Direct consumption of the soybean

Efforts in some Latin American countries directed toward the use of soybeans as a primary source of proteins for human nutrition have especially focused attention on simple home-level procedures such as the soaking and cooking of soybeans and the lime-cooking of corn-soybean mixtures. Data obtained with these two procedures indicate there is great potential in using soybeans directly in human feeding. Soaking soybeans in 0.25% NaHCO₃ for 8 hr and cooking for 20 min decreases trypsin inhibitor activity more than 80%, and 40 min of cooking gives chewiness indexes similar to those of common beans with acceptable texture (10–20). The protein efficiency ratio (PER) of a mixture that was 50% soybeans and 50% common beans was 60% higher than that of common beans alone. Considering acceptability and functional characteristics of “masa” (dough) and “tortilla,” an optimum soybean level within the lime-cooking procedure was found to be 16%. Green pods of soybean varieties adapted to the tropics, at 65 to 85 days of maturation, have the same nutrient content (dry basis) as mature soybeans, with a good quality protein and a good content of B complex vitamins.     

Microwave roasting and phospholipids in soybeans (Glycine max. L.) at different moisture contents

The effects of microwave roasting on phospholipids in soybeans were investigated in relation to moisture. Whole soybeans at different moistures (9.6, 38.2, and 51.9%) were roasted by exposure to microwaves at a frequency of 2,450 MHz. During microwave treatments, the lower the moisture content, the higher was the internal temperature in soybeans at the end of microwave roasting. Total lipids were extracted from the beans after microwave treatment, and the phospholipids were separated with thin-layer chromatography. Phosphatidylcholine was the principal phospholipid in the extracted lipids from all unroasted and roasted bean samples. After microwave roasting, phospholipids containing an amino group, especially phosphatidylethanolamine, decreased substantially (P<0.05) in lower-moisture soybeans. However, increasing the moisture content depressed a rise in the internal temperature of soybeans and prevented a reduction in phospholipids and/or polyunsaturated fatty acids in the phospholipids. Based on the changes in the composition and fatty acid distribution of phospholipids in soybeans during microwave roasting, it is necessary to consider the moisture content in soybeans when roasting in a microwave oven.     

Water absorption of soybeans

The rate of water absorption of U.S. and Japanese soybeans has been measured at 10° and 25°C. and at initial moisture levels ranging from 7.5 to 14.0%. The principal controlling factor in absorption of water is the seed coat. However the rate of water absorption of sound whole beans is also influenced by the initial moisture level in the beans; the lower the moisture the slower the rate of water absortion. The presence of hard beans also reduces the rate of water absorption. U.S. soybeans usually have lower moisture and contain more hard ones than do Japanese beans. These factors are attributed to the climatic differences of the two countries. No fundamental differences were found in the rate of water absorption of U.S. and Japanese soybeans. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Cooking procedures for direct consumption of whole soybeans

The purpose of this research was to determine adequate conditions for the preparation of soybeans at home level. In accordance with the results, soaking the soybeans for eight hours in a 0.25% bicarbonate solution, gives the appropriate hydration to the soybeans, which can then be easily cooked. Boiling them at atmospheric pressure during 20 minutes was required to destroy 80% of the soybeans antitrypsin activity, and a high PER was also obtained. Nevertheless, the soybeans texture was not satisfactory; therefore, longer boiling periods were tested so as to establish the most suitable time needed to achieve a softness similar to that of common beans as usually consumed. Softness was measured instrumentally, and the optimal conditions found were: 40 min boiling after 8 hr soaking in a 0.25% bicarbonate solution. Under these conditions, the PER and NPU values increased 18% and 33%, respectively, with respect to those of the casein PER and NPU. It is concluded that with this procedure, large amounts of protein can become available at an equivalent price to US$0.40/kg ($80.00/kg).     

Oil quality from hydraulic pressed soybeans

Summary HYDRAULIC pressed soybean oil quality is affected a great deal by the moisture of the beans at the time of milling. At moistures above 12 to 13% the oil quality deteriorates sharply. A great improvement in the oil from wet or even moisture damaged soybeans can be made by drying the beans in below 12% before milling. Even badly deteriorated (sample grade) beans have been vastly improved. Blending of wet and dry soybeans to an average moisture below 12% does not seem to yield as good quality oil as drying wet beans to a corresponding moisture. Normal variations in other soybean characteristics determining bean grade have lesser effects on soybean oil quality. Some data on the effect of bean damage, splits, off-color varieties, and foreign material are included in this paper. Hydraulic oil mills operating on soybeans will be able to make large improvements in oil quality by drying whole wet beans at the mill and by removing foreign material from the beans.     

