Processing and product characteristics for textured soy flours,concentrates and isolates

During the last 25 years, the development of processes to provide textural properties in soy proteins has greatly increased the market potential for soy protein products. Many different processes based on soy flour, concentrates and isolates have been developed. They have ranged from products to be used in extension of meats to meat analogs themselves. The real success of new processes is measured by their success in the commercial marketplace. The most successful products have been based on thermoplastic extrusion of soy flour. More recently, second generation products made by the thermoplastic extrusion of soy protein concentrates have been introduced. These products have less flavor, wider variety of functional characteristics and greatly reduced flatulence characteristics compared to textured soy flour products. This paper describes processes used to texturize soy proteins and characteristics of the various products. Product characteristics, functionally and economics are key factors in deciding which product to use in end-product formulations. The wide variety of textured soy proteins available provides a product for each individual need.     

Comparative functionality of soy proteins used in commercial meat food products

The use of soy isolates, concentrates, and texturized flours in meat food products is discussed. Functional characteristics of soy products in relation to their market application are reviewed. Soy isolates find more limited usage in meat food systems (2%) than the concentrates and textured soy flours (8–12%). In weak meat systems containing large amounts of fat (30–45%), the concentrate emulsifier and isolate are more important than the texturized soy flour. In chopped meat systems with 18–25% fat, the textural properties of soy flour (extruded) are more important than the use of an isolate. However, combinations of concentrate emulsifier and texturized flour are used. The method of cooking, i.e. fresh, deep fat-fried, or char-broiled, will affect the usage of soy combinations. In comminuted cooked cured meat food mixes, soy concentrates, and textured flours currently are being used. Nutritional properties are improved by inclusion of available ingredients high in lysine and methionine. Functional measurements of textural properties have been completed using the Instron with a Lee Kramer cell. Both model emulsion systems and finished product results substantiate the accuracy of textural properties in soy-meat mixes using the Instron.     

Protein solubility characteristics of commercial soy protein products

Solubility characteristics of commerical soy protein products (flours, concentrates, and isolates) were determined under various conditions. From the solubility profiles at various pH values and NaCl concentrations, soy protein isolates can be divided into three groups. One group had high solubility near the pl. Another group had low solubility near the pl, but high solubility at pH 11. The third group had low solubility even at pH 11. Except for the hydrolyzed products, the protein solubilities of the soy protein products at various salt concentrations were very low. Temperature did not significantly affect the protein solubility, although a few products showed more than a 20% increase at temperatures >50°C. Soy protein concentrates and soy protein isolates showed similar solubility profiles. The proteins in all commercial products (except flours) tested were denatured, as evident from the solubility profiles in the presence of salt and the enthalpy values from DSC.     

Meat and vegetable protein blends for engineered foods

The meat industry in the United States offers the biggest volume potential for vegetable protein. American Meat Institute reports a 1977 tonnage of 4,377,937,031 pounds of sausage products. Our research with various protein sources is discussed. Emphasis is placed on soy protein products currently available and approved by government agencies. Formulations and requirements for satisfactory products is outlined with economic justifications for soy flour, concentrates and isolates. A thorough discussion of extruded and/or engineered foods is presented showing utilization of mechanically deboned meats, recovered meat proteins from pork and beef rendering, and vegetable proteins in combination with beef and pork. The nutritive values of mechanically deboned chicken and structured soy protein gave PERs over 3.0 with good amino acid balance.     

Phosphorus flow in production of soy protein concentrate and isolate from defatted soybean flour

Implications of excess phosphorus (P) in waste streams obtained from soy-based protein preparation processes on the environment and their potential utilization as P-source are two significant understudied areas. Soybean-based protein ingredients for food products retain comparatively enhanced functional properties and are cheaper than other plant-based proteins. Soybean protein can be extracted and utilized as a food ingredient primarily by preparing soy protein concentrates (SPC) and soy protein isolates (SPI) from soybean meal/defatted soy flour (DSF). In a typical soybean processing facility, along with the soy products and soy-protein preparations, the recovery of phosphorus as a coproduct will enhance the economic feasibility of the overall process as the recovered P can be used as fertilizer. In this study, the SPC and SPI were prepared from the DSF following widely used conventional protocols and P flow in these processes was tracked. In SPC production, ~59% of the total P was retained with SPC and ~34% was in the aqueous waste streams. For SPI process ~24% of total P was retained with SPI and ~59% went in the waste solid residue (~40%) and aqueous streams (~19%). About 80%–89% P removal from the waste aqueous streams was achieved by Ca-phytate precipitation. This work demonstrated that in the process of SPC and SPI preparation the phosphorus from the waste aqueous streams can be precipitated out to avoid subsequent eutrophication and the waste solid residue with ~40% P can be reused as a P-fertilizer as other applications of this residue are unspecified.     

