Chemical composition and evaluation of the protein quality of beans in adult humans by the short-term nitrogen balance method

Three varieties of common beans were chemically analyzed and their protein quality was evaluated in 12 human male adult subjects by the short-term nitrogen balance method. Chemical analyses were performed for both raw and cooked grains. Cooking reduced the trypsin inhibitors in 28 to 73%, hemagglutinins, 100%, tannins as acid tannic equivalents, 9 to 72%, and 55 to 75% as catequin equivalents, and alkali-soluble nitrogen in 65%. Red and black beans contained more residual trypsin inhibitors and tannins than white beans, while the latter contained more alkali-soluble nitrogen. Although cooked colored beans had more antinutritional factors that affect protein digestibility, their protein quality was similar to that of white beans. This could be explained by the fact that the amino acid composition and/or balance of red and black beans absorbed nitrogen is better than that of white beans, so that the final nutritional value will be determined by the sum of interactions between all factors. In this study, each of the three varieties presented at least one protein quality depressor in higher concentration than the other two varieties. Therefore, the overall differences found between treatments and residual effect, were small or non existent, while significant differences (p greater than 0.05) were found between subjects and nitrogen balance periods. A level of 0.65 g of bean protein/kg/day was not enough to maintain nitrogen balance in subjects fed a diet where beans were the only protein source. According to calculations, 0.9-1.0 g of bean protein/kg/day are necessary for nitrogen balance in male adults, and 1.2-1.3 g of protein bean would be the recommendation for a normal population.     

The protein quality of commercial products of texturized soybean protein and meat mixtures

The purpose of the present study was to evaluate the protein quality of eight commercial samples of texturized soybean protein (TSP) collected in the food markets of various Latin American countries. The study also included experiments designed to establish the limiting amino acids in those products, and studies to evaluate the process of texturization by extrusion cooking. Finally, experiments were also carried out to evaluate the effect of replacement of meat by TSP as well as the supplementary value of the latter to tortilla flour. The eight samples were characterized for their functional properties and protein quality. The results obtained indicate that all samples were different in density, water absorption, and nitrogen solubility. Likewise, all samples were different in their lysine, methionine and threonine content, with PER values ranging from 1.75 to 2.31. Protein quality standard value is 2.3. The amino acid supplementation studies showed a positive significant response to methionine addition, particularly in those products exhibiting low PER values. The addition of both lysine and threonine to the methionine-supplemented product, increased PER significantly. The data also demonstrated that replacement of more than 25% of meat protein by TSP protein decreased protein quality of the product, even when a TSP with an accepted protein quality value was used. This product was also found to supplement the quality of tortilla protein. Finally, it was established that the texturization process did not reduce the protein quality of soybean protein. Based on these results, it is concluded that the variability in the protein quality measured in the eight TSP samples was due to the initial quality of the soy flour texturized, which was already damaged before texturization. For this reason, it is recommended that Latin American countries establish TSP quality standards when this product is used as a protein extender for meat, and that appropriate systems be implemented for the quality control of such products.     

Germinated soybean protein products: Chemical and nutritional evaluation

Various protein fractions were prepared from non-germinated and germinated soybeans utilizing a combination of calcium chloride and sodium alginate solutions as extractant. Germination tended to improve the nutritional quality of the protein products as measured by protein efficiency ratios (PER of standard rat bioassay). PER values of proteins containing sodium alginate were reduced significantly, which was attributed to inhibition of pepsin proteolysis. Only 30 percent of the trypsin inhibitor activity in raw soybeans was eliminated during germination for three days. Vitamin C content increased from 0 to 25 mg per 100 g (dry basis) during germination.     

