苯丙氨酸添加下酪蛋白类蛋白反应修饰物的抗氧化性质

In vitro antioxidant activity of the casein hydrolysates modified by plastein reaction in the presence of phenylalanine

采用木瓜蛋白酶水解酪蛋白制备水解度为9.6%、DPPH·清除率为38.7%的水解物,添加苯丙氨酸于水解物并利用响应面法优化木瓜蛋白酶催化的类蛋白反应条件。在反应时间固定为5h下得到适宜的条件为:温度30℃、底物浓度50%(w/v)、酶添加量3kU/g蛋白质、氨基酸添加量0.74mol/mol水解物游离氨基。此条件下分别制备出5个修饰产物,以不添加苯丙氨酸的修饰产物或水解物和苯丙氨酸混合物为对照,评价它们的抗氧化活性。结果表明,与酪蛋白水解物或混合物或不添加苯丙氨酸的修饰产物相比,添加苯丙氨酸的修饰产物的DPPH·清除能力、还原能力和·OH清除能力显著提高;但是抗氧化性质与所采用的氨基酸添加量、反应时间之间的关系不显著。

Papain was used to hydrolyze casein to prepare casein hydrolysates with a degree of hydrolysis of 9.6% and a scavenging activity on DPPH- radical of 38.7%. Phenylalanine was added into the hydrolysates to carry out a plastein reaction catalyzed by papain. When reaction time was fixed at 5h,response surface method was used to optimize plastein reaction conditions,which were selected as follows： reaction temperature 30℃,substrate concentration of 50% （w/v）,enzyme addition 3kU/g proteins,phenylalanine addition 0.74mol/mol free amino groups of the hydrolysates. Five modified casein hydrolysates were thus prepared and evaluated for their antioxidant properties,with the original casein hydrolysates,mixture of casein hydrolysates and phenylalanine,modified casein hydrolysates without phenylalanine addition as controls. The evaluation results showed that the modified casein hydrolysates had better antioxidant properties including scavenging activity on DPPH~ radical or hydroxyl radical and reducing powder,compared to these controls. It was also found that the improved antioxidant properties of the modified casein hydrolysates were not related to the reaction time and phenylalanine addition applied in the preparation.