蛋白质氧化对乳清分离蛋白功能性质的影响

为了进一步研究蛋白质氧化对乳清分离蛋白(WPI)功能性质及流变学性质的影响,试验采用两种不同浓度的氧化系统H2O2(1 mmoL/L~20 mmoL/L)和FeCl3浓度(0.1 mmoL/L~2 mmoL/L)对WPI分别氧化1 h、3 h、5 h,测定其性质。结果表明:20 mmoL/L的H2O2氧化WPI 5 h,其乳化活性下降了50%以上;1 mmoL/L FeCl3氧化WPI 3 h,其凝胶硬度降低了94.5%;20 mmoL/L H2O2与1mmoL/L FeCl3氧化WPI 3 h,其弹性从0.976下降到0.713和0.721,分别降低了26.9%和26.1%;当H2O2浓度20 mmoL/L时,弹性模量从8154 Pa降到5399 Pa,复合模量从10890 Pa降到6653 Pa,分别降低了33.79%和38.91%;当FeCl3浓度为1 mmoL/L时,弹性模量从8154 Pa降到4935 Pa,复合模量从10890 Pa降到6049 Pa,分别降低了39.47%和44.45%。长时间高浓度的氧化条件使得蛋白质的空间结构受到严重影响,WPI的功能性质及凝胶质地发生较大的变化。因此,在实际生产中应尽可能地控制蛋白氧化的发生,减少其因为氧化所带来的营养损失或者降低其应用价值。

Effect of Protein Oxidation on Functional Properties of Whey Protein Isolates

The objective of this study was to explore the effect of protein oxidation on the functional and rheological properties of whey protein isolate (WPI). There were two different oxidation systems containing H2O2 (1 mmoL/L~20 mmoL/L) and FeCl3 (0.1 mmoL/L~2 mmoL/L) in this experiment. WPI was treated by the oxidation systems for 1 h, 3 h and 5 h respectively. The result revealed that the emulsifying activity of WPI decreased over 50% under the condition of 20 mmoL/L H2O2 for 5h. The gel hardness decreased 94.5% owing to 1mmoL/L FeCl3 for 3 h. Additionally, results also showed that the elasticity of WPI was decreased from 0.976 to 0.713 and 0.721 respectively by 20 mmoL/L H2O2 for 5 h and 1 mmoL/L FeCl3 for 3 h treatment. In addition, 20 mmoL/L H2O2 led to the decrease of elastic modulus value of WPI decreased from 8154 Pa to 5399 Pa and decrease of the complex modulus value from 10890 Pa to 6653 Pa. When 1 mmoL/L FeCl3 was used, the elastic modulus value declined from 8154 Pa to 4935 Pa and the complex modulus value was reduced from 10890 Pa to 6049 Pa. The spatial structure of proteins severely affected at the long time oxidizing conditions of high concentration. Therefore the functional properties and the gel texture of WPI were damaged significantly. Thus, protein oxidation should be avoided as much as possible in actual production for maintaining the nature characteristics of WPI, thereby preventing nutrient losses and promoting application value .