| Soybean is the most important sources of protein for animals and humans. It contains healthful such substances as soyasaponin, isoflavone, fibrin, unsaturated fatty acid, etc. are medicinally healthful. However, raw beans contain a number of antinutritional factors (ANFs), such as trypsin inhibitors, lectin and allergic proteins, producing adverse effects on the animal growth and health. It is usual to subject the raw soybean to some types of heat treatments. But the prolonged high temperature treatment required to destroy all ANFs is likely to damage the availability of certain essential amino acids. Since some ANFs are chemically proteins, it seems that proteolysis is a promising approach to inactivate them.The effective activation techniques of TIA and its usage in food processing were systematically investigated in this trial. Seven in vitro trials and one in vivo trials were conducted, including: Investigation of the TIA in soybean products; activation of TIA by various protease; activation of TIA by Alcalase; The exploitation of SPI with low TIA; The processing properties of SPI with low TIA; The effect of SPI with low TIA on the growth in rats; The exploitation of nutritional soybean milk with low TIA and The exploitation of fermented soybean milk with low TIA.TIA in Hydrolysed Soybean Protein, Soybean Protein for Milk Use, Soybean Protein Textures and Tofu was activated more than 90%. There was nearly no TIA in Fermented Tofu and Soybean Sauce. TIA in Soybean Meal without Sugar, X X X Soybean powder, Soya milk and lactone bean curd were activated less than 90%. Pasteurization could activate 14. 07% of the TIA. High pressure sterilization can activate 91.1% while UHT 65.9%.The relative activation activity to TIA of Alcalase was the highest. The acidic protease was secondary. The neutral protease and papain had the weakest relative activation activity. DH of soybean protein rose rapidly within 5-10 minutes, and then the proteolysis rate slowed down. DH by the Alcalase was the highest 30 minutes later, reaching 16.34%.The optimum activation parameters of Alcalase was pH8. 88-9. 05, temperature 43. 40-44. 70 , the amount of Alcalase 10. 44~11. 29 L/g, substrate concentration 6. 5l-7. 18%, activation time 30min. The activation rate of TIA was high within the premier ten minutes, reaching 95. 01% and being unchangable 30 minutes later. The DH of soybean protein rose rapidly within the premier 10 minutes, reaching 10. 87%, and changed slowly from 10 to 50 minutes. It was nearly stable 50 minutes later, reaching about 20%.The activation rate to TIA of Alcalase rose with the increase of substrate concentration. It was the highest (76. 24%) when the substrate concentration was 7% and became stable when the substrate concentration was more than 7%. It remainedthe highest (75.40%) when the substrate concentration was 10%. The test results of SPI with low TIA. accorded to those of the best soybean products in our country. With the proteolysis time extended, the degree of the soybean protein cleavage became great, and the average molecular weight of the peptides decreased. The average molecular weight was 2135Da. There were different sizes of soybean peptides in the product, and the majority of peptides was in small and middle size. There were less intact soybean protein, big size of peptides and amino acid in the product.The NSI of the SPI with low TIA rose with the proteolysis time extended. It rose rapidly within the premier 5 minutes. The NSI at pH4. 5 improved remarkably than that at pH7. 0. The NSI of enzyme-modified SPIs was strongly correlated with their DH. The pH. -solubility curves were bell-shaped for all samples. The NSI was higher at alkaline pH than that at acidic pH. The foam property of SPI with low TIA (50mins) reached about 1. 71 times improvement than that of SPI. And it was 1. 07 times than that of the product (30 minutes). But the foam stability was lower than that of the SPI. Enzyme treatment was effective in increasing thermal aggregation of SPI, amounting to more th...
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