Soybean nutritional improvement

In practice, mainly soybean protein, gluten, and milk proteins have been nutritionally improved by incorporation of essential amino acids (Leu, Lys, Met) into the peptide chains. Amino acids to be... 

The nutritional value of a proteia can be improved by the addition of amino acids of low abundance ia that proteia. Thus the fortification of plant proteias such as wheat, com, and soybean with L-lysiae, DL-methionine, or other essential amino acids (L-tryptophan and L-threonine) is expected to alleviate some food problems (11). Such fortification has been widespread ia the feedstuff of domestic animals. 

Pea.nuts, The proteins of peanuts are low in lysine, threonine, cystine plus methionine, and tryptophan when compared to the amino acid requirements for children but meet the requirements for adults (see Table 3). Peanut flour can be used to increase the nutritive value of cereals such as cornmeal but further improvement is noted by the addition of lysine (71). The trypsin inhibitor content of raw peanuts is about one-fifth that of raw soybeans, but this concentration is sufficient to cause hypertrophy (enlargement) of the pancreas in rats. The inhibitors of peanuts are largely inactivated by moist heat treatment (48). As for cottonseed, peanuts are prone to contamination by aflatoxin. FDA regulations limit aflatoxin levels of peanuts and meals to 100 ppb for breeding beef catde, breeding swine, or poultry 200 ppb for finishing swine 300 ppb for finishing beef catde 20 ppb for immature animals and dairy animals and 20 ppb for humans. 

Soybean Protein Isolates. Soybean protein isolates, having a protein content of >90 wt%, are the only vegetable proteins that are widely used in imitation dairy products (1). Most isolates are derived from isoelectric precipitation, so that the soybean protein isolates have properties that are similar to those of casein. They are insoluble at thek isoelectric point, have a relatively high proportion of hydrophobic amino acid residues, and are calcium-sensitive. They differ from casein in that they are heat-denaturable and thus heat-labile. The proteins have relatively good nutritional properties and have been increasingly used as a principal source of protein. A main deterrent to use has been the beany flavor associated with the product. Use is expected to increase in part because of lower cost as compared to caseinates. There has been much research to develop improved soybean protein isolates. 

L. Chen, W. A. Dick, J. G. Streeter, and H. A. Hoitink, Fe chelates from compost microorganisms improve Fe nutrition of soybean and oat. Plant Soil 200 139 (1998). 

More details of the plastein reaction and its application to remove pigments such as chlorophyll, or to remove off-flavor components such as the beany taste of soybeans, are shown in Figure 2. The protein of the food system is solubilized and denatured (in order to achieve proteolysis), a protease is added, and the hydrolytic reaction is allowed to proceed. On partial hydrolysis of the protein the pigments and flavor constituents are released from the protein they are removed, the hydrolyzate is concentrated, and resynthesis and/or rearrangement of the amino acid sequence of the polypeptides is catalyzed by the same or a different protease. Resynthesis also can be carried out in the presence of added amino acid esters in order to improve the nutritional/functional properties of the protein. 

Such chemical changes may lead to compounds that are not hydrolyzable by intestinal enzymes or to modifications of the peptide side chains that render certain amino acids unavailable. Mild heat treatments in the presence of water can significantly improve the protein s nutritional value in some cases. Sulfur-containing amino acids may become more available and certain antinutritional factors such as the trypsin inhibitors of soybeans may be deactivated. Excessive heat in the absence of water can be detrimental to protein quality for example, in fish proteins, tryptophan, arginine, methionine, and lysine may be damaged. A number of chemical reactions may take place during heat treatment including decomposition, dehydration of serine and threonine, loss of sulfur from cysteine, oxidation of cysteine and methio-... 

The importslnce of lipoxygenase increases when soybean flour is added to wheat flour to improve baking quality or when soybean flour is admixed in larger quantities to improve the protein nutritional quality. 

New nutrition-oriented salad and cooking oils have been developed in recent years. LoSatSoy is an oil low in saturated fatty acids that was developed at Iowa State University, licensed to Pioneer Hybrid International (Johnston, lA), and commercialized as a salad or cooking oil. This specialty soybean oil has one-half the amount of saturated fatty acids in normal soybean oil (7% versus 15%) therefore, it is promoted as having improved nutritional and health benefits. 

Poultry. Lecithin has nutritional application in poultry feeds. The caloric value of lecithin (8900 kcal/kg) for broilers was reported to be greater than tallow (5000-7000 kcal/kg) or soybean oil (8800 kcal/kg) (332). This research was complementary to earlier observations that fat utilization and metabolizable energy value were improved when lecithin was also included in chick diets (333, 334). Phospholipids can increase pigment absorption contributing to egg yolk pigmentation (335). Nutrition also plays a key role in the value of meat. Brazilian research found that lecithin in the diets of broilers improved the sensory scores for breast meat (336). 

The use of sunflower meal is often limited by its availability. Adequate volumes, available on a sustained and consistent basis, would ensure a high utilization of sunflower meal in animal nutrition. Despite its dark appearance, lower energy, and higher fiber content, as compared to soybean meal, sunflower meal is a competitive product with potential for continued improvement through the use of tail-end screening to further reduce its fiber content (40). 

Legume seeds contain a number of antinutritive components, mainly lectin and trypsin inhibitors. The efficiency of the nutritional utilization of diets containing soybean is well below that expected on the basis of chemical composition [196]. In order to reduce the extent of this constraint, at present, all soy products go through expensive heat treatment or other processing procedures that can lead to losses of essential amino acids and to the production of toxic by-products. It is hoped that an effective strategy will help improve the nutritional value of soy proteins [197,198]. 

Fatty Acid Modifications to increase Soybean Oii Stabiiity, Enhance Oii/Fat Function, and/or improve Nutrition... 

Sebastian, S.A. P.S. Kerr R.W. Pearlstein W.D. Hitz. Soybean germplasm with novel genes for improved digestibility. Soy in Animal Nutrition Drackely, Ed. Federation of Animal Sciences... 

Kitamura, K. Genetic improvement of nutritional and food process quality in soybean. ]ap. Agric. 

---