抗冻融大豆蛋白的制备

Preparation of Soy Protein with High Freeze-Thaw Stabilization

采用湿法美拉德反应对大豆蛋白进行糖基化改性，研究了糖基化接枝产物的冻融稳定性。结果表明，湿法糖基化大豆蛋白能有效提高接枝产物的冻融稳定性，在SPI（大豆分离蛋白）浓度40mg／mL、蛋白与糖质量比1：3、反应时间4h、pH8．0、反应温度95℃条件下的接枝物冻融前后的EAI（乳化活性）分别是未改性蛋白的1．69倍和1．76倍，ESI（乳化稳定性）是未改性蛋白的1．37倍和1．27倍。傅里叶红外光谱分析表明，SPI—D接枝物在1000cm^-1附近有较强的吸收，在3700～3200cm叫处有一个更宽的振动伸缩吸收，葡聚糖以共价键的形式接入到SPI上。SPI—D接枝物在激发波长为347nm，发射波长在435nm处有最大的荧光强度，符合美拉德反应产物的荧光特性，进一步证明SPI与葡聚糖发生了美拉德反应。

Soy protein isolatedextran graft reaction products have been prepared by Maillard reaction on the wet - heating condition, and the freeze - thaw stabilization of conjugates has been studied in the paper. The results indicated that the high freeze - thaw stabilization of soy protein isolate can be improved through Maillard reaction. The optimum conditions are as follows ： soy protein isolate concentration 40 mg/mL, the weight ratio of soy protein isolate and dextran 1： 3, reaction time 4 h, pH 8.0, and reaction temperature 95 ℃. Compared with the previously unmodified soy protein isolate, the emulsifying activity index （EAI） of before and after freezing and thawing were increased by 1.69 and 1.76 times respectively, and the emulsion stability index （ESI） were increased by 1.37 and 1. 27 times respectively. Fourier transform infrared spectroscopy （ FT - IR） analysis showed that compared to soy protein, soy protein isolate - dextran conjugates in 3 700 - 3 200 cm ^- 1 stretching vibration presented a wider absorption. SPI -D also showed a strong absorption at 1 000 cm^- 1 and soy protein isolate was grafted with dextran molecules by covalent bonds. The conjugates had the strongest florescence intensity on condition of emission of 347 nm, the excitation of 435 nm and it was conformed to the fluorescence characteristics of Maillard reaction products. All data showed that the complex of the soy protein and dextran had been produced by the reaction.