Cracking and dehulling shriveled and wrinkled soybeans

Midwest drought conditions in 1988 resulted in soybeans with shriveled and wrinkled seed coats. Processors expressed concerns about the processing of such misshapen seeds. The objective of this research was to determine the cracking and dehulling properties of shriveled and wrinkled (S/W) soybeans. Five lots of soybeans, two sound lots and three containing shriveled and wrinkled seeds, were cracked and dehulled, as were the sized and sorted fractions of these lots. Processing variables (% aspiration liftings, fiber removal in the liftings, % fines in the liftings, protein recovery, oil recovery, meats size distribution and oil-free meats fiber content) indicated significant differences between whole sound lots and whole lots containing S/W. There were differences in processing properties between these three types of soybeans (from best to worst)-sound soybeans from sound lots, sound soybeans from lots containing S/W beans and S/W soybeans. Size had an effect on processing; smaller beans did not process as well. The economic impact of S/W conditions was estimated by using a simulation model of soybean processing. Although the presence of S/W soybeans affected cracking and dehulling properties, it had a negligible effect on the Estimated Processed Value per Bushel (EPVB). Calculated blends of sound and S/W lots containing 20% S/W seeds had a decrease in EPVB of less than 0.2%.     

Water imbibition by normal and hard soybeans

By observing the imbibition of dyed water, soybeans were classified into damaged (break in seed coat), normal and hard beans. Hard soybeans were unique in having a long, variable lag time before start-ing imbibition, but once water uptake was started, the rate was similar to that of normal beans. Soaking hard beans in methanol or ethanol for 24 hr at 20 C made them permeable to water. The cuticle was the most likely site of the water barrier in the seed coat of soybeans. Journal Paper No. J-10206 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project No. 2159.     

Specificity of lipase from several seeds andLeptospira pomona

The specificities of lipase preparation from oats,Leptospira pomona DM₂H, corn, soybeans, safflower seed and pinion nuts were examined by using cocoa butter, lard and corn oil as substrates. Oat lipase exhibited an acyl group specificity, favoring the hydrolysis of linoleyl groups and discriminating against stearoyl groups. TheL. pomona lipase exhibited a tendency to hydrolyze acyl groups on the 1 and 3 positions of glycerol preferentially. The hydrolysis by the other seed lipases was nonspecific. Journal Paper No. J-6316 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project 1517.     

Significance for humans of biologically active factors in soybeans and other food legumes

Among the many biologically active factors present in the soybean, only protease inhibitors (PI) have been shown to exert significant adverse effects on animals consuming diets containing soybean protein. Evidence is presented to suggest that (a) PI are only partially responsible for the poor nutritive value of inadequately processed soybeans, (b) low levels of PI are relatively harmless to animals, (c) human trypsin is only weakly inhibited by PI, and (d) the human pancreas is probably insensitive to the hypertrophic effects of PI. Parelleling the wide spread distribution of PI in the plant kingdom are the so called phytohemagglutinins or lectins. Unlike the lectin present in soybeans which appears to have only a marginal effect on the nutritional quality of the protein, the lectin of the common bean (Phaseolus vulgaris) is quite toxic. Moreover, the major storage protein of such beans is quite resistant to digestion unless denatured by heat, thus emphasizing the importance of adequate processing of those legumes when used in the human diet. Although goiter-inducing compounds are present in most cruciferous plants and cyanide-producing substances may be found in cassava and lima beans, traditional methods of preparation and present technology have served to minimize any harmful effects that may accompany the ingestion of these foods by man. Brief mention will also be made of two human diseases, lathyrism and favism, associated with the consumption ofLathyrus sativus andVicia faba, respectively, their causative agents and mechanism of action. Although there are numerous examples of so called toxic constituents in legumes, they nevertheless have provided a valuable source of protein to man over the centuries. This can be attributed, in part, to the fact that man has learned how to detoxify them by suitable preparative measures. The varied nature of our diet also minimizes the contribution of a toxicant from any one foodstuff. Nevertheless, there is the ever present possibility that the prolonged consumption of a particular legume that may be improperly processed could bring to the surface toxic effects that otherwise would not be apparent. As the shortage of protein becomes more acute, it is not unlikely that much of the population of the world will be faced, in the future, with a more limited selection of protein-foods, most of which will be of plant origin and, hence, potential carriers of toxic constituents. The food scientist should at least be cognizant of such a possibility and be prepared to apply his knowledge and skill to meeting this challenge.     