Preparation of soy protein concentrate and isolate from extruded-expelled soybean meals

Soy protein concentrates (SPC) and soy protein isolates (SPI) were produced from hexane-defatted soy white flakes and from two extruded-expelled (EE) soy protein meals with different degrees of protein denaturation. Processing characteristics, such as yield and protein content, and the key protein functional properties of the products were investigated. Both acid-and alcohol-washed SPC from the two EE meals had higher yields but lower protein contents than that from white flakes. Generally, SPC from an acid wash had much better functional properties than those from an alcohol wash. The SPI yield was highly proportional to the protein dispersibility index (PDI) of the starting material, so the EE meal with lower PDI had lower SPI recovery. The protein content in SPI prepared from EE meals was about 80%, which was lower than from white flakes. Nevertheless, SPI from EE meals showed functional properties similar to or better than those from white flakes. The low protein contents in SPC and SPI made from EE meals were mainly due to the presence of residual oil in the final products. SPI made from EE meals had higher concentration of glycinin relative to β-conglycinin than that from white flakes.     

Pea and lentil protein extraction and functionality

These studies have demonstrated that peas and lentils can be used as protein sources for flours, concentrates and isolates. Less research attention has been devoted to lentil protein extraction, probably because of the greater cost of lentils as compared to peas. Pin-milling and air classification is well adapted to extracting pea flours to produce pea protein concentrates. Apparently, air-classification can be applied successfully to starch rich legumes, but will not give satisfactory results with lipid rich legumes. Wet processes, including alkaline and salt and acid solubilization, together with isoelectric precipitation or ultrafiltration, have been developed. The pea and lentil protein extracts of these processes exhibit comparable and complementary functionality to homologous soybean products. Air-classified pea protein concentrates are different from soy protein concentrates because of residual starch which can be useful for particular functional applications. Pea isolates appear to exhibit better foaming properties and more solubility than soy isolates, but pea isolates have to be more concentrated than soy isolates to produce viscous dispersions. The economic feasibility of pea and lentil protein extracts is related directly to protein content of the flour, unique functionality of the extracts, marketability of the by-products of extraction and the cost of peas or lentils. Presented at the 78th American Oil Chemists' Society Annual Meeting, May 17–21, 1987, New Orleans, LA.     

Use of soy proteins in baked foods

Technology for the utilization of soy products in bakery foods is well established and reasonably simple. We can expect the functional properties and flavor of soy products to be continually improved through major research efforts in the soy industry. Large scale protein fortification programs will be forthcoming as the world population continues to grow, and economics dictate more and more efficient sources of nutrients. Before this will be realized, however, careful evaluations of the nutritional requirements and the technical, economic and political situations in a country will have to be made and the constraints removed before widespread use of fortified bakery foods in the commercial sector can be realized. In developed as well as developing countries, the near term constraints for usage of soy proteins in bakery products are represented by food regulations or laws which must be changed before the full nutritional and functional assets of soy proteins can be realized to the benefit of the baking industry.     

Oilseed protein concentrates and isolates

Much attention has been focused on the oilseed crops as an alternate and largely untapped source of food protein in an endeavor to provide needed nourishment for large segments of the world’s expanding population. A significant part of this attention has been devoted to the practical concentration and isolation of the proteins of several oilseeds. As a result of intensive effort during the last decade, soy protein concentrates and isolates are now commercial commodities which are gaining increasing acceptance as useful functional and nutritional ingredients for food. This report is concerned with a brief review of the commercial processing, product characteristics and food utilization of soy protein concentrates and isolates. In addition, pertinent comments on the concentrates and isolates of other oilseed are included. One of 21 papers presented at the Symposium, “Oilseed Processors Challenged by World Protein Need,” ISF-AOCS World Congress, Chicago, September 1970.     

Functional properties of soybean and lupin protein concentrates produced by ultrafiltration-diafiltration

Ultrafiltration followed by diafiltration (UF-DF) was evaluated for the production of protein products from partially defatted soybean meal or undefatted lupin (Lupinus albus L.2043N) meal. This study determined the effects of UF-DF on functional properties of the extracted proteins and compared the results with those of protein prepared by acid-precipitation (AP). UF-DF produced only protein concentrates (73% crude protein, dry basis, db), while AP produced protein isolates (about 90% crude protein, db). Soybean protein produced by UF-DF showed markedly higher values for solubilities up to pH 7.0, surface hydrophobicity index, emulsion activity index, and foaming capacity than did the AP soybean protein. UF-DF soy protein was also the most heat-stable among all protein samples tested. With lupin proteins, only the surface hydrophobicity and emulsion activity indices were significantly improved by using UF-DF. UF-DF generally had no adverse effects on, and in most cases even improved, the functional properties of soy protein concentrate produced by this method. UF-DF did not produce a comparable improvement in functional properties of lupin proteins as it did for soybean protein.     

