The role of soybeans in food systems

Technological advances have made it possible to have soybean protein available in various forms: as whole seeds and flours, protein concentrates and protein isolates. These products differ in functional properties as well as in fat and protein content; however, amino acid patterns on a protein basis are essentially the same. Nutritionally, these products have in common a highly digestible protein with ample amounts of lysine and a relatively good essential amino acid pattern. Soybeans have contributed to food systems as sources of calories, as supplementary protein, and as complementary protein because of their good essential amino acid pattern. Furthermore, soybean protein products have made significant contributions to food systems because of their functional properties, which are essential to derive benefit from the nutritional or economic enhancement they impart to other foods. Many examples of this are found in the literature and in practice. Whole soybeans have been used to extend common beans, providing higher energy concentration and higher protein content and quality. Full-fat flour or protein concentrates added in variable amounts to cereal grain flours have introduced higher energy and higher protein content and quality into foods based on maize, rice or wheat. Finally, the amino acid pattern of soybean protein products has allowed them to be used as extenders for cow’s milk and meat products, without altering the protein quality or acceptability of the food product.     

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.     

Requirements for foods containing soy protein in the food for peace program

Under the Food for Peace Program, whole grains, milled wheat flour, milled rice, soybean oil, soybean flour, nonfat dry milk, soyacontaining blended food supplements, and soya-fortified processed foods are provided by the U.S. to needy people abroad to alleviate malnutrition. These commodities are used in maternal/child health programs, school feeding, food for work projects and disaster relief. The wide diversity of nutritional requirements and traditional food preferences has led to development of nine soya-containing food types, which are used in the PL-480 Title II donation program as blended food supplements or fortified processed foods. Research studies have led to the development of product specifications. Blended food supplements include the standardized mixtures of corn-soya-milk (CSM), instant CSM, wheat-soy blend and whey-soy drink mix. These foods, developed to fulfill the nutritional requirements of preschool children, contain from 17.5 to 29.7% either toasted-defatted or equivalent full-fat soya flour, along with vitamins and minerals. In addition, 4–19% soya oil is added to improve caloric density. These products contain 19 or 20% minimum protein and 6 or 19% minimum fat content. Fortified processed foods include soya-fortified bulgur (SFB), soya-fortified bread wheat flour (SFWF), soya-fortified cornmeal (SFCM), soya-fortified sorghum grits (SFSG), and soya-fortified rolled oats (SFRO). These foods contain toasted soya flour, grits, or flakes added at 12–15% levels. Fortified foods are generally consumed by people other than infants.     

Germination of soybeans and its modifying effects on the quality of full-fat soy flour

Usually, full-fat soy flour has some disadvantages in flavor, odor and stability. A soybean germination process was developed to improve the quality of full-fat soy flour. Advantages of the process were evaluated determining protein dispersibility index (PDI), trypsin inhibitor (TI) and lipoxygenase activities, milling capacity, odor and flavor score during the different stages of the process. In the final stages of the process, a marked decrease in lipoxygenase and TI activities were observed. The PDI increased with germination time in unheated soybeans. Odor and flavor scores improved substantially. Milling capacity dropped as germination time was increased.     

Government role and participation in development and marketing of soy protein foods

Japan has a history of utilizing soybeans as human foods. Currently, a great quantity of defatted soybeans is used as animal feed in Japan, and governmental and commercial enterprises are anxious to turn the defatted soybeans directly into foods for humans. Therefore, they are putting great efforts into soybean research and development. Since the demands for better foods are rising and their resources are not abundant, I feel that soybean protein will play an important role by exerting its unique properties, not only to supplement other foods, but also to grow into new types of foods when their unknown properties are disclosed.     

Soybean protein food in China

This paper introduces the history of soybeans and soybean protein foods in China. For 4,000 years, soybeans have been one of the main crops cultivated in this country. The history of extracting protein to prepare a protein food (bean curd, tu-fu) is about 1,000 years old. Our ancestors had long been aware of the edible value of the soybean and had developed a technique for preparing many kinds of soybean foods. The traditional methods of preparing soybean protein foods such as bean curd (tu-fu), fermented bean curd (fu-ru) and dried bean milk cream (fu-tsu) are discussed.     

Peanut protein: A versatile food ingredient

Peanut flour has been evaluated for use in a variety of food products as a replacement for animal source proteins. In breakfast cereals and snack foods, peanut flour blends well with cereal flours to yield products with excellent flavor, texture, and color. Peanut flour can be used to produce textured vegetable protein or can be used directly in ground meats to provide good moisture and fat binding characteristics. In bakery products, peanut flour can be used at levels up to 20% to provide protein supplementation without the astringent flavor of other oilseed flours.     

