基于两步法研究盐离子预聚集对大豆分离蛋白凝胶性的影响

Effect of Pre-Aggregation with Different Salt Ions on Gel Properties of Soy Protein Isolate Based on Two-Step Gelation Method

摘要:

为了改善大豆分离蛋白(soy protein isolate,SPI)凝胶品质,提出了一种两步制备凝胶的新方法:首先利用3种不同浓度(0~15mmol/L)的硫酸盐(CaSO₄、MgSO₄和ZnSO₄)对SPI进行预聚集处理,然后通过添加CaSO₄至盐离子总浓度为35mmol/L使蛋白质凝胶化,并探讨了不同盐离子预聚集对SPI结构及凝胶特性的影响。结果表明:盐离子与蛋白质分子之间的相互作用是自发的吸热反应,由熵变驱动,滴定ZnSO₄引起的热量变化较CaSO₄和MgSO₄更为剧烈；盐离子的加入引起了SPI α-螺旋结构含量上升,β-折叠结构含量下降及荧光强度降低。在同一浓度条件下,经ZnSO₄诱导的SPI聚集体颗粒的粒径、表观黏度均显著大于其他两种盐离子(P<0.05),说明Zn²⁺的聚集能力更强。流变性分析结果表明,相较于未经预聚集处理的SPI凝胶,经10.0mmol/L CaSO4、10.0mmol/L MgSO₄、5.0mmol/L ZnSO₄预聚集处理的SPI凝胶的弹性分别提高了49.5%、30.0%和59.9%,但蛋白质分子过度预聚集会导致凝胶强度的下降。利用不同盐离子对SPI进行适当预聚集处理能够有效提高蛋白质凝胶性能,研究结果旨在为SPI凝胶制品质构性质的改良提供一种绿色、简洁的新思路。

Abstract:

In order to improve the gel quality of soy protein isolate (SPI), a new two-step gel-preparation process was applied in this study. First, SPI dispersions were pre-aggregated by using three sulfates (CaSO₄, MgSO₄, and ZnSO₄) at different concentrations (0~15mmol/L) and then gelled by adding CaSO₄ up to a total salt concentration of 35mmol/L. The pre-aggregation effects of different salt ions on the structure and gelation of SPI were investigated. The results showed that the interaction between salt ions and protein molecules was a spontaneous endothermic reaction driven by entropy change, and the heat change caused by titration of ZnSO₄ was more intense than that of CaSO₄ and MgSO₄. The addition of salt ions caused the increase in the content of α-helix, but decrease of β-sheet structure and fluorescence intensity. At the same addition level, the particle size and apparent viscosity of SPI aggregates induced by ZnSO₄ were significantly larger than those induced by the other two salt ions (P<0.05), indicating that Zn²⁺ had stronger aggregation ability. The rheological results showed that compared with SPI gel without pre-aggregation, the elastic modulus of the SPI gel prepared by pre-aggregation with 10.0mmol/L CaSO₄, 10.0mmol/L MgSO₄ and 5.0mmol/L ZnSO₄ were increased by 49.5%, 30.0% and 59.9%, respectively. However, excessive aggregation of protein molecules led to the decrease in gel strength. Therefore, proper pre-aggregation of proteins with different salt ions could effectively improve the gel properties. These results might provide a green and simple method for the texture improvement of SPI gel products.