, dairy and non-dairy yogurts, meat products and meat analogues, cereals, baked goods, snacks, and others. In one aspect, the invention is a method for de-aromatizing soy-derived materials, such as soy milk, soy flour, soy concentrates, and soy protein isolates, the method of which includes preparing an aqueous composition of the soy material containing flavoring compounds, adjusting the pH in the range of about 9 to about 12 to solubilize the protein content of the soy material and release the aroma components, and then passing the adjusted composition at an adjacent pH to an ultrafiltration membrane having pores that provide a molecular weight cut-off of up to 50,000 Daltons, while maintaining the pH in the range of about 9 to about 12, thus retaining substantially all of the protein content, while passing through the pores the aroma-producing compounds. In another aspect, the invention includes adjusting the pH to the range of about 9 to about 12, using an alkali such as sodium, potassium, or calcium hydroxides, to solubilize the protein content and release the aroma components. Making it possible to separate these compounds by ultrafiltration, as importantly, the pH is also controlled in the range of about 9 to about 12 during the ultrafiltration process. In one embodiment, the invention is a method for de-aromatizing soy materials in a continuous process whereby a pH-adjusted aqueous mixture of soy materials is passed adjacent to an ultrafiltration membrane to separate the aroma components. The pH is maintained around 9 to about 12 during ultrafiltration by adding the appropriate amount of an appropriate pH-altering material (usually a base). The permeate containing aroma components and water is passed adjacent to a reverse osmosis membrane to remove water from the permeate, and the separated water is recycled to join the recycled retentate and the new pH-adjusted soy materials. A portion of the retentate is continuously removed and the de-aromatized soy materials recovered. In a preferred embodiment, the invention is a method for de-aromatizing soy materials in a batch or semi-continuous process whereby an aqueous mixture of pH-adjusted soy materials is passed adjacently through an ultrafiltration membrane, the permeate is separated for recovery of aroma components, and the retentate is recycled to combine with new pH-adjusted soy materials. Water is added periodically or continuously to replace water lost to the permeate and to adjust the concentration of soy materials in the combined stream to a predetermined level. If necessary, pH-altering material (e.g., a base) can be added to the recycled retentate, or water can be added to control the pH within the desired range during the ultrafiltration process. The process is continued until all aroma compounds have been removed. In a preferred embodiment, the present invention provides a method for preparing deflavored soy protein material. the aforementioned method comprising: (a) prepare an aqueous composition of a soy material containing soluble soy proteins, flavoring compounds and insoluble materials, (b) to solubilize the soy proteins by adjusting the aqueous composition of (a) to a pH in the range of about 9 to about 12 and releasing the flavoring compounds, (c) remove insoluble materials from the pH-adjusted aqueous composition of (b) to obtain a treated aqueous composition; (d) passing the treated aqueous composition of (c) adjacent to an ultrafiltration membrane having a molecular weight cutoff of up to about 50,000 Daltons, while maintaining the pH in the range of about 9 to about 12, under appropriate ultrafiltration conditions whereby the flavoring compounds pass through the membrane, thus deflavothing the soy material and retaining substantially all solubilized soy proteins, and (e) recover the solubilized soy proteins retained by the ultrafiltration membrane to obtain the dearomatized soy protein material. The ultrafiltration membrane used in the method of the invention will have a molecular weight cutoff of up to 50,000 Daltons, preferably 1,000 to 50,000, more preferably about 10,000, and is preferably a ceramic or polyethersulfone membrane. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of the intensity of aroma attributes of soy. Figure 2 is a graph of the intensity of unflavored soy milk compared to a control sample. Figure 3 is a graph of the intensity of another group of soy aroma attributes. Figure 4 is a graph of the intensity of deflavored soy concentrate and a control sample compared to the sample in Figure 3. Figure 5 is a graph of the intensity of deflavored soy concentrate and a control sample. Figure 6 is a graph showing the change in the concentration of flavoring compounds between a deflavored soy sample and a control sample. Figure 7 is a graph showing the change in the concentration of flavoring compounds between a deflavored soy sample and a control sample. Figure 8 is a block diagram of a process employing the invention. Figure 9 is a graph of the intensity of isolated aroma attributes of soy. Figure 10 is a graph of the intensity of deflavored soy isolate compared to a control sample. Figure 11 is a block diagram of a preferred embodiment of the invention. DESCRIPTION OF PREFERRED PERFORMANCE FORMS Soybean-derived materials. Soybeans are valuable sources of oil and, in the present invention, of protein. Soybeans contain about 40 percent protein, which has been classified by ultracentrifugation as 2S, 7S, 15S, and 15S (see also US Patent 4,420,425). These fractions may contain other materials as well, and they have a wide molecular weight range, from 3,000 to 600,000. It will be well known that soy products have undesirable odors and aromas that must be removed in order to make the