Flaking and extrusion as mechanical treatments for enzyme-assisted aqueous extraction of oil from soybeans

Flaking and extruding dehulled soybeans were evaluated as a means of enhancing oil extraction efficiency during enzyme-assisted aqueous processing of soybeans. Cellulase, protease, and their combination were evaluated for effectiveness in achieving high oil extraction recovery from extruded flakes. Aqueous extraction of extruded full-fat soy flakes gave 68% recovery of the total available oil without using enzymes. A 0.5% wt/wt protease treatment after flaking and extruding dehulled soybeans increased oil extraction recovery to 88% of the total available oil. Flaking and extruding enhanced protease hydrolysis of proteins freeing more oil. Treating extruded flakes with cellulase, however, did not enhance oil extraction either alone or in combination with protease. Discrepancies in oil extraction recoveries were encountered when merely considering crude free fat because some oil became bound to denatured protein during extrusion and/or sample drying. Bound fat was unavailable for determination by using the hexane extraction method, but was accounted for by using the acid hydrolysis method for total oil determination. Oil extraction recovery from extruded soybean flakes was affected by oil determination methods, which was not the case for unextruded full-fat soy flour.     

Physiologically Active Molecules and Functional Properties of Soybeans in Human Health—A Current Perspective

In addition to providing nutrients, food can help prevent and treat certain diseases. In particular, research on soy products has increased dramatically following their emergence as functional foods capable of improving blood circulation and intestinal regulation. In addition to their nutritional value, soybeans contain specific phytochemical substances that promote health and are a source of dietary fiber, phospholipids, isoflavones (e.g., genistein and daidzein), phenolic acids, saponins, and phytic acid, while serving as a trypsin inhibitor. These individual substances have demonstrated effectiveness in preventing chronic diseases, such as arteriosclerosis, cardiac diseases, diabetes, and senile dementia, as well as in treating cancer and suppressing osteoporosis. Furthermore, soybean can affect fibrinolytic activity, control blood pressure, and improve lipid metabolism, while eliciting antimutagenic, anticarcinogenic, and antibacterial effects. In this review, rather than to improve on the established studies on the reported nutritional qualities of soybeans, we intend to examine the physiological activities of soybeans that have recently been studied and confirm their potential as a high-functional, well-being food.     

Soy protein in feeding the elderly

Protein needs of the elderly may be moderately higher than those of younger adults when expressed as a percentage of total calories. Most experts recommend an intake of ca. 0.8 g protein/kg/day or ca. 12–15% of the total calories. Soya protein appears to be as good as animal protein in meeting the amino acid and protein needs of adult humans when consumed in adequate quantities. Attention must be given to the appropriate heat treatment and processing of soybeans to inactivate non-nutritional factors. The mineral and vitamin content of the diet should be monitored, because some of these nutrients may be altered or removed in the preparation of soya protein fractions or isolates for use in food products. Further research is needed to fully identify the nutritional requirements of the elderly, especially as affected by disease, trauma and drugs. In addition, nutrient interaction and bioavailability should be studied in foods which are processed by new techniques.     

Uses of defatted and partially defatted peanut flours

Defatted peanut flour produced by direct solvent extraction and partially defatted peanut flours produced by mechanical pressing have many potential uses in foods. The defatted peanut flour has a high protein solubility and is light colored, practically tasteless, and odor free. The defatted peanut flour has been evaluated as: an additive to increase the protein content of foods such as bread and other baked goods, macaroni, pancakes, and puddings; an extender in meats such as meat loaf and frankfurters; and an aid in preparing skim and full-fat (fat added) milk-like drinks and ice creams. The characteristics of this flour also make it useful in the preparation of protein concentrates (by air classification) and protein isolates. The partially defatted flour, with about 55% oil removed, is ideal for preparing full-fat, milk like drinks and can also be used in baked goods, ice cream, meats, and so forth. This flour can also be toasted to different degrees for use in foods such as baked goods, in which a nutty flavor may be desired. The “over roasted” flour has potential for use as a cocoa diluent.     

