脱酰胺处理对不同谷物蛋白体外消化率的影响

Effect of Deamination on the in vitro Digestibility of Grain Proteins

脱酰胺处理是蛋白质改性一种方式,经脱酰胺后,蛋白的理化性质和营养性质都会发生改变。本实验研究了酸法脱酰胺处理对大米、小麦、玉米蛋白体外消化率的影响,并从蛋白质的溶解度、表面疏水性、巯基和二硫键含量以及超微结构等理化性质方面来探究脱酰胺影响体外消化率的作用机理。试验结果表明:随着脱酰胺程度的加大,大米蛋白、小麦蛋白和玉米蛋白质巯基和二硫键之间的相互转化不明显(P<0.05),两者的含量基本维持不变;三种谷物蛋白的溶解度在胃蛋白酶最适p H 1.5和胰蛋白酶最适p H 7的条件下逐渐增大;蛋白质的表面疏水性随脱酰胺度的增加逐渐减小;体外消化率也分别从原来的66.5%、79.5%和78.5%提高到了79.5%、89.0%、和89.2%,超微结构从原来的致密聚集变得多孔疏松,更利于蛋白质的消化。

Deamination is a method used to modify the physicochemical and nutritional properties of proteins. Here the effect of deamination using an acid method on the in vitro digestibility of rice, wheat, and corn proteins was studied. Additionally, the mechanism underlying the effects of the deamination on the in vitro digestibility of proteins in three types of grains was explored in terms of physicochemical properties including solubility, surface hydrophobicity, sulfhydryl and disulfide content, and ultrastructure. The results showed that with an increasing degree of deamination, the difference in the inter-conversion between sulfhydryl and disulfides in the proteins of the three types of grains(rice, wheat, and corn) was not significant(p < 0.05), and the sulfhydryl and disulfide contents were generally unchanged. Protein solubility in the three types of grains at the optimum p H for pepsin(p H = 1.5) and trypsin(p H = 7.5) was slightly increased; however, surface hydrophobicity slightly decreased with an increasing degree of deamination. The in vitro digestibility of rice, wheat, and corn proteins increased from 66.5% to 79.5%, 79.5% to 89.0%, and 78.5% to 89.2%, respectively. Meanwhile, the protein ultrastructure, which was originally dense and compact, became porous and loose, which was more conducive to digestion.