soy materials widely usable in Food products. Lipoxygenases are believed to catalyze the oxidation of some polyunsaturated fatty acids, producing hydroperoxides that are degraded into volatile carbonyl compounds, associated with objectionable odors and aromas in soy-derived materials. Some of the compounds associated with soy aromas are described in Table C in Example 10 below. Although the protein content of soy-derived materials is considered a valuable fraction for use in food products, soluble carbohydrates are considered undesirable. Their removal from soy protein fractions is a goal in many processes where proteins are recovered. Phytates are compounds that are also considered undesirable in soy proteins. These compounds are calcium-magnesium-potassium salts of inositol hexaphosphoric acid. These compounds are believed to chelate metal ions and are not readily absorbed by the human body. They are thought to bind to soy proteins and interfere with digestion. As mentioned above, the removal of phytates has been a goal of workers in the field of soy-derived materials. Ultrafiltration Membranes. Filtration is used to separate many materials. In the present invention, ultrafiltration is used to remove flavoring compounds from soy-derived materials. Importantly, the pH of the soy-derived material must be maintained in the range of about 9 to about 12 during the ultrafiltration process. Ultrafiltration is intended to remove particles having a size between 10 and 1,000 angstroms (0.001 to 0.1 pm), generally corresponding to particles having a molecular weight between 10,000 and 1,000,000, and which may also be affected by the shape of these high molecular weight particles. Soy proteins have a molecular range between about 3,000 and 600,000. A membrane can be chosen which is capable of passing all soy proteins or only a portion. selected. In the present invention, soy proteins are retained by the ultrafiltration membrane under selected operating conditions, while lower molecular weight flavoring compounds pass through the membrane and are separated, thereby improving the color and aroma of the retained soy proteins and associated solids. A polymer ultrafiltration membrane can be defined as an anisotropic (non-uniform) layer. One face is a skin containing pores that determine the size of the molecules that pass through the membrane. The support for the surface skin is a spongy structure that extends onto the opposite face. These membranes are commonly made by coagulating the polymers in an aqueous bath. Typical polymers used include polysulfones, cellulose esters, poly(vinylidene fluoride), poly(dimethylphenylene oxide), and poly(acrylonitrile), which can be molded into membranes. Often, the membranes are formed into hollow tubes that are assembled into bundles, through which the solution to be filtered is passed. Alternatively, flat membrane sheets and spiral designs can be used. In commercial practice, pressure is applied to facilitate the movement of lower molecular weight compounds through the membrane.The membrane must be able to withstand the pressures used, making it important that the spongy support structure is uniform to prevent the surface skin from tearing and deviating from the membrane. In addition to the polymeric membranes described above, other materials have been used to make ultrafiltration membranes, such as ceramics, sintered metals, and other inorganic materials. The present invention is not limited to any particular type of membrane. Generally, the membrane must be able to pass flavoring compounds, which are believed to have molecular weights of less than 1,000 Daltons. More importantly, the membranes must be able to retain substantially all solubilized soy proteins. Thus, the membrane of the invention will have a molecular weight cutoff of about 50,000 Daltons, preferably about 1,000 to 50,000 Daltons, more preferably 10,000 to 30,000 Daltons. Process. The invention process includes the following steps: (1) prepare an aqueous mixture of soy-derived material; (2) add a base to raise the pH of the aqueous mixture to about 9 to about 12 in order to solubilize the soy proteins and release the flavoring compounds, (3) pass the pH-adjusted mixture, while maintaining the pH in the range of about 9 to about 12, adjacent to an ultrafiltration membrane having a molecular weight cutoff of about 50,000 Daltons, remove the flavoring compounds as permeate, and remove the remaining soy proteins and other soy materials as retained, and (4) neutralize the retained and recover the soy proteins. All types of soy materials are considered potential sources of soy for use in food products. Thus, soy materials containing proteins are combined in an aqueous mixture, usually a suspension of soy solids. The protein content is necessary for food products, but as discussed above, it is believed to contain flavoring compounds that must be released in order to be separated. The separation of flavoring compounds is carried out in an aqueous mixture where both the proteins and the flavoring compounds are dissolved. The concentration of soy materials in the aqueous mixture will be in the range of about 1 to about 20 percent. In general, the concentration of soy materials after pH adjustment will change during the subsequent ultrafiltration step as water is removed with the permeate. The water will be replaced either periodically or continuously.For example, in diafiltration, water is added to gradually dilute the proteins retained in a batch or semi-continuous process. The second step, as will be seen in the examples, is important. If the removal of flavoring compounds is to be achieved, soy proteins are solubilized by adding a base to the aqueous mixture to obtain a pH of about 9 to