An overview of the phenolics of canola and rapeseed: Chemical,sensory and nutritional significance

Utilization of rapeseed meal in human foods has been thwarted by the presence of antinutritional factors such as glucosinolates, phenolics, phytates and hulls. The content of phenolics in rapeseed flour is nearly 30 times higher than that of soybean. Phenolic compounds contribute to the dark color, bitter taste and astringency of rapeseed meals. They may also interact with amino acids, enzymes and other food components, thus influencing the nutritional value of rapeseed meal and its products. Therefore, phenolic compounds are important factors when considering rapeseed meal as a protein source in food formulations. Available literature data on phenolic compounds and tannins of rapeseed/canola are fragmentary and diverse. Furthermore, developing a standardized method for analysis and quantitation of these compounds is warranted. Interaction of rapeseed phenolics/tannins with proteins and their effects on enzymes and other food components remain to be studied.     

Soy protein foods in U.S. assistance programs

Soy protein food products occupy an important place in both U.S. overseas and domestic food assistance programs. In the overseas food donation program the products serve as the source of protein for the fortification of conventional processed commodities—wheat flour, corn meal, rolled oats, bulgur, and sorghum grits—and as a major source of protein in several cereal soy products designed for special use as child food supplements. Acceptance of these products has been good and more than 1 billion lb. of soy-fortified foods were distributed in the overseas program during July 1, 1972-June 30, 1973. In domestic food assistance programs, soy protein foods which meet U.S. Department of Agriculture requirements have been introduced into both school lunch and breakfast programs and also are distributed to needy families. Two products, textured soy protein and protein-fortified enriched macaroni, are permitted to meet part of the meat requirement in the Type A school lunch. In the school breakfast program, soy protein is a permitted ingredient in protein-fortified foods such as doughnuts, cake-like baked products, and cereal-fruit products. They were introduced primarily to meet the need for nutritious food items that require no kitchen facilities to prepare and are convenient to serve in schools that lack food service facilities. Specifications for the various food products are presented.     

Soybean proteins in prudent-diet foods

A review is presented on soybean proteins and their health, nutritional, convenience, stability, and economic attributes that justify usage in prudent-diet foods. The concept of these foods is discussed with consideration the contributions of soybean proteins to caloric energy, ratios of polyunsaturated to saturated fatty acid, ratios of polyunsaturated to saturated fatty acids, cholesterol, sodium ion, and levels of sugars. Soybean proteins provide technologists with a cheap, functional protein source for developing meat analogs. Inherent soybean flavors are considered the major unstabilizing problem in prudendiet foods. The energy requirement for producing one pound of meat analog is estimated at 12,300 BTU; soy flour used in it requires only 330 BTU, while cooked meat requires approximately 52,250 BTU per pound.     

Soy proteins in foods—Retrospect and prospect

The soybean has been used for food in the Orient for centuries, but the western world has been slow to adopt it. In the last 40 years soybeans have become an important source of protein in poultry and livestock feed. In the last 10 years or so it has been used in foods in increasing amounts to supply low cost high quality protein with important functional properties. The soybean will be vital to meeting the protein needs of the future in all parts of the world, especially in the developing countries. The challenge is great to the plant breeders and agronomists to improve yields and adaptability of the crop and to the soy technologists to improve the characteristics of processed soybean proteins.     

Chemical constituents and protein food processing of rapeseed

In rapeseed, as in other oilseeds, there are some substances that adversely affect nutritional value. By application of appropriate technological processes, the antinutritive factors are removed and the final protein products appear to have high nutritive value. Compared with the soybean, rapeseed presents some unique problems. When processing rapeseed into protein foods, it is necessary to take into account high losses of nitrogen substances (nonprotein nitrogen), and higher costs of removing glucosinolates and their derivates, as well as phenolic compounds. Technically and economically feasible methods of reducing cellulose and phytate contents should be developed. In view of the presence of many constituents which lower the nutritional value of rapeseed protein products, it would appear that rapeseed is presently not a suitable raw material for production of food grade protein flour and grits. On the contrary, rapeseed protein concentrates and their texturates have satisfactory nutritional quality and feature good functional properties. Rapeseed isolates, except for poorer spinning properties, have similar characteristics to those of soybean isolates, but, as a result of low protein yields, their production is uneconomical. Recent progress in the breeding of glucosinolate-free and low fiber rapeseed varieties offers a new approach for development of processing methods for useful protein products based on this raw material.     