Factors promoting the formation of nonhydratable soybean phosphatides

Whole, cracked and flaked soybeans were stored under a variety of conditions. After extraction with hexane, the crude oils were degummed in the laboratory, and the nonhydratable phospholipid (NHP) content was estimated from the phosphorus content of the degummed oil. Results showed that four interrelated factors promote NHP formation. These include (i) moisture content of beans or flakes entering the extraction process; (ii) phospholipase D activity; (iii) heat applied to beans or flakes prior to, and during, extraction; (iv) disruption of the cellular structure by cracking and/or flaking. Results from this study suggest that NHP formation can be minimized by control of the moisture of beans and/or flakes entering the extraction process, inactivation of phospholipase D enzyme, and optimizing temperatures during the conditioning of cracked beans or flakes. Presented at the 82nd Annual Meeting of the American Oil Chemists’ Society, Chicago, IL, May 12–16, 1991.     

Effect of soybean pretreatment on the color quality of soybean oil

Color reversion in soybean oil can be prevented by reducting the enzyme activity of soybeans before cracking and flaking. Soybean oil extracted from steamed, intact soybeans (18% moisture) had lower Rm (max. red) values in RBD oil, higher amounts of γ-tocopherol, plus its isomers, in both crude and RBD oil, and also higher amounts of hydratable phosphatides in crude oil than those in the oils from the same beans without steam treatment. For soybean pretreatments, a toasting process is less effective than the steaming process for the inhibition of color reversion of soybean oil. To prevent the occurrence of color reversion in RBD soybean oil, the amount of γ-tocopherol and γ-TED (5-[tocopheryloxy]-γ-tocopherol) should be above 550 ppm in crude oil.     

Rhamnolipid Effects on Water Imbibition,Germination, and Initial Root and Shoot Growth of Soybeans

Rhamnolipid is a nontoxic and biodegradable bioproduct that offers sustainable solutions in agricultural, pharmaceutical, cosmetic, and refinery applications. Its imminent uses in agriculture warrant thorough investigations of rhamnolipid interactions with plants. In this work, the effects of rhamnolipid on soybeans during imbibition and germination under different conditions were studied. Seed coat was determined to serve as the main barrier that regulates water imbibition, and rhamnolipid at 2 g L⁻¹ was found to increase the imbibition rate to 16.1 (% dry bean weight)/h from 12.6% h⁻¹ at 0 g L⁻¹ rhamnolipid in intact soybeans for 0.5–5 h, when the soybean weight increased almost linearly due to the constant permeation rate through hydrated seed coat. Rhamnolipid, however, did not transport freely into beans; only about 50% of the rhamnolipid carried in the volume of water imbibed was absorbed by beans. Two different studies showed that absorbed rhamnolipid, from up to 1.5 g L⁻¹ solutions, did not affect the germination percentages in wet cloths and soil pots. However, an additional study with constant (7-day) exposure of germinating beans to more concentrated rhamnolipid solutions indicated a slight decrease of germination percentage, down to ~85% at 20 g L⁻¹ rhamnolipid. Rhamnolipid had far more pronounced effects on root development. At high concentrations (5–20 g L⁻¹), rhamnolipid severely stunted the root growth, causing reduced root and shoot weights and visible browning and damages of roots; however, low (0.5–1 g L⁻¹) concentrations of rhamnolipid stimulated higher lateral root development while reducing the primary root extension, causing no change in the overall root or shoot weight. The findings indicated complex rhamnolipid interactions with soybeans and warranted further study while developing agricultural applications of rhamnolipid.     