about 12. Generally, a pH of about 9 has been found to be necessary to solubilize all proteins, while a pH greater than about 12 will likely cause undesirable protein degradation. Although in theory any base can be used, sodium or potassium hydroxide is preferred, particularly potassium hydroxide. Other bases that may have application include calcium, magnesium, and ammonium hydroxides. It is believed that the solubilization of soy proteins changes their shape and somehow results in the release of flavoring compounds, which may be bound or encapsulated by the soy proteins when they are in neutral or acidic solution.The flavoring compounds, which have a relatively low molecular weight compared to soy proteins, are able to pass through the pores of the ultrafiltration membrane, while substantially all the solubilized soy proteins are too large and are retained. Importantly, the pH must be maintained within the range described above (i.e., approximately 9 to approximately 12) during the ultrafiltration / diafiltration process to allow for the removal of as many flavoring compounds as possible. The third step should be carried out in a batch mode similar to the laboratory experiments recorded below in Examples 1-5, where the flavoring compounds and water passed through the membrane and were removed by flowing water. However, in commercial applications of the invention's process, the pH-adjusted aqueous mixture should be continuously circulated adjacent to an ultrafiltration membrane. Because water, caustic, and flavoring compounds pass through the membrane as permeate and are discarded, additional water will be added to maintain the desired concentration of soy materials, which will tend to lower the pH of the aqueous mixture. This water can be increased by removing water from the Permeate and recycle the recovered water to the feed stream. A pH modifying material (e.g., base) can be added, as needed, to control the pH in the desired range (i.e., about 9 to about 12) directly into the ultrafiltration solution, to any recycled aqueous material, or to top-up water, as desired. After removing the flavoring compounds (i.e., after completing the ultrafiltration process), further neutralization of the filtered solution can be achieved by removing the product and adding an acid, as required to reach the desired pH. After pH adjustment, the aqueous mixture of soy proteins and other materials can be used directly in food products, or it can be concentrated or dried as required for the intended use. A process for dearomatizing soy materials by ultrafiltration can be operated in several modes. The pH during the ultrafiltration / diafiltration process is maintained in the range of about 9 to about 12, and preferably in the range of about 9.5 to about 10.5. Two methods will be described: continuous processing and batch processing (including semi-continuous operation). Commercial processes are expected to adopt batch or semi-continuous operation, which should be better suited for the production of food-grade soy products. A continuous process is generally shown in Figure 8.In a continuous or batch process, an aqueous mixture of soy materials is pH-adjusted to solubilize the soy proteins and release the flavoring compounds, and then passed adjacent to an ultrafiltration membrane that allows the lower molecular weight flavoring materials to pass through its pores along with water (the permeate), leaving the higher molecular weight soy materials (the retentate) to be recirculated. A portion of the retentate will be removed as deflavored product, from which soy materials can be recovered as needed for ultimate end use. Water will be added. To replace this loss in the permeate and to provide a constant concentration of soy materials in the feed stream supplied to the ultrafiltration membrane. Although not essential to the process, the process in Figure 8 includes additional processing of the permeate to recover a portion of the water using a reverse osmosis membrane for recycling to combine the retentate and new soy materials. The advantage of this step is to reduce the amount of new water that must be added to the process and removed in the permeate concentration. As is evident, the pH of the soy-derived materials can be maintained within the desired range by appropriate addition of a base to be recycled or new water added to the process or by direct addition of base, as desired. In a batch process, as described in Examples 6-8 below, a batch of soy material is placed in a vessel, the pH adjusted, and fed to an ultrafiltration membrane. The permeate is separated and the retentate is returned to the vessel. As the process progresses, the soy material is exhausted of lower molecular weight flavor compounds and water and becomes more concentrated in the desirable soy proteins. Periodically, water is added to the retentate to dilute it and provide a vehicle for the flavor compounds that are passed through the membrane. In a semi-continuous process, water is added continuously at the rate at which it is being removed in the permeate. The process is continued until all flavor compounds have been removed and the retentate is sufficiently deflavored to become the product, which can then be further processed as required for end use.A batch or semi-continuous process may also include permeate concentration, with separate water recycling in a manner similar to that shown in Figure 8. The pH during the ultrafiltration / diafiltration process is maintained in the range of about 9 to about 12, and preferably in the range of about 9.5 to about 10.5. The ultrafiltration membrane will be operated with a differential. Pressure across the membrane aids the migration of flavoring compounds, water, and other materials