Optimized preparation of ACE-inhibitory and antioxidative whey protein hydrolysate using response surface method

Abstract

The main aim of the present study was to optimize the hydrolysis conditions of whey protein isolate digested by a protease preparation from Aspergilus oryzae through response surface method (RSM) in order to achieve the maximum angiotensin I-converting enzyme (ACE)-inhibitory activity and antioxidant properties. The effects of hydrolysis conditions including time (2, 13, 24, 35, and 46 h), temperature (40, 45, 50, 55, and 60 °C) and pH (6, 6.5, 7, 7.5, and 8) were investigated on the bioactivity of whey protein hydrolysates. Each process parameter emerged to have a dual effect on bioactivity; that is, increase in all variables promoted bioactive peptide generation through facilitating enzyme access to the primary protein sequence by partial unfolding of the compact globular assemblies of whey proteins. However, prolonged digestion at high temperatures and alkaline pH were concomitant with decreased bioactivity which are attributed to hydrolysate aggregation and splitting of bioactive peptides into biologically inactive counterparts, respectively. Nonetheless, some discrepancies were observed between the trend of ACE-inhibitory activity and that of antioxidant activity changes which was explained in light of their general characteristics. RSM efficiently identified the critical levels of each variable to obtain maximum bioactivity. It was shown that hydrolysate prepared at 56.54 °C and pH 6.04 resulting from digestion for 3.89 h exerted 74% ACE-inhibitory activity, 666.31 μM trolox equivalent/mg antioxidant activity, and 14.03% hydrolysis degree.

摘要:

本文采用响应面法对米曲霉蛋白酶水解乳清分离蛋白的条件进行优化,以取得最大的血管紧张素转化酶(ACE)抑制活性和抗氧化特性。研究了水解时间(2, 13, 24, 35 和46 h)、温度(40, 45, 50. 55 和 60 °C) 和 pH (6, 6.5, 7, 7.5 和8)对乳清蛋白水解物生物活性的影响。每个工艺参数对生物活性会产生双重影响,也就是增加所有变量,通过将致密的球状乳清蛋白部分折叠解开使酶进入一级蛋白序列,从而促进生物活性肽的产生。然而,在高温和碱性pH条件下,延长水解时间会降低水解物的生物活性,主要原因是随着水解时间的延长,水解物聚集以及生物活性肽裂解成没有生物活性的物质。虽然如此,血管紧张素转化酶(ACE)抑制性和抗氧化活性会出现不一致,这由于两者的特性不同。响应面法(RSM)能够有效地确定并获得最大生物活性的每个变量的水平。实验结果表明:在56.54 °C,pH 6.04 水解时间为3.89 h得到的水解物具有74%的血管紧张素转化酶(ACE)抑制活性,等效抗氧化活性为666.31 μM,水解度为14.03%。