无机盐对木瓜蛋白酶凝固大豆分离蛋白凝胶的影响

Effect of Inorganic Salts on Papain-Induced Coagulation of Soybean Protein Isolate

为研究食品中常见无机盐对木瓜蛋白酶凝固大豆分离蛋白凝胶的影响,以大豆分离蛋白(SPI)为原料,测定添加NaCl、KCl、CaCl2、MgCl2和MgSO4等常见无机盐后木瓜蛋白酶凝固SPI的时间、凝胶质构、凝固过程中pH值及蛋白质降解程度的变化。结果表明:添加一定浓度的无机盐可以缩短凝固时间并提高凝胶强度。相同离子强度下,Ca2+和Mg2+对凝固时间及凝胶强度影响均大于Na+和K+。添加无机盐可使SPI的pH值降低,加酶后pH值再次持续下降,但一定时间后趋于稳定。无机盐的种类和浓度对木瓜蛋白酶凝固SPI过程中蛋白质降解程度影响不明显。SPI中CaCl2的离子强度为15(CaCl2浓度为5mmol/L)时,将酶添加量从0.15%减少到0.1%,可使凝胶强度提高60%。因此,添加适量的一价及二价无机盐可显著缩短酶凝固时间并提高凝胶强度。添加Ca2+和Mg2+等二价阳离子盐类是提高木瓜蛋白酶凝固大豆蛋白凝胶强度的有效途径。

In order to explore the effect of inorganic salts on papain-induced coagulation of soybean protein, the changes of clotting time, texture properties, pH and protein degradation were determined during or after the coagulation of soybean protein isolate （SPI） in the presence of one of five salts including NaC1, KC1, CaCl2, MgCl2 and MgSO4. The results showed that the clotting time was shortened and gel strength was increased; the pH of SPI was reduced after the addition of salts. After papain was added, the pH revealed a continuous decrease to a steady level upon a certain time of incubation. Ca^2＋ and Mg^2＋ revealed more effective than Na^＋ and K^＋ on both clotting time and gel strength under the same ionic strength. The gel strength revealed an increase by 60% when the amount of papain was reduced to 0.1% from 0.15% （m/m）. Therefore, the presence of salts could shorten clotting time and gel strength, and the addition of calcium or magnesium salts is an effective way to enhance the strength of oanain-induced SPI gel.