that are able to pass through the membrane pores, while not exceeding the membrane's physical resistance. The typical average pressure for these membranes is approximately 345 kPa. The trans-membrane pressure (inverted outwards) will be approximately 103 kPa. As is evident, these pressures can be varied based on membrane specifications and other operational concerns. The feed stream flow rate will provide sufficient residence time for significant permeate removal, but will also be high enough to provide turbulence so that feed stream access to the membrane pores is not impeded by solid deposits on the membrane walls. One skilled in the art will understand that the appropriate operating parameters will be determined by experience with the materials being separated. In a preferred embodiment, the present invention provides a method for preparing deflavored soy protein material, said method comprising (a) preparing an aqueous composition of a soy material containing soluble soy proteins, flavoring compounds and insoluble materials, (b) solubilizing the soy proteins by adjusting the aqueous composition of (a) to a pH in the range of about 9 to about 12 and releasing the flavoring compounds, (c) removing the insoluble materials from the pH-adjusted aqueous composition of (b) to obtain a treated aqueous composition; (d) passing the treated aqueous composition of (c) adjacent to an ultrafiltration membrane having a molecular weight cutoff of up to about 50.000 Daltons, while maintaining the pH in the range of about 9 to about 12, under appropriate ultrafiltration conditions whereby the flavoring compounds pass through the membrane, thus de-flavoring the soy material and retaining substantially all the solubilized soy proteins, and (e) recovering the solubilized soy proteins retained by. Ultrafiltration membrane to obtain dearomatized soy protein material. This preferred embodiment is illustrated in Figure 11, where the pH of an aqueous solution of soy protein is adjusted to about 9 to about 12. The pH-adjusted aqueous solution is then treated to remove insoluble materials. Any conventional technique (e.g., filtration, decantation, centrifugation, and others) can be used. Preferably, the insoluble material is removed by centrifugation. Commercially available continuous centrifugation units are ideally suited for this separation in a continuous or semi-batch operation. In a particularly preferred embodiment, the pH-adjusted aqueous solution is subjected to the removal technique (e.g., centrifugation) at least twice in order to facilitate or more completely remove the insoluble materials.The treated supernatant is then subjected to ultrafiltration, preferably combined with diafiltration, in order to remove the aroma components normally associated with soybeans. During ultrafiltration, the pH of the soy-derived material should be maintained in the range of approximately 9 to approximately 12. After ultrafiltration, the pH is adjusted to a neutral pH using an edible acid (e.g., citric acid). The de-aromatized soy protein solution can be used directly or can be converted into a solid form if desired. Any conventional technique for removing water can be used. Generally, spray drying or freeze-drying techniques are preferred. Deflavored soy protein products. Deflavored soy materials prepared by the present methods are ideally suited for use in dairy and non-dairy beverages, non-sediment fruit drinks of the smoothie type, wellness drinks, cheeses, cheese analogues, dairy and non-dairy yogurts, meat products and Meat analogues, cereals, baked goods, snacks, and others. Unless otherwise indicated, all percentages are expressed by weight. EXAMPLE 1. Soy protein isolate (Protein Technology International (PTI), St. Louis, MO) was hydrated in tap water to provide a 10 percent concentration. The aqueous composition was mixed with a magnetic stirrer until all the soy protein isolate was completely dispersed. The pH of the mixture was adjusted to 11.0 using sodium hydroxide, then the pH-adjusted composition was placed in a dialysis tube (Spectrum Inc.) having a molecular weight pore size of 3500, and tap water was passed over the outside of the tube continuously for approximately 4 h; the pH remained greater than 9 during dialysis. The remaining composition in the dialysis tube was poured into a glass beaker, neutralized, and evaluated for aroma and taste. A comparison was made between the dialyzed composition and a similarly treated sample with a pH of 6.7 and a second sample that was neither dialyzed nor pH-adjusted.A blinded evaluation by several individuals showed that only the pH-adjusted and dialyzed sample had a significantly improved taste and aroma. EXAMPLE 2. A similar test was performed using soy milk (Devansoy Farms, Carroll, Iowa), made in a 10% aqueous composition, then the pH was adjusted and dialyzed overnight as in example 1. After treatment, the sample pH was 8.8 and the aroma and flavor were significantly improved. EXAMPLE 3. Example 2 was repeated with freshly prepared soy milk by soaking and blanching the beans and then grinding and separating the soy milk from the flour. After pH adjustment and dialysis as previously described, the taste and aroma of the soy milk were found to be significantly improved. EXAMPLE 4. Example 3 was repeated using the tube of Dialysis with a molecular weight pore size of 6000 yielded similar results. EXAMPLE 5. Example 3 was repeated with soy flour powder (Cargill). The soy flour was hydrated to a 10 percent composition and then the pH adjusted as previously described. After overnight dialysis, the pH of the remaining composition in the dialysis tube was 8.7 and had a significantly improved aroma and taste. EXAMPLE 6. In a large mixing tank, 15 