Rat models in protein quality evaluation

The ideal methodology for establishing protein quality has not yet been elaborated. On the other hand, the proposed introduction on the market of novel protein sources urges the industry to ask for an in vitro test, characterized for being inexpensive fast, reliable, and acceptable at an official level. Obviously, the in vitro test must be confirmed by an appropriate in vivo test. In this connection the problems relative to the species on which to experiment if it should or should not be the one to whom the protein food is directed—and the characteristics of the in vivo test are discyssed. Although the rational appears to be to assay on man protein directed to him, the cumbersomeness of the procedure, technical difficulties, uncertainties in the interpretation of the results as wel as ethical considerations for what children are concerned, don’t favor experimentation on man. An extensive experimental study, aimed at testing various conventional and novel proteins, confirmed that the multiple doses test, as proposed by Samonds and Hegsted (RPV), has the highest discriminating capacity and is scientificically the most reliable. A research project to verify the correlation between the two methods for evaluating biological quality, namely PRV and the method of the in vitro ultrafiltered digest (EUD), is under investigation.     

Effectiveness of methods for evaluating the nutritional quality of soybean protein

Various approaches can be used for the nutritional evaluation of protein sources. These include human and animal bioassays and microbiological, enzymic and chemical in vitro methods. Examples of the application of each of these approaches for the evaluation of soya protein sources are presented and evaluated in this paper. The ineffectiveness of rat assays for predicting nutritive value of soya protein for humans is documented. Current procedures, based on rat bioassays, which are used for nutritional labeling of dietary protein sources in the U.S. and Canada are discussed and alternative approaches described. In particular, the use of in vitro methods for estimating amino acid composition and essential amino acid bioavailability may have significant advantages for estimating the nutritive value of soya protein sources for human consumption.     

Flavor evaluation of crude oil to predict the quality of soybean oil

Reliable methods for evaluation of crude oils are needed to assist processing and to improve flavor quality of finished products. The quality of crude oils from soybeans of different sources and treatments was determined by sensory evaluation and by capillary gas chromatographic (GC) analyses of volatiles. Taste panelists were specially trained in using a new technique to evaluate crude oils by dilution and comparison with freshly deodorized oils. The flavor quality of crude oils from untempered soybeans was significantly poorer than that of oils from soybeans steam-tempered at 104 C for four min. Capillary GC analyses of total volatiles and hexanal correlated well with differences in flavor quality and stability. Crude oils extracted from soybeans damaged by storage at 45 C and 13% moisture received decreasing flavor scores with prolonged storage time. Similarlly, hexanal and total volatile contents increased with storage times. Commercial crude oils from several geographic locations showed a wide range in flavor scores. However, flavor scores of crude oils showed good agreement with flavor stabilities (decrease in flavor scores after storage at 60 C) of the corresponding oils after refining, bleaching, and deodorization. Therefore, the combined use, of sensory evaluations and GC-volatile analyses of crude oils can provide convenient, rapid, sensitive and reliable screening methods to assist in improving the quality of finished soybean oils by controlling soybean storage and processing.     

Regulatory aspects of mycotoxins in soybean and soybean products

More than 50 countries have enacted or proposed regulations for the control of aflatoxins in foods and/or feeds, and at least 15 of these countries also have regulations for permitted levels of contamination by other mycotoxins. Since 1965, the U.S. Food and Drug Administration has used action levels to control aflatoxins in its compliance programs. Cooperative programs with the U.S. Department of Agriculture, state agencies, and industry also have been used to keep exposure to aflatoxins as low as practical. Soybeans support the growth of many mold species, which can produce toxins such as aflatoxins, trichothecenes (such as T-2), and cytochalasins. The natural occurrence of these toxins in soybeans has not been a problem. Limited surveys of soybeans and soy-based infant formulas have not revealed significant contamination. The sequence of events that leads to consideration of a mycotoxin for control programs and other regulatory activity includes determination of a toxic response, isolation and identification of the toxin, development of a sampling plan and method of analysis, and determination of incidence and levels of contamination of the susceptible commodity. The quality of soybeans can vary widely, depending on environmental, agronomic, and storage conditions. products susceptible to contamination from improper storage are subject to regulatory action on a case-by-case basis. The government-industry cooperative programs have been successful in limiting human exposure to aflatoxins.     

