| Because of the limitations of structure, some functionalities of natural soybean protein can not meet the requirements of industrial production.The modification of soybean protein is very significant to enhance its functionality and to expand its application fields. In this paper, the preparation of soybean protein with good dispersibility?good emulsibility and good foamability by enzymatic modification and their application in food had been studiedFirstly, process conditions of the preparation of soybean protein with good dispersibility?good solubility and low viscosity was studied.It was concluded that when the protein content of substrate was 12%, hydrolysis pH was 7.0 and temperature was 40 ?, the optimum condition of preparation was enzyme adding amount 0.06% based on the solids content, reacting for 40min. Hydrolysates were heated at 110? for 10s to inactivate enzyme and spay dried, and then mixed with 1% phospholipid. Compared with imported protein GFJ,the final product had better solubility and similar impurity?dispersibility and viscosity.Using aminopeptidase and carboxypeptidase to modifiy soybean protein with good dispersibility to improve protein flavor. It was concluded that when the protein content of substrate was 12%, hydrolysis pH was 7.0 and temperature was 40 ?, the optimum hydrolysis time was 1h.When carboxypeptidase and aminopeptidase were used singly, the ideal adding amount was 0.06%, and when used in combination, the addition of two enzymes were 0.03%.When keep the same adding amount, aminopeptidase had better debittering ability than carboxypeptidase and the combined use of two enzymes had better debittering effect than any single enzyme.SPI was treated with controlled pH and temperature to make the specific component denatured, and the denatured component had been hydrolyzed by pepsin. The determination of emulifying properties showed that the hydrolysis of 11S could significantly improve emulsifying activity and emulsifying stability to 1.716,38.2 min from 0.724,25min, while the hydrolysis of 7S could only improve emulsifying stability to 29.6 min and the non-selective hydrolysis of 11S and 7S could only improve emulsifying activity to 1.417. Foaming capacity and foam stability of the hydrolysates were both significantly improved. All of the supernatant from hydrolysates centrifuged at pH 4.5 had more excellent foaming ability which was 3-4 times as high as unhydrolyzed protein. The foam stability of supernatant were different, protein with 7S component hydrolyzed was 86.88%, protein with 11S component hydrolyzed was only 76.88% and protein with 11S and 7S were both hydrolyzed was 81.76%.Using hydrolysate whose 11S component had been selectively hydrolyzed to prepare soy protein with good emulsibility.The product had excellent emulsifying activity of 1.716 which was better than sodium caseinate.While the emulsifying stability of them were close.The product had been used in coffee mate to replace sodium caseinate. When this self-made coffee mate was added in blake coffee, the coffee system was uniform, stable and thick, and the bitterness and sour of black coffee had been reduced.But because of its beany flavor,it had some negative impact on the taste.Using hydrolysate whose 11S and 7S component were both hydrolyzed to prepare soy protein with good foamability by one-step and two-step method. The results showed that the foaming capacity and foam stability of products prepared by two methods were 260mL?83.1% and 265mL?85.28%, which were very close. But when use the one-step method,the yield of supernatant from hydrolysate centrifuged at pH 4.5 was higher.The product had been used in sponge cake to replace egg white and egg.After replacement, the whipping time had be shortened to less than 10min from 20min.When 50% or 75% egg white or 50% egg were replaced, the quality of cake was similar to or even more excellent than normal sponge cake. When the replacement was too big, the quality of cake was deteriorate and meanwhile sticky taste and bean flavor would apeared. |
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