kg of Sun Rich soy milk containing 15 percent solids were diluted with 30 kg of water to produce a 45 kg suspension containing 5% soy solids. A solution of IN NaOH was slowly added to solubilize the soy proteins until a pH of 11 was reached. A diafiltration of an alkalized soybean solution was performed by pumping the solution from the mixing tank through two parallel hollow fiber membranes (A / G Technology Corporation) having a molecular weight cutoff of 10,000 Daltons and a surface area of ​​3.3 m². 2The trans-membrane pressure across the membrane was 138–345 kPa. The material that passed through the membrane (permeate) was collected. The remaining material (retained) was continuously recycled to the mixing tank. When 22.7 kg of permeate had been collected, the mixing tank contained 22.7 kg of soybean solution. An additional 22.7 kg of water was added to the mixing tank. The pH was maintained at approximately 9 to approximately 12 during ultrafiltration / diafiltration. This washing with the addition of water to the mixing tank was repeated five times, after which the solution in the mixing tank was concentrated to approximately 10 percent solids as water was removed from the permeate, and then the retained soybean solution was neutralized with 2 percent citric acid to a pH of 7.0. The neutralized solution was evaluated by a trained sensory panel and compared to a control sample of Run Rich soy milk. which had been diluted to 10 percent with water, but not otherwise treated. The soybean solutions were presented in a blinded, randomized order. The results are shown in the graphs in Figures 1 and 2. Figure 1 shows the intensity score for 10 attributes. The panel judged some attributes to be more significant than others. When compared to the soybean solution that had been treated as described above, the surprising attributes had all been reduced with a 95 percent confidence level. Those attributes that are less prominent in the control (i.e., Dark, Sweet, Sour, Salty, and Bitter) were reduced, except for Sweet, which increased in value, but the panel's average values ​​did not reach a 95 percent confidence level. It is evident from the results that the soy solution was made more neutral in aroma by removing the aroma components. EXAMPLE 7 - 4.55 kg of soy protein concentrate (Central Soya) were mixed with 86.4 kg of water in a tank with high agitation for 15-30 min to hydrate the soy protein, then 1 N NaOH was added to solubilize the soy protein to a pH of 11. In a similar manner to that described in Example 6, the soy suspension was pumped through a spiral membrane (Gea Niro Inc.) having a molecular weight cutoff of 10,000 Daltons. The trans-membrane pressure across the membrane was maintained below 344.7 kPa. The pressure drop across the membrane was maintained below 103.4 kPa, and the pH was maintained at approximately 9 to approximately 12. As in Example 6, five additions of water were made when the permeate removed from the membrane reached half the original volume in the mixing tank. After five additions of water, the pH of the washed soybean solution was adjusted to 7.5 by adding 0.5 N HCl, and then freeze-dried for sensory evaluation. Unflavored soy protein concentrate was evaluated for six attributes by a trained sensory panel. The average values ​​for Each attribute for the control (untreated) sample is given in Figure 3. In this example, a difference was found between the deflavored soy concentrate and the control, but none were at a 95 percent confidence level, although all values ​​were lower. This is shown in Figure 4. Also included are the results of a blind control used, which was rated after the deflavored sample. In this case, the blind control was found to have stronger aroma attributes than the original control in Figure 3. It is believed that this occurred because the blind control in this example was tested after the deflavored sample and appeared to the panel to have a relatively stronger aroma in the second evaluation of the control. However, when compared to the blind control sample, the deflavored sample showed significant differences for three of the aroma attributes at the 90-95 percent confidence level, as shown in Figure 5. EXAMPLE 8. The membrane used to dearomatize soy proteins must have a molecular weight cutoff of 10,000 Daltons, demonstrated to be effective in Examples 6 and 7. A higher molecular weight membrane could be used if desired, but at a molecular weight cutoff of 50,000 Daltons, some valuable proteins were lost in the permeate, as shown in this example. 2.27 kg of a powdered soy isolate (Supro-670 PTI) were mixed with 43.2 kg of water as in Example 7 to provide a suspension containing 5% soy solids. 1 N NaOH was added to raise the pH to 11 and solubilize the soy proteins. Diafiltration using the five water additions was performed in a similar manner to that described in Examples 6 and 7 and using the hollow fiber membranes of Example 6. The pH was maintained at approximately 9 to approximately 12 during ultrafiltration / diafiltration. Permeate samples were taken at five-minute intervals, neutralized, and frozen for protein analysis. The permeate samples were analyzed for protein content. total by electrophoresis, with the results shown in the following table: TABLE A Time (min) Molecular weight cutoff 10000 Daltons 50000 Daltons Protein (%) Protein (%) 0 0 0.4 5 0.6 1 10 0.8 0.6 15 0.4 0.6 20 0.4 0.6 25 0 0.4 30 0 0.4 35 0.5 0.4 40 0 ​​0.3 45 0 N / A It can be noted that the membrane having a 10,000 cut Daltons retain more protein than the membrane, having a cutoff of 50,000 Daltons. The value at 35 min for the membrane of 10,000 Daltons is erroneous, as is commonly believed. EXAMPLE 9. Samples of dearomatized soy materials