转谷氨酰胺酶对大豆分离蛋白乳状液冻融稳定性的影响

采用转谷氨酰胺酶（transglutaminase，TGase）改性提高大豆分离蛋白（soybean protein isolate，SPI）乳状液冻融稳定性。以出油率和分层系数为稳定性指标，研究TGase交联时间、添加量、冻融循环次数对SPI乳状液冻融稳定性的影响。通过显微结构、热特性分析比较研究由SPI、TGase改性SPI作为乳化剂乳状液的冻融稳定性，利用十二烷基硫酸钠-聚丙烯酰氨凝胶电泳分析酶改性对SPI组成的影响，进而分析与乳状液稳定性的关系。结果表明：经过3 次冻融循环后改性SPI制备的乳化剂仍保持较好的冻融稳定性，TGase交联时间3 h、添加量1.5%时稳定性较好，微观结构可看出改性SPI乳状液处于相对稳定状态。乳状液冻融过程中热特性的差异，反映出改性蛋白在冻融过程中乳状液结晶及融化的热行为得到了改变。十二烷基硫酸钠-聚丙烯酰氨凝胶电泳结果表明酶改性使蛋白组成发生改变，从而影响大豆蛋白的冻融稳定性。TGase改性大豆蛋白具有较好的冻融稳定性，为其在冷冻食品中应用提供理论依据。

Effect of Transglutaminase on Freeze-Thaw Stability of Soybean Protein Isolate Emulsion

In this study, transglutaminase (TGase) was used to improve the freeze-thaw stability of oil-in-water emulsion stabilized by soybean protein isolate (SPI). We evaluated the influence of TGase reaction time, enzyme dosage and the number of freeze-thaw cycles on the freeze-thaw stability of SPI-stabilized emulsion as reflected by oiling off and creaming index. Meanwhile, the microstructure and thermal characteristics of the emulsions containing SPI and TGase-modified SPI as emulsifier were compared, and the effect of TGase modification on SPI composition was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Furthermore, the relationship between enzymatic modification and emulsion stability was analyzed. The results show that after three freeze-thaw cycles, the emulsion containing TGasemodified SPI maintained good stability. A crosslinking time of 3 h and an enzyme dosage of 1.5% were found to be optimal conditions to obtain better freeze-thaw stability. The emulsion remained stable as indicated by its microstructure. The changes in thermal properties during freeze-thaw showed that the crystallization and melting behavior of the emulsion altered. SDS-PAGE revealed that SPI composition changed after enzymatic modification, thus affecting the freeze-thaw stability of the emulsion. This study provides a theoretical foundation for applying TGase-modified SPI in frozen food.