Retorted meat and vegetable protein combinations

Soy proteins are the most versatile, widely used and accepted of the vegetable proteins. Flours and grits are not often used in retorted products because of their flavor. Textured flours are limited in their applications because of the intensification of their beany flavor and their loss of structure on retorting. Concentrates have an improved flavor profile, but relatively low functional properties, and are used as protein supplements and water and fat absorbers in some retorted products. Structured concentrates have a bland flavor profile and retain their good flavor and texture on sterilization and are well suited to a variety of retorted products. When high levels of extension with structured concentrates are used, adjustments may be necessary to increase the binding properties of the mass. The binding, gelling and emulsifying properties of soy protein isolates are particularly useful in retorted products since these properties are maintained at sterilizing temperatures. Novel methods of augmenting or dilating meat products using isolate-salt-polyphosphate brines are outlined, including the preparation of restructured meats. The use of textured proteins and isolates in the preparation of reformed or restructured meats is also described.     

Technical problems and opportunities in using vegetable proteins in dairy products

The food processing industry is giving increased emphasis to the production and utilization of alternate protein isolate products as functional and nutritional ingredients in an expanding number of formulated food products. Alternate protein sources such as soy and other vegetable proteins offer additional flexibility in formulating foods due to their economics, availability, functionality and nutritional properties. This paper discusses needs for developing soy and vegetable protein isolates with improved flavor, color and functionality for producing simulated dairy foods. It also considers alternative technologies for incorporating soy and vegetable proteins into the formulation so that they may function properly for forming stable solutions, emulsions, foams and gels that resemble those in their natural dairy food counterparts.     

Designing vegetable proteins to fit market needs

The needs and wants of the market are discussed as well as the regulatory practices that frequently inhibit the fulfillment of the market’s requirements. The advantages and short comings of the various types of protein ingredients are described, and appeals are made to the soy protein-producing industry to protect the integrity of traditional products by recommending extension of meat and other products in such a manner as to preserve their traditional character. Improved technical service offered to the food processors can bring added assurance to the consumer of a continuing supply of quality traditional products. The soy protein industry must continue the development of their own products so that broader application is possible. The inherent nutritional and functional values of soy proteins are such as to make a new generation of textured products, and improvement in the functional properties of concentrates and isolates a very realistic goal. Compatibilities of soy proteins with other proteins and ingredients are discussed; suggestions are made that the inherent synergism in many of these combinations is an untapped developmental area that will enable us to design protein ingredients for specific applications and thus benefit the consuming public, as well as the food processing industry.     

Foaming properties of soybean protein-based plywood adhesives

A study was conducted to evaluate the potential of soy protein-based plywood glues for foam extrusion. Foaming properties were the first criterion used to screen several soy protein sources. Foaming capacities and stabilities of glue mixes containing animal blood (control) or soy products (meals, flours, concentrates, and isolates) were compared and correlated with molecular weights and surface hydrophobicity indices (S _o) in an attempt to identify structure/function relationships. The blood-based glue mix produced more foam than any of the soy-based glues. Soy flours and concentrates generally produced greater foam volumes and more stable foams than soy meal and isolates. Differences in foaming properties could not be explained by solubility profiles or S _o. However, results of gel electrophoresis indicated that soy products with poor foaming properties had extensive structure modifications or contained considerably lesser amounts of protein available for foaming reactions. Glue mixes containing the soy flours ISU-CCUR, Honeysoy 90, Nutrisoy 7B, and defatted Soyafluff and the soy concentrates Arcon F, ISU-CCUR, and Procon 2000 demonstrated the desired mixing and foaming properties for foam extrusion.     

Future developments in soy protein research and technology

The many successful and desirable uses of soy products have been recounted in the talks during the past three days. We will attempt to emphasize: (A.) That practically every natural food can be improved in its adaptation to food for man. This includes milk. Improvement may be made by deleting certain undesirable factors such as flavors, odor, or anti-nutritional factors. We will attempt to point out that many of these undesirable factors have been recognized and either eliminated or reduced to insignificance. We also will point out that further improvement may be made by enhancing functional and nutritional characteristics; (B.) That acceptance of soybean products as desired food constituents can result in further improvement in both yield and quality of the basic product as well as of the flours, concentrates, and isolates, which in turn may result in more economical production and processing costs; (C.) That the best progress is accomplished by those who recognize the inherent problems in the products and who are honestly willing to do something about them. It is the responsibility of every processor of food products, in the U.S. and elsewhere, to produce food products worthy of the quality of the raw product from which they are produced. This is particularly true of soybeans. The observance of all these factors will result in a real contribution to the food industry throughout the world.     