using the methods of Examples 6-8 were analyzed by protein gel electrophoresis. The results indicate that the molecular weight distribution of the retained soy materials was substantially the same as that of the dearomatized soy material. The results are shown in the following table. TABLE B Molecular Weight (kD) Soy Material Soy Flavor Soy Isolate Soy Isolate Soy Milk control (%) deflavored (%) control (%) deflavored (%) control (%) deflavored (%) control (%) deflavored (%) >26 74 73 21.7 19.7 22 20 69 71 14-27 18 19 30.8 32.2 31 32 20 21 3.5-14 7 8 47.4 48 45 48 10 9 <3.5 0 0 0 0 0 0 0 0 EXAMPLE 10. Analyses were performed for the chemical constituents associated with the aroma attributes determined by the sensory panels described in the previous examples. Two samples of soy protein isolates were tested. One sample was deflavored using the method described in Example 7, the second sample was not deflavored. In the first test, one gram of a control sample was diluted with 15 g of water, 2 pl of 300 ppm 4-heptanone were added as an internal standard, and the mixture was purged with 100 ml / min of helium at 60°C for 30 min. A deflavored sample was prepared similarly to the control sample, except that the pH was raised to 10 by adding a NaOH solution in order to solubilize the proteins. Volatile compounds were analyzed by GC / MS (HP GC 5890 / MSD5972). The results for the various compounds are shown in Figures 6 and 7. The deflavored soy sample contained smaller amounts of flavoring compounds. In a second test, three-gram samples were diluted with 30 g of water, and 2 p.1 of 300 ppm 4-heptanone were added as an internal standard. The resulting mixtures were purged with 100 ml / min of helium at 60°C for 20 min to remove volatile compounds. The volatiles were analyzed by gas chromatography, and the odor of the compounds was judged by human criteria. The odors associated with specific chemical compounds are reported in the following table: TABLE C. Odor characteristics of reduced compounds after the process deodorizing. Compound Odor in SPI control Odor in dearomatized SPI 1-pentanol Weak, green Slightly greasy 2-ethylphenol Temperate, herbaceous ND 1-nitropentane ND ND l-octen-3-ol Mushroom, earthy taste, very strong Mushroom, earthy taste, strong Cis-2,4-heptadienal ND ND Cis-3-octen-2-one ND ND Trans-2,4-heptadienal ND Weak green Acetophenone Burnt, floral, caramel Burnt, caramel Cis,trans-3,5-octadien-2-one ND ND Trans,trans-3,5-octadien-2-one Green, floral, greasy Greasy, green 2,4-nonadienal Greasy, oily, deep toasted Greasy, oily, deep toasted Cis-2,4-decadienal Greasy, Oily, moldy Green onion, stained with ink 4-(1-methylpropyl)phenol Chewing gum, fruity ND Trans-2,4-decadienal Fatty, oily, waxy Fatty, oily, green 2-pentylfuran Green, floral, ethereal Green, floral, ethereal Trans-3-octen-2-one Floral, green, earthy-tasting floral EXAMPLE 11. The application of soy materials to food products was illustrated by adding deflavored soy material to a Balance Bar® (Kraft Foods), and comparing the aroma with an equivalent Balance Bar® containing the same soy material that was not deflavored. In one sample, all the soy material was a powdered soy isolate (PTI's Supro-661); in the second sample, 50 percent of the soy material was deflavored by the diafiltration process of the examples, and 50 percent was not deflavored. A taste panel preferred the second sample 8 to 3, rating it 6.11 on a scale of 1-10 (with 10 being the best), versus a score of 3.5 for the first sample. EXAMPLE 12. In a manner similar to example 6, samples of soy isolate were compared, dearomatized according to the process of the invention, and the control sample of concentrated soy isolate. The protein content was hydrated in water to a 10 percent solution. Figure 9 shows the results found by a trained sensory panel for the control sample. The descented sample was compared with the control by the panel, and it was verified, as noted in Figure 10, that many of the characteristic attributes of the control sample had been reduced. However, it was found that the designated oxidized aroma had increased. EXAMPLE 13 Defatted soybean meal (13.5 kg: Archer Midland Daniels (AMD), Decatur, Illinois) was hydrated with water (121.5 kg) in a jacketed mixing tank with vigorous mixing at a temperature of approximately 54.4°C. Once hydration was complete (generally in about 15 min), the pH was adjusted to 10 using 1 N NaOH (approximately 6.75 kg added). The pH-adjusted solution was mixed for about 30 to about 45 min at about 54.4°C. The resulting suspension was pumped through a continuous centrifuge (Westfalia Separator Inc., Northvale, NJ) at about 54.4°C and 12,000 rpm. The supernatant and insoluble sludge were continuously collected as separate streams. The collected supernatant was passed through a continuous centrifuge a second time under similar conditions to further remove insoluble material. The twice-centrifuged supernatant was then diafiltered through an ultrafiltration membrane (spiral-wound type with 10.000 molecular weight cutoff). Diafiltration was continued for the equivalent of 5 washing cycles (each wash defined as the amount of permeate collected equal to half the initial batch size). The pH was maintained at approximately 10 during optional ultrafiltration / diafiltration. Once diafiltration was complete, citric acid (1%) was added to adjust the pH to 6.5. The resulting suspension was concentrated by ultrafiltration to approximately 10 to approximately 15 percent solids, pasteurized, and then spray-dried. EXAMPLE 14. This example compares soybean material. Deflavored product prepared by the method of this invention with similar materials prepared from prior art processes (i.e., U.S. Patent 4,420,425 (issued