大豆蛋白热变性程度对速溶豆腐花粉凝胶成型的影响

针对速溶豆腐花粉的制备工艺中需要对大豆进行热处理,热处理过程中大豆蛋白的热变性程度对豆腐花粉凝结的凝胶强度与凝结所需的时间具有显著影响,而现在速溶豆腐花粉的工业生产中还没有对豆浆热处理程度较为合适的标准。该文以大豆、大豆分离蛋白(soybean protein isolate,SPI)、大豆球蛋白(glycinin,11S)、β-伴大豆球蛋白(beta-conglycinin,7S)为原料,研究大豆蛋白热变性程度对速溶豆腐花粉凝胶成型的影响。研究表明11S比7S更难发生完全变性,SPI中的7S和11S比单独存在的7S、11S更难发生完全变性。传统制备方式、前热处理后喷雾干燥或冷冻干燥制备方式、先喷雾干燥或冷冻干燥后热处理制备方式对豆腐花凝结成型影响不同,其中传统方式制备的豆腐花凝胶效果最好,先干燥后热处理制备的豆粉凝胶效果比前热处理后干燥的豆粉好,引起豆腐花凝胶强度差异的主要原因是大豆蛋白中7S和11S热变性程度不同。制备同一凝胶强度的豆腐花,热处理温度越低,所需的热处理时间越长;制备高凝胶强度的豆腐花比制备低凝胶强度的豆腐花所能进行的热处理温度与时间范围小。大豆蛋白的7S处于完全变性而11S处于未完全变性的状态时,适合制备速溶豆腐花粉的大豆蛋白变性程度应控制热处理温度与时间范围为80℃时热处理20~65 min,85℃时热处理15~50 min,90℃时热处理10~35 min,95℃时热处理5~20 min。该研究结果为调控速溶豆腐花粉的凝胶特性提供理论依据。

Effects of heat denaturation degree of soybean protein on gel property of instant soybean curd

For the heat treatment of soybean is very necessary for the preparation process of instant soybean curd, the thermal denaturation degree of soy protein in the heat treatment process has significant influence on the gel formation strength and gel formation time in the gel forming of instant soybean curd, but there is no suitable standard for the heat treatment degree of soybean milk in the production process of instant soybean curd. In this paper, soybean, soybean protein isolate (SPI), glycinin (11S) and beta-conglycinin (7S) were used as raw material to investigate the gel formation property of instant soybean curd affected by different thermal denaturation degree of soybean protein in soybean. The study showed, the glycinin component was harder to be completely denatured than the beta-conglycinin component, and the beta-conglycinin component and the glycinin component in soybean protein isolate were harder to be completely denatured than the beta-conglycinin component and glycinin component separated from soybean protein isolate. The traditional preparation method, the pre-heat treatment and then spray drying or freeze-drying preparation method, the pre-spray drying or pre-freeze drying and then heat treatment preparation method of soybean curd had different effect on gel formation property. The study found that the traditional preparation of soybean curd had the best gel effect, and the pre-spray drying or pre-freeze drying and then heat treatment preparation of soybean curd had better gel effect than pre-heat treatment and then spray drying or freeze drying preparation of soybean curd. The main reason to the difference in gel strength of soybean curd was the different thermal denaturation degree of soybean protein in soybean, and the beta-conglycinin component and the glycinin (component in the soybean protein isolate had different thermal denaturation degree. When preparing the same gel strength of soybean curd, the lower temperature in the heat treatment needs longer time, and the higher temperature in the heat treatment needs shorter time. When obtaining higher gel strength of soybean curd, the heat treatment temperature and time range of soybean milk would be narrower than to obtain lower gel strength of soybean curd. When the beta-conglycinin component is fully denatured and the glycinin component is incompletely denatured, the suitable conditions for the degeneration degree of soybean protein for preparing instant soybean curd should be controlled as follows: the heat treatment temperate is 80 ℃ with the heat treatment time of 20-65 min, the heat treatment temperate is 85 ℃ with the heat treatment time of 15-50 min, the heat treatment temperate is 90 ℃ with the heat treatment time of 10-35 min and the heat treatment temperate is 95 ℃ with the heat treatment time of 5-20 min. The results of this study provide the important theoretical basis for regulating and controlling the gel characteristics of instant soybean curd.