Induced resistance in soybean toHelicoverpa zea: Role of plant protein quality

Resistance in soybean toHelicoverpa zea is comprised of both constitutive and inducible factors. In this study, we investigated the induction of resistance byH. zea in both greenhouse and field studies. In a greenhouse experiment, fourth-instarH. zea growth rates were reduced by 39% after 24 hr feeding and by 27% after 48 hr when larvae fed on previously wounded V3 foliage (cv. Forrest) compared with undamaged foliage. In a field study, the weight gain by larvae was more than 52% greater when larvae fed for 72 hr on undamaged R2/R3 soybean plants (cv. Braxton) compared to those that fed on previously wounded plants. A significant component of the induced resistance is due to a decline in the nutritional quality of foliar protein following foliar damage byH. zea. Foliar protein was extracted from damaged and undamaged foliage and incorporated into artificial diets. Larval growth was reduced 26% after four days and 49% after seven days on diets containing protein from damaged plants compared to larvae feeding on foliar protein from undamaged plants. Chemical analyses of protein quality also indicated a decline in quality in damaged plants compared to unwounded plants. Increases in lipoxygenase activity (53%), lipid peroxidation products (20%), and trypsin inhibitor content (34%) were observed in protein from wounded plants. Moreover, a 5.9% loss in free amines and 19% loss in total thiols occurred in protein from wounded plants. Larval feeding causes a significant increase in foliar lipoxygenase activity that varied among genotypes. Lipoxygenase isozymes were measured at pH 5.5, pH 7.0, and pH 8.5 in V3 stage plants of Forrest, Hark, D75-1069, and PI 417061 genotypes. Lipoxygenase activity in each genotype was significantly increased after 72 hr of larval feeding at each pH level tested, with the exception of lipoxygenase isozymes at pH 5.5 in genotype PI 417061. Larval feeding on R2/R3 stage plants (field-grown cv. Braxton) for six days also increased foliar lipoxygenase activity.     

Improving the quality of the soybean

Soybeans, once a relatively minor farm commodity, have become the world’s most abundant source of vegetable protein and oil. This growth in popularity, much of which has occurred in the last 20 years, has been made possible partly by genetic improvements that have successfully adapted soybeans to a wide variety of environmental conditions. To date, however, soybean breeders have concentrated their research efforts on increasing the quantity rather than the quality of soybeans. This paper summarizes genetic research currently underway to improve the quality of soybeans and/or soybean products. It also examines research efforts to improve the soybean’s fatty acid composition, change the amino acid profile and reduce antinutritional factors.     

Comparison of kjeldahl and dumas methods for determining protein contents of soybean products

The Kjeldahl and Dumas methods for quantifying nitrogen content were compared using nine soybean products having protein contents ranging from 0.5 to 90%. In addition to comparing day-to-day variability of the Dumas method, differences between and variabilities of two Kjeldahl systems and Kjeldahl operators were also evaluated. The Kjeldahl method gave slightly, but significantly, lower values than did the Dumas method. Both the Kjeldahl and Dumas methods had equivalent variabilities (same SD about the means). The ratios between the means for the Kjeldahl and Dumas (K/D) protein values ranged from 0.66 to 1.03. The conversion equation y=−0.00536+0.97188x (R ²=0.9997) was developed and validated to convert from Dumas to kjeldahl protein concentrations.     

