自由基氧化引起乳清蛋白溶解性、凝胶强度和乳化性变化的研究

Study on the solubilizing,gelling and emulsifying properties of whey protein isolate modified by a free radical-generating system

主要研究了在羟基自由基氧化体系中,不同H2O2浓度(1～20mmol/L)及不同FeCl3浓度(0.1～2mmol/L)对乳清蛋白溶解性、凝胶强度和乳化性等功能特性的影响。每种氧化条件的氧化时间分别为1、3、5h。结果表明:氧化对蛋白功能性起着很大的破坏作用,同未氧化的对照组乳清蛋白相比,氧化后乳清蛋白在所有氧化条件下,溶解性降低超过35%、凝胶强度降低达85%以上,在不同的氧化剂浓度下,5h氧化后乳清蛋白的乳化性均降低达60%以上,FeCl3浓度的改变对功能性的破坏更大。并且发现,溶解性的降低直接影响着蛋白的凝胶性和乳化性。总之,氧化会破坏蛋白质的结构,降低乳清蛋白的功能特性,但是适当的氧化可以提高乳化性。在实际生产中应该合理控制蛋白氧化的发生。

The objective of the present study was to investigate the changes in solubility, gel-forming ability and emulsifying capability of whey protein isolate （WPI） after exposures to a hydroxyl radical-generating system （HRGS） in different concentrations of H2O2 （1～20mmol/L） or FeCl3 （0.1～2mmol/L）for 1 ,3,5h.The results showed that oxidation reduced solubility （up to 35%） and gel strength （up to 85%） under the oxidative conditions investigated.The deleterious effect was greater by FeCI3 than by H202.However, while extensive protein oxidation impaired emulsification of WPI, mild oxidation with low concentrations of the oxidants and short oxidizing times favored emulsion formation and enhanced the emulsion stability in the WPl-oil system.The gelation and emulsifying ability of WPI were closely related to protein solubility but the gelation was more sensitive to the solubility change. The overall effect of HRGS on the functionality of WPI appeared to depend on the extent of physicochemical modification of the proteins.