Evidence of an Enzymatic Source of Off Flavors in “Lipoxygenase-Null” Soybeans

The utilization of soybean products as food ingredients and foods is often limited by their beany-grassy flavor. Eliminating seed lipoxygenase (LOX) isozymes 1, 2 and 3 reduces the amounts of volatile off-flavor compounds in stored soybeans and soy products significantly, but they are not completely eliminated. The present work presents evidence that lipoxygenase-null (LOX-null) soybeans contain a LOX-like enzyme that is responsible for the off-flavors in LOX-null soybeans. Volatiles production in triple LOX-null soybeans was terminated by heat treatment, which suggests an enzymatic cause to the off-flavors. The source is LOX-like in that the volatile compounds produced are similar to LOX-generated products of polyunsaturated fatty acids. Oxygen was consumed when a LOX-null protein solution was incubated with crude soybean oil suggesting that the enzyme catalyzed oxygen consuming reactions. The generation of flavor compounds was inhibited by the typical LOX inhibitors propyl gallate and nordihydroguaiaretic acid (NDGA). The enzyme appears to be more active with phosphatidylcholine than with other lipid substrates. The cause of the off-flavors in LOX-null beans appears to have enzyme-like characteristics. This is the first report of the initial characterization of this LOX-like enzyme.     

Soy and corn flour precooked with microwaves and its use in the preparation of arepas]

Unhusked corn and soy grits were used as raw material, with a particle size ranging between 10 and 20 mesh (ASTM). The results obtained in this study reveal that microwave heating is effective in destroying the antinutritional factors present in soybeans. The trypsin inhibitor activity, in effect, was reduced to a 76% inactivation. The hemagglutinating titer was labile to the heating process, showing values of +8 to +3 for the full-fat soy flour and precooked soy flour, respectively. The quality of soy protein was measured by the protein efficiency ratio (PER) showing values of 2.63 for the precooked soy flour, and 2.46 to 2.21 for the precooked corn:soy blends (70:30 and 50:50). These uncooked blends present values of 1.17 and 1.04. The enriched corn:soy flour had a PER value of 1.60, in comparison to casein (PER = 2.90). The microwave heating improved the digestibility of the soy flour and blends. There were no significant differences (P less than or equal to 0.05) in relation to the functionality of the precooked flour and mixtures. The results obtained revealed that the applied process markedly improve the functional properties and nutritional value of the enriched flour, and of the "arepas" prepared from them.     

Food uses of peanut protein

Approximately 19 million metric tons of peanuts (Arachis lypogae L.) are harvested annually, and contribute over 3.5 million tons to the world’s protein pool for food and feed uses. Peanut is the world’s fourth most important source of edible vegetable oil and the third most important source of vegetable protein feed meal. About 70% of the U.S. Crop is consumed domestically or exported as peanut kernels, peanut butter, and confections. Crushing is limited primarily to culls and kernels containing aflatoxin; and to stabilize the market. However, in countries such as India, Senegal, Brazil and Argentina, 75 to nearly 100% of the crop is crushed or exported for use as oil and livestock meal. The peanut is perhaps the world’s most widely researched food protein oilseed. Advantages over other oilseeds include relatively bland flavor, minor color problems, and minimal preparation requirements. Products in use throughout the world include boiled peanuts, roasted full-fat or partially defatted peanuts, peanut butters, grits and flours (full-fat or defatted), defatted peanuts, protein concentrates, and protein isolates. Compounded food applications include fortified breads and bakery products, snacks, meat products, extended milks, cheese and curd type products, and various mass-feeding foods in developing countries. Challenges encountered in peanut utilization include improvement of flavor levels and stability, identification of nutritional adequacy and fortification requirements, elimination of antinutritional factors, development of new products and improved processes, and elimination of aflatoxin problems.     

Separating Oil from Aqueous Extraction Fractions of Soybean

Previous research has shown that enzyme-assisted aqueous extraction processing (EAEP) extracts 88–90% of the total soybean oil from extruded full-fat soy flakes into the aqueous media, which is distributed as cream (oil-in-water emulsion), skim, and free oil. In the present work, a simple separatory funnel procedure was effective in separating aqueous skim, cream and free oil fractions allowing mass balances and extraction and recovery efficiencies to be determined. The procedure was used to separate and compare liquid fractions extracted from full-fat soy flour and extruded full-fat soy flakes. EAEP extracted more oil from the extruded full-fat soy flakes, and yielded more free oil from the resulting cream compared to unextruded full-fat soy flour. Dry matter partitioning between fractions was similar for the two procedures. Mean oil droplet sizes in the cream and skim fractions were larger for EAEP of extruded flakes compared to non-enzymatic AEP of unextruded flour (45 vs. 20 μm for cream; 13 vs. 5 μm for skim) making the emulsions from EAEP of extruded flakes less stable. All major soy protein subunits were present in the cream fractions, as well as other fractions, from both processes. The cream could be broken using phospholipase treatments and 70–80% of total oil in the extruded full-fat flakes was recovered using EAEP and a phospholipase de-emulsification procedure.