角蛋白酶改性对大米蛋白水解产物起泡性质和结构特征的影响

本研究采用角蛋白酶对大米蛋白进行酶解改性，测定不同水解度大米蛋白水解产物的起泡性，氨基酸组成，并用聚丙烯酰胺凝胶电泳（SDS-PAGE）、圆二色谱和内源性荧光对其结构进行表征。结果表明，角蛋白酶能够显著提高大米蛋白在中性条件下的蛋白回收率（P < 0.05）。大米蛋白水解产物的起泡性随水解时间增加呈先增加后下降的趋势，起泡稳定性无显著性变化。相比未水解的大米蛋白，大米蛋白水解产物中甜味氨基酸、鲜味氨基酸含量显著增加（P < 0.05）。SDS-PAGE结果表明，大米蛋白水解产物主要由分子量低于20 kDa的多肽构成。相比未水解的大米蛋白，大米蛋白水解产物二级结构中的α螺旋和β折叠比例明显下降，而无规则卷曲比例显著增加（P < 0.05），这表明大米蛋白水解产物的二级结构更加柔性、松散。内源性荧光结果表明，经角蛋白酶水解后大米蛋白有更多的疏水性氨基酸暴露出来。本研究将为大米蛋白产品的开发和利用提供理论依据。

Effect of Keratinase Modification on the Foaming Properties and Structural Characteristics of Rice Protein Hydrolysate

In this study,rice protein(RP)was hydrolyzed by keratinase,and partial functional properties(foaming properties,amino acid composition)and structural characteristics including SDS-PAGE,circular dichroism,and endogenous fluorescence of RP hydrolysate(RPH)with different degree of hydrolysis(DH)were determined.Results showed that the protein recovery rate of RP under neutral conditions was significantly improved by keratinase(P<0.05).The foamability of RPH showed a trend of increasing first and then decreasing with the increase of DH.And there was no significant change in foaming stability among RPH.The contents of sweet amino acid,umami amino acid in RPH were significantly higher(P<0.05)compared with RP without hydrolysis.The result of SDS-PAGE showed that RPH was mainly composed of polypeptides with a molecular weight of less than 20 kDa.There was significant increase in the proportion of random coils and significant decrease in the proportion ofα-helix andβ-fold in the secondary structure of RPH than those in RP without hydrolysis(P<0.05),indicating that the secondary structure in RPH got more flexible and looser than that in RP without hydrolysis.The endogenous fluorescence results indicated that more contents of hydrophobic amino acids exposed in water phase after hydrolysis.This study would provide a theoretical basis for the development and utilization of RP products.