Postharvest handling of soybeans: Effects on oil quality

Effects of postharvest handling (such as storage and transportation) of soybeans on the quality of extracted oil were evaluated. Identity-preserved export shipments of soybeans were sampled at origin points and at destination ports. Samples of new crop beans were also acquired from domestic elevators. Lots were separated to yield three fractions each: original, whole beans, and split beans. Crude oil extracted from each fraction was characterized for free fatty acid content, iron content, peroxide value, phosphatide, nonhydratable phosphatide, color, Chromatographic refining loss, and fatty acid composition. Oil extracted from split beans had free fatty acid and iron contents significantly greater than those of oil from whole beans. These two deleterious qualities of crude oils were found to increase during shipment. Degumming studies showed an increase in the nonhydratable phosphatide content of extracted oil due to shipment. Presented at AOCS Meeting, St. Louis, MO, May, 1978     

Production and functional characteristics of protein concentrates

Protein concentrates derived from common dry beans (Phaseolus vulgaris L.) may improve world protein resources, reduce on-site preparation time and expense and provide improved nutrition. Several different methods have been studied for the production of these concentrates, including alkali extraction and isoelectric precipitation, ultrafiltration, air-classification and salt extraction under high salt concentrations. Recent studies using solid-solid dry roasting, pin milling and air-classification resulted in the following percent mass fractions: hull/fiber (10%), coarse/starch (70%) and fine/protein (20%). Results indicated that the protein fractions were approximately 45–50% protein, low in raffinose and stachyose and hadtrypsin inhibitor activity reduced to about half of that of raw beans. Nitrogen Solubility Index (NSI) ranged from 33–70% and was associated with the thermal conditions applied during dry roasting. The flours had a bland flavor without the bitter off-flavors which have traditionally limited the use of dry beans in formulated foods. Most minerals and phytic acid tended to be associated with protein flour; however, although iron may have been bound to phytic acid, its absorption by anemic rats was not hindered by the presence of endogenous phytic acid. These flours produced acceptable products when incorporated into cookies, doughnust, quick breads and leavened doughs. Presented at the 78th American Oil Chemists' Society Annual Meeting, May 27–21, 1987, New Orleans, LA.     

A new approach to genetic alteration of soybean protein composition and quality

Although soybeans produce high-quality meal, modern animal and fish production systems often require synthetic essential amino acid supplements to fortify feed rations. However, biotechnology may enable development of soybeans with naturally adequate levels of certain essential amino acids for advanced feed formulations. One approach involves genetic manipulation of glycinin (11S) and β-conglycinin (7S) contents, the principal components of soybean storage proteins. Because 11S contains more cysteine and methionine than 7S protein, a higher 11S:7S ratio could lead to beneficial changes in the nutritional quality of soybean meal. Although genotypic variation for 11S:7S may be low among soybean [Glycine max (L.) Merr.] germplasm, ratios ranging from 1.7–4.9 were observed among accessions of the wild ancestor of cultivated soybean (Glycine soja Sieb, and Zucc.). Thus, wild soybean germplasm was evaluated as a potential source of genes that govern protein synthesis that may have been lost during the domestication of G. max. Change in the amount of 11S protein accounts for a significant portion of the genotypic variation in protein concentration and composition among wild soybeans. Strong positive correlation exists between the 11S:7S ratio and methionine or cysteine concentration of total protein. Moderate positive associations were found for threonine or tyrosine. A moderate negative correlation was found between lysine and 11S:7S. No association was found for leucine and phenylalanine or for total essential amino acid concentration. Based on these data, G. soja may contain a different complement of genes that influence expression of 11S and 7S proteins than G. max germplasm. Thus, through interspecific hybridization, wild soybeans may be a useful genetic resource for the further improvement of protein quality in cultivated soybeans.     

Factors affecting the content of tocopherol in soybean oil

The state of soybeans prior to extraction affected the tocopherol content of crude soybean oils. Soybean flakes with a thickness of 0.16–0.33 mm had higher extracted oil yield but a slightly lower tocopherol content of the oils than did cracked beans and thicker bean flakes. Highmoisture content and long storage of soybeans resulted in lower tocopherol content in the crude oils, with moisture content being more important than storage time at decreasing the tocopherol content of oils. Soybean oil from stored beans with 15±1% moisture content led to a more significant decrease in the tocopherol content than did oil from stored beans with low (12%) or high (18%) moisture contents. Soybean flakes contaminated with oxidized oil had a significant effect on the decrease of the tocopherol content in crude oils. The high amount of phospholipids in crude soybean oil might result in a smaller decrease in the tocopherol content of oil during heating.     