December 14, 1963) and U.S. Patent Application Publication 2002 / 0098276 (published July 25, 2002)). In each process, a defatted soy flour (Cargill, Inc.) was used as the starting material. Inventive Process. Defatted soy flour (13.5 kg) was hydrated in 121.5 kg of water at 50°C. IN NaOH solution was slowly added to the soy suspension to adjust the pH to 10.0. Soy protein extraction was performed for approximately 30 min at 50°C. At the end of the extraction, the suspension was centrifuged at 12000 G using a Westfalia continuous separator (Model SC-6) with continuous sludge removal of spent material and a feed rate of approximately 300 L / hour. The supernatant was collected and re-centrifuged. The extracted protein suspension was then diafiltered through a UF membrane with a molecular weight cutoff of 10,000 Daltons at approximately 50°C; the retentate was recirculated and water was added at the same permeate removal rate. The pH was maintained at 10.0 for the duration of the diafiltration. Diafiltration continued until the collected permeate was equal to 2.5 times the initial batch volume (i.e., 5 washes).Once diafiltration was complete, the retentate was concentrated to 10 percent solids and the pH adjusted to 6.5 with 1 percent citric acid. The product was then collected and spray-dried. Comparative Process 1. (based on US Patent 4,420,425). Defatted soybean flour (13.5 kg) was hydrated in 121.5 kg of water at room temperature. IN NaOH solution was slowly added to the soybean suspension to adjust the pH to 9.0. Soy protein extraction was performed for 40 min at 55°C. At the end of the extraction, the suspension was centrifuged at 12,000 G using a Westfalia continuous separator (model SC-6) with continuous sludge removal of spent material and A feed rate of approximately 300 L / hour was used. The supernatant was collected and re-centrifuged. After a second centrifugation, the pH had dropped to 7.5. The extracted protein suspension was then diafiltered through an ultrafiltration membrane with a molecular weight cutoff of 30,000 Daltons at approximately 50°C; the retentate was recirculated and water was added at the same permeate removal rate. The pH was not controlled during diafiltration and had dropped to 7.0 upon completion of diafiltration. Diafiltration continued until the collected permeate equaled 2.5 times the starting batch volume (i.e., 5 washes). Once diafiltration was complete, the retentate was concentrated to 10 percent solids and the pH adjusted to 6.5 with 1 percent citric acid. The product was then collected and spray-dried. Comparative Process 2 (based on US Patent Application Publication 2002 / 0098276). Defatted soybean flour (13.5 kg) was hydrated in 121.5 kg of water at 25°C. IN NaOH solution was slowly added to the soybean suspension to adjust the pH to 9.0. Soy protein extraction was performed for approximately 30 min. At the end of the extraction, the suspension was centrifuged at 12000 G using a Westfalia continuous separator (Model SC-6) with continuous sludge removal of spent material and a feed rate of approximately 300 L / hour. The supernatant was collected and re-centrifuged. After the second centrifugation, the pH had dropped to 8.0. The extracted protein suspension was then diafiltered through an ultrafiltration membrane with a molecular weight cutoff of 10,000 Daltons at approximately 25°C; The retentate was recirculated and water was added at the same permeate removal rate. The pH was not controlled during diafiltration and had dropped to 7.5 by the time diafiltration was complete.Diafiltration continued until the collected permeate equaled 2.5 times the initial batch volume (i.e., 5 washes). Once diafiltration was complete, the retentate was concentrated to 10 percent solids and the pH adjusted to 6.5 with 1 percent citric acid. The product was then collected and spray-dried. The deflavored soybean material obtained from each of the processes was evaluated. The taste was assessed using a trained panel. Although each of the samples was acceptable (i.e., appropriate reduction of the soybean aroma profile), the inventive product has the best overall aroma profile. The functional properties (e.g., solubility, water retention, and others) were also determined; the results are presented in the table below: Sample Particle size (µm) Solubility Water retention (g water / g protein) % nitrogen solubility index Inventive Process 20.2 62.4 93.0 6.1 Comparative Process 1 115.7 59.9 77.9 3.8 Comparative Process 2 44.6 14.5 22.7 4.9 Especially for use in low-fat food products. For viscosity (e.g., beverages, salad dressings, and others), it is especially important that solubility be high and the average particle size small in order to provide a good mouthfeel and taste. Low solubility results in sediment formation and a gritty mouthfeel; larger particles also result in an undesirable gritty and / or chalky mouthfeel. The particle size of the material produced by the inventive process was significantly smaller than that of materials prepared from one of the other processes. The particle microstructure was also examined using microscopy. The material from the inventive process was transparent with relatively thin walls. The material produced from comparative process 1 had both thin and thick walls, while the material produced from comparative process 2 had thick walls. Thin-walled particles tend to be lighter than thick-walled particles and will thus tend to form a suspension more easily and remain in suspension longer. thus providing a better mouthfeel when incorporated into food products. The inventive process provided deflavored soy materials with significantly higher solubility and water retention than either of the two comparative processes.