Vegetable protein application in whey soy drink mix and ice cream

Full fat and defatted soy flours have been used successfully as major ingredients in a low cost replacement for milk solids in beverages for human consumption in several countries of the world. Milk solids replacement products using vegetable protein may have limited potential as long as surplus milk solids exist on a world basis. Some of the milk trends that are occurring in the U.S. are discussed as they pertain to future use of vegetable protein. It appears likely that there will be a decline in milk production with a higher per capita disposable income available for the purchase of processed dairy products utilizing vegetable protein. Ice cream is one of the more sensitive test systems in which to evaluate the flavor and functional properties of vegetable protein for use in dairy products. Sensory panel data have shown that properly processed soybean isolate protein can be used as a 50% replacement for milk solids protein with no discernible differences from a control product. These sensory tests in ice cream show significant differences among commercial soy isolates.     

Soy flour and grits for use in food products

Processing alternatives enable the soybean processor to manufacture soy flour products which vary in fat content, granulation and degree of heat treatment. By controlling these variables, the processor is able to regulate the nutritional value and functional properties of these products. The application of soy flour products is dependent upon their functional properties, nutritional value and low cost. Currently, the major markets for soy flour and grits are in pet foods and animal feeds, cereal based foods and ingredients, meat based foods, and as a substrate for refined protein products such as the textured vegetable proteins, soy protein concentrates, isolates and hydrolysates. These soy protein products are generally marketed as functional and nutritional substitutes for meat, milk and egg protein. For example, soy flour is a functional replacement for milk in many cereal-based foods, e.g., bread, and also enhances the nutritional value of the cereal protein by supplying lysine to the formulation. The United States government has pioneered the development and marketing of protein-enriched, cereal-based foods designed to combat worldwide starvation. The government has directly supported the research and development of corn and wheat-based food substrates supplemented with soy flour, and has purchased over one billion pounds of these products since 1966 for worldwide distribution. One of 21 papers presented at the Symposium, “Oilseed Processors Challenged by World Protein Need,” ISF-AOCS World Congress, Chicago, September 1970.     

Soy protein products and their production

The soybean industry in the U.S. started in the first years of this century and was only 5,000,000 bushels just 50 years ago. This year it is expected to be over 1.5 billion bushels, reflecting a remarkable growth. Beans are processed primarily for soybean oil and for meal to be used in poultry and livestock feeds. Only ca. 3% soy protein is used in human food today. Special processing is required to prepare proteins to meet the various specifications of products for the food industry. Methods used to produce flour and grits, spun fibers, textured proteins, concentrates, and isolates are described.     

Technische Probleme und Lösungen bei der Gewinnung von Sojaproteinen

Technical Problems and Solutions in the Recovery of Soy Proteins Soy proteins are interesting as food ingredients for economic and technical reasons. High yields per hectare, easy availability, low transport- and storage costs and low processing costs are favourable economic factors. The technical i. e. nutritional, functional and organoleptic properties influence each other. To optimize these properties for the specific applications, the proteins should be refined. The non-refined soy protein products i. e. defatted flour and textured flour have limited application. However the refined products i. e. concentrates, isolates and their textured forms, offer far better possibilities for the food industry.     

Effects of consumption of processed soy proteins on minerals and digestion in man

Most of our knowledge of digestion and utilization of minerals and other components of foods is derived from model experiments with animals. Results indicate that digestion and utilization depend not only on type of foodstuff, but also on, e.g., animal species, nutritional status and overall diet composition. Despite these limitations, such model experiments help us in delineating problem areas and in finding solutions. To verify the conclusions drawn, tests in human beings, preferably under normal living conditions, are needed. Results of animal experiments with soy protein materials indicate that no major effects from the consumption of heat-treated soy proteins are to be expected. As systematic human experiments are scarce, we carried out a large scale experiment to assess acceptation and the possible physiological effects of substituting soy proteins for conventional proteins in the usual diet. We compared two diets in a 4+4 week crossover design with 92 healthy volunteers. One diet contained a wide variety of soy protein foods, mainly made with concentrates (test diet), about 25% of the protein intake being from soy. The other diet (control) contained products made from conventional protein sources. Although most of the 100 parameters investigated showed no difference, statistically significant reactions to soy were observed in mineral metabolism and digestion. All these changes are well within normal physiological ranges, do not indicate unfavorable trends, and can be explained by adaptation to shifts in dietary composition due to substitution of soy protein materials for conventional protein sources. In a separate experiment with 12 subjects, the effect of processing soy proteins on flatulence was investigated. It was found that refining can remove up to two-thirds of the oligosaccharides stachyose and raffinose, with a parallel decrease in volume of intestinal gas production. We conclude that these results confirm the prevailing view that soy protein materials are acceptable for our daily food.