| which contains many amino acids. As the byproduct of oil processing, soy protein has a large production in China. However, affected by its natural property, soy protein has a limited application in the food industry, only used in a few areas such as meat products. So how to make soy protein be used in food industry more widely become an issue to be solved immediately. Beverage industry is an important branch of food industry. Beverage is one of the most consumer goods in our daily lives,60-70% of which are acidic beverages. So if soy protein can be applied to acidic beverages, we can greatly broaden the applications of soy protein. As we all know, soy protein has a poor solubility under acidic conditions (pH3.0-4.5), which is also the pH area of acidic beverages. So this will lead to a limited application of soy protein in acidic drinks, such as fruit juice. This paper aims to solve the acid-soluble problem of soy protein, make it has a good solubility and transparency in acidic conditions (pH3.0-4.5) to be fit for the addition of acidic drinks. By the study of different factors which can affect acid-soluble property of soy protein, this paper has explored three kinds of methods to prepare acid-soluble soy protein. The following conclusions were drawn from this essay:(1) Effect of chitosan(CTS) on improving solubility of soy protein under acidic conditions is studied. Studies have shown that 5%(w/w)chitosan(500KDa) can make soy protein has an ascension from 30.05±1.25% to 81.28±0.98% in NSI and a decline of 89.32±1.07% in turbidity, and the variation is positively related with the content of chitosan. In addition, the hydrothermal treatment also has a significant effect on improving the solubility of acid-soluble soy protein. The hydrothermal treatment near the isoelectric point of soy protein can make it has an ascension from 26.76±1.54% to 72.19±0.67% in NSI.(2) Effect of combination treatment of phytase and acidic protease on improving solubility of soy protein under acidic conditions is studied. Studies have shown that NSI of soy protein in pH4.0 is 41.74±2.02% when treated by phytase, NSI is 29.64±1.56% when treated by acidic protease, and NSI is 81.84±1.84% when treated by the combination of the two enzymes. So the combination treatment has a better effect than separate. The acid-soluble protein made by this method has a better flavor and taste.(3) At last, pre-gelatin method preparing acidic protein beverages is studied. Studies have shown that protein gelatin induced by GDL has a decline from 448.4±25.9nm to 282.7±21.6nm in average particle size after homogeneous treatment, and has a decline from 41.2±4.4mv to 15.8±2.4mv in zeta potential. Since forming more stable particles, soy protein has little precipitation during shelf life.(4)Based on laboratory test, this paper has carried out the pilot plant experiments, and applied this acid-soluble protein to the production of acidic beverages. The products have good stability and long shelf life, and related data and conclusions can provide a foundation for industrial mass production. |
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