不同杀菌处理方式对SPI冻藏过程中理化特性的影响

Effects of Different Sterilization Conditions on Physicochemical Properties of SPI during Frozen Storage

为了研究不同杀菌条件对SPI理化特性的影响及相应SPI溶液冷冻条件下的物化性质变化,通过65℃、90℃和UHT不同杀菌处理所得SPI(分别记为65SPI、90SPI和USPI)制备相应蛋白溶液,经-18℃冻藏后,对其理化特性进行分析研究。试验结果表明:3种杀菌处理均造成了SPI一定程度的变性,与冻前未处理SPI相比,90SPI和65SPI溶液的可溶蛋白含量和表面巯基显著降低,粘度、粒径大幅增加,USPI则未有明显变化。此外,90SPI和USPI的疏水基团暴露程度较高,非还原电泳显示其AB亚基发生解离;不同杀菌处理SPI其溶液在冻藏期间内,随冻藏时间延长,蛋白溶解度、粘度、表面巯基和总巯基数量呈下降趋势,粒径和疏水基团暴露程度增加。冻藏后蛋白电泳图谱显示,65SPI和90SPI通过二硫键形成了分子量较大的可溶性聚集体。

The effects of different sterilization conditions on the physicochemical properties of soybean protein isolate（ SPI） during frozen storage were studied to gain scientific knowledge and provide basis for supplying soy foods with good quality. SPI was prepared after sterilized at 65℃,90℃ and UHT（ denoted as 65 SPI,90SPI and USPI）, respectively. The changes of physicochemical properties of protein dispersions（ 2%,p H value 7. 0） subjected to frozen storage at- 18℃ were investigated. The results showed that three types of sterilization all resulted in heat denaturation of proteins. Compared with control SPI,the soluble proteins content and free SH groups of 90 SPI and 65 SPI were dropped sharply while the viscosity and particle size were increased greatly. However,there were no marked changes of USPI. In addition,hydrophobic domains of 90 SPI and USPI were exposed to a higher extent and their AB subunits were in dissociation state according to non-reducing SDS-PAGE. SPI with different sterilization treatments underwent different chemical and physical changes during frozen storage. The solubility,viscosity,free and total SH groups of protein trended down gradually with the increase of frozen time,while particle size and exposed extent of hydrophobic domains were increased during frozen storage. Some soluble aggregations associated with disulfide bonds were observed in the SDS-PAGE electrophoresis of 65 SPI and90SPI solutions after frozen storage.