Claims

CLAIMS 1. Method for preparing deflavored soy protein material, characterized by the fact that it comprises: (a) prepare an aqueous composition of a soy material containing soluble soy proteins, flavoring compounds and insoluble materials, (b) to solubilize the soy proteins by adjusting the aqueous composition of (a) to a pH in the range of about 9 to about 12 and releasing the flavoring compounds, (c) remove insoluble materials from the pH-adjusted aqueous composition of (b) to obtain a treated aqueous composition; (d) passing the treated aqueous composition of (c) adjacent to an ultrafiltration membrane having a molecular weight cutoff of up to about 50,000 Daltons, while maintaining the pH in the range of about 9 to about 12, under appropriate ultrafiltration conditions whereby the flavoring compounds pass through the membrane, thus deflavothing the soy material and retaining substantially all solubilized soy proteins, and (e) recover the solubilized soy proteins retained by the ultrafiltration membrane to obtain the dearomatized soy protein material. for the 2. Method according to claim 1, characterized in that the soy material is at least one member of the group consisting of soy milk, soy protein isolate, soy concentrate, and soy flour.

3. Method according to claim 1, characterized by the fact that the soybean material is soybean flour.

4. Method according to claim 3, characterized by the fact that the soy flour is defatted soy flour.

5. Method according to claim 2, characterized for the for the The fact that insoluble materials are removed from the pH-adjusted aqueous composition using at least one centrifugation step.

6. Method according to claim 4, characterized in that the insoluble materials are removed from the pH-adjusted aqueous composition using at least one centrifugation step.

7. Method according to claim 5, characterized in that the aqueous composition of (a) has a concentration of soy material in the range of about 1 to about 20 percent.

8. Method according to claim 6, characterized in that the aqueous composition of (a) has a concentration of soybean material in the range of about 1 to about 20 percent.

9. Method according to claim 5, characterized in that the ultrafiltration membrane has a cutoff in the range of about 1,000 to about 50,000 Daltons.

10. Method according to claim 6, characterized in that the ultrafiltration membrane has a cutoff in the range of about 1,000 to about 50,000 Daltons.

11. Method according to claim 9, characterized in that the ultrafiltration membrane has a cutoff in the range of about 10,000 to about 30,000 Daltons.

12. Method according to claim 10, characterized in that the ultrafiltration membrane has a cutoff in the range of about 10,000 to about 30,000 Daltons.

13. Method according to claim 11, characterized in that the ultrafiltration is carried out at a temperature in the range of about 10 to about 60°C and at an appropriate pressure.

14. Method according to claim 12, characterized in that the ultrafiltration is carried out at a temperature in the range of about 10 to about 60°C and an appropriate pressure.

15. Method according to claim 13, characterized in that the ultrafiltration membrane is a polymer, ceramic or inorganic membrane.

16. Method according to claim 14, characterized in that the ultrafiltration membrane is a polymer, ceramic or inorganic membrane.

17. Method according to claim 1, characterized in that the deflavored soy protein material is further treated to remove water to obtain a solid deflavored soy protein material.

18. Method according to claim 5, characterized in that the deflavored soy protein material is further treated to remove water in order to obtain the deflavored soy protein material in solid form.

19. Method according to claim 6, characterized in that the deflavored soy protein material is further treated to remove water in order to obtain the deflavored soy protein material in a solid form.

20. Method according to claim 1, characterized in that the deflavored soy protein material is spray-dried to remove water in order to obtain the deflavored soy protein material in a solid form.

21. Method according to claim 5, characterized in that the deflavored soy protein material is spray-dried to remove water in order to obtain the deflavored soy protein material in a solid form.

22. Method according to claim 6, characterized in that the deflavored soy protein material is spray-dried to remove water in order to obtain the deflavored soy protein material in a solid form.