Microencapsulation of capsanthin by soybean protein isolate‐chitosan coacervation and microcapsule stability evaluation

Although capsanthin possesses excellent coloring performance and healthcare functions, its application in the food industry is limited due to its susceptibility to humidity, heat, and light. The purpose of this research was to microencapsulate capsanthin by soybean protein isolate (SPI)‐chitosan coacervation and evaluate whether the microencapsulation improved the stability of capsanthin against the adverse conditions mentioned above. The results indicated that the optimum conditions for capsanthin microencapsulation were emulsification speed 10,000 rpm, emulsification temperature 45°C, wall concentration 15 g/L and core to wall ratio 1:2 (w/w). Under these conditions, the droplets in the emulsion were even in size distribution without agglomeration and the microencapsulation efficiency and microencapsulation yield reached 90.46% and 86.69%, respectively. Microencapsulation increased the stability of capsanthin against low/medium moisture, heat, and especially light, but was less effective in protecting capsanthin microcapsules in high moisture. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39671.     

A comparative study of analytical methods for evaluation of soybean oil quality

This study is focused on the improvement of soybean oil stability by addition of additives and blending with more stable oils. The methods for evaluation of oil deterioration include changes in dielectric constant (DC), total polar (TP) compounds, refractive index (RF), fritest (FT), acid value (AV), iodine value (IV), anisidine value (AnV), carbonyl value (COV), viscosity and color. Statistically significant correlations were obtained between changes in DC and increase in the TP compounds, RF, FT, AV, AnV, COV and the decrease in the IV, respectively. Food oil sensor reading of 4 as a measure of changes in DC of oil has been suggested as the criterion of low oil quality. Consequently, the cut-off level for straight and blended soybean oils were thereby identified by using the above parameters. To whom correspondence should be addressed at: Food Industry Research and Development Institute, P.O. Box 246, Hsinchu 30099, Taiwan, R.O.C.     

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.     

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.     

黄豆蛋白改性腈纶的研制

采用丙烯腈对黄豆蛋白进行疏水改性后,将其与聚丙烯腈共混纺丝,用常规腈纶的生产工艺纺制吸湿和吸水性良好的黄豆蛋白改性腈纶。采用黄豆蛋白质量分数为33％的改性黄豆蛋白与常规聚丙烯腈原液共混纺丝,当黄豆蛋白质量分数为10％时,获得的改性腈纶断裂强度2.75 cN／dtex,断裂伸长率25.4％,回潮率1.7％,保水率8.3％。     

实施全过程煤质管理 提高煤炭产品质量

开滦集团公司通过建立完善的质量保证体系;实施有效的煤炭质量管理、考核措施,奖罚严明;推广市场化精细管理;保证了煤炭产品的质量,树立了开滦集团良好的企业形象。     

Analysis of flavor quality and residual solvent of soy protein products

A simple, direct, gas Chromatographic technique is described for eluting and resolving residual solvent and flavor-related volatile components from soy products such as flour and protein isolates. No prior enrichment of volatiles is necessary. A sample, together with a small amount of water, is secured in a glass liner and placed in the heated injection port of a gas Chromatograph. The volatiles are rapidly steam distilled from the sample by the heat, moisture, and flow of carrier gas and are adsorbed on the chromatographic column in situ. Residual solvent and other volatiles adsorbed on the column are resolved by temperature-programmed gas chromatography and identified by combined gas chromatography-mass spectrometry. The correlation between taste panel flavor score and concentration of volatile components is significant at the 1% level. Presented at the AOCS Meeting, New York, May 1977.     

Oxidative stability of soybean oil products obtained by regioselective chemical interesterification

Oxidative stability of products produced as potential margarine basestock from soybean oil and methyl stearate by a novel chemical regioselective interesterification was evaluated. The oxidative stability of the products was evaluated by peroxide formation and volatile analysis during storage in the dark with oxygen at 60°C for 72 h. The product obtained by regioselective interesterification resulted in the lowest peroxide formation and volatile concentration sample in comparison with soybean oil and the randomized product of the regioselective interesterified product. Regioselective interesterification of soybean oil with methyl stearate produced a product with increased oxidative stability. Presented at 84th American Oil Chemists’ Society Annual Meeting, April 26–30, 1993, Anaheim, California.