Effect of moisture,microwave heating,and live steam treatment on phospholipase D activity in soybeans and soy flakes

The impact of enzyme activity on the nonhydratable phospholipid content of crude soybean oil has been evaluated. A radiochemical method was used to assay phospholipase D activity in whole and flaked soybeans stored under a variety of storage and enzyme inactivating conditions. The crude enzyme was isolated and incubated with a mixture of¹⁴C-labeled and unlabeled phosphatidylcholine. The amount of liberated radioactive choline was used as a measure of enzyme activity. whole soybeans with moisture contents of 8–18% were stored at 40°C and sampled weekly for up to four weeks. Although the enzyme was active in all samples, the optimum moisture content for enzyme activity was about 14%. Flaking and flake thickness were shown to increase phospholipas D activity. At moisture levels above 10%, flakes at .012″ showed about twice the activity of whole beans. As flake thickness was increased, enzyme activity decreased. Whole soybeans with moisture contents of 12–18% were treated by microwave heating under controlled conditions. During the early stages of heating, the enzyme was activated, and then was gradually destroyed by the time the temperature of the beans reached 115–120°C. Approximately 8–10 min of microwave heating was required to completely destroy enzymatic activity. The inactivation of phospholipase D in soyflakes treated with live steam was also evaluated. The enzyme is rapidly destroyed at temperatures of about 110°C. Evaluations of flakes subjected to live steam and whole beans treated by microwave heating to inactivate phospholipase D suggest that heat, moisture and enzyme activity are important factors contributing to the formation of nonhydratable phospholipid in extracted crude oils. Presented at Annual Meeting of the American Oil Chemists' Society, May 3–7, 1989.     

Tofu and tempeh as potential protein sources in the western diet

In recent years, a growing interest in foods of plant origin, especially plant protein foods, has become evident. A large number of low-technology, Oriental soybean foods have appeared on the American market outside the Oriental community. The most popular one is tofu. Tempeh, another soybean protein food, also has attracted a lot of attention. Tempeh has not yet been accepted to the extent that tofu has, but it is becoming a hamburger-alternative for vegetarians, now numbering 10–15 million in the United States. According to information published by the Soyfoods Center of California, the number of tofu producers in North America rose from 50 in 1975 to 182 in 1983, and annual production has increased from 13,250 tons in 1979 to 27,500 tons in 1983. The annual tempeh production was estimated at 500 tons in 1982. Changes in the perceptions of soybean foods as they pertain to health and social status seem to be the determining factors behind the momentous expansion of Oriental soybean foods. Therefore, the growth trend is expected to be continuing for some time into the future. Tofu is made by curdling the protein with a calcium or magnesium salt from a water extract of whole soybeans. It is a highly hydrated, gelatinous product with a soft, smooth texture and a bland taste. Therefore, tofu can be easily incorporated with other foodstuffs and used in nearly every culinary context, from salad to dessert and from breakfast foods to burgers. Tempeh is made by fermenting boiled soybeans withRhizopus oligosporus. After 20–24 hr at 30 C, the beans are covered with white mycelium that binds the beans together to form a firm cake. It can be seasoned, and cooked by frying, roasting or baking — just like meat. Presented at the symposium on Potential New Protein Sources 75th AOCS Meeting, Chicago, 1983.     

Flavor and oxidative stability of oil processed from null lipoxygenase-1 soybeans

The role played by lipoxygenase in the flavor quality of soybean oil was investigated by comparing the oil processed from special soybeans lacking lipoxygenase-1 (Forrest x P.I. 408251) with the oil from normal (Century) beans. Quality assessment was based on sensory evaluations and on capillary gas chromatographic (GC) analyses of volatiles of the extracted crude, partially processed, and refined, bleached and deodorized oils. In direct comparisons of oil products from the two types of beans, no significant differences were found in either flavor quality or in flavor stability based on total volatiles, and in analyses for 2,4-decadienal. Although thermal tempering did not significantly affect the initial flavor scores of crude and degummed oils from Century and low L-1 soybeans, the initial scores of refined and bleached oils from Century soybeans were significantly improved by this treatment. Similarly, thermal tempering was just as important in producing good quality flour from the special beans lacking lipoxygenase-1 as the flour from normal beans. Therefore, factors other than lipoxygenase-1 appear to affect the food quality of soybean oils and meals.