模拟胃肠道消化对大豆低聚肽结构及抗氧化作用的影响

Effects of Simulated Gastrointestinal Digestion on Structure and Antioxidant Activity of Soybean Oligopeptides

大豆低聚肽是一种有益健康的功能性配料,所呈现的健康益处高度依赖于肽结构。采用紫外全波长扫描法及圆二色光谱法分析其结构是如何受胃蛋白酶、胰蛋白酶以及先胃蛋白酶后胰蛋白酶处理的影响。为探讨消化处理前、后大豆低聚肽抗氧化能力的变化规律,分别计算消化前、后大豆低聚肽的ABTS自由基清除能力、DPPH自由基清除能力、氧自由基吸收能力(ORAC)和铁离子还原能力(FRAP)。结果显示:大豆低聚肽主要为分子质量<1000 u的组分,经胃蛋白酶、胰蛋白酶及先胃蛋白酶后胰蛋白酶处理后<1000 u的组分比例最大可达88.46%。在波长275 nm处均有最大吸收峰。二级结构中,4组大豆低聚肽中无规则卷曲所占比例均为30%左右,约占总二级结构组成的1/3,表明了大豆低聚肽无序性较高且结构疏松开放。大豆低聚肽的ABTS自由基清除能力和铁还原能力稳定性均较好。经胰蛋白酶消化后,DPPH自由基清除率有所降低,氧自由基吸收能力极显著提高(P<0.01)。

Soybean peptides(SOPs)are functional ingredients with good health benefits.The health benefits presented are highly dependent on the peptide structures.SOPs were prepared from soybean protein isolate by hydrolysis.Ultraviolet full wavelength scanning method and circular dichroism spectrophotometry were used to analyze whether the structure of SOPs was affected by pepsin,trypsin and the sequential treatment of pepsin and trypsin.ABTS free radical scavenging ability,DPPH free radical scavenging ability,oxygen radical absorbance capacity(ORAC)and ferric ion reducing antioxidant power(FRAP)of SOPs were measured in order to explore the changes of antioxidant capacity of SOPs before and after digestion.The results showed that SOPs were mainly composed of components with molecular weight less than 1000 u,and the proportion of components less than 1000 u increased after digestion,and the maximum proportion reached 88.46%.They all had maximum absorption peaks at 275 nm.In the secondary structure,the proportion of random curl in the four groups of SOPs was about 30%,accounting for about 1/3 of the total secondary structure composition,indicating high disorder and loose and open structure of SOPs.The ABTS free radical scavenging ability and iron reducing ability of SOPs were stable.After trypsin digestion,DPPH radical scavenging rate decreased and oxygen radical absorption capacity increased significantly(P<0.01).