苦荞蛋白质的低消化性研究Ⅱ——酶解产物的超微结构分析和分子量分布

Study on Microstructure and Molecular Weight Distribution and Digestibility in vitro of Tartary Buckwheat Protein Hydrolysates

苦荞麦蛋白质氨基酸组成平衡,生物价高,并且具有独特的生理功能。体外消化实验表明其蛋白质的消化率较低,通过扫描电镜对四种蛋白质组分酶解产物的超微结构进行观察发现,胃蛋白酶作用于四种组分的方式是不同的,胃蛋白酶不仅可以作用与清蛋白和球蛋白的表面,而且随着水解进程的延长胃蛋白酶还可以作用与清蛋白和球蛋白的内部结构,因此其体外消化率相对较高。而对于醇溶蛋白和谷蛋白,其高级结构相对较为稳定,胃蛋白酶只能作用于其表面,很难作用其内部结构,所以这两种蛋白组分的体外消化率相对较低。此外还通过高效液相对其酶解物的分子量分布进行研究,结果表明,清蛋白和球蛋白的酶解产物分子量相对较低,组分多,酶解程度高。醇溶蛋白酶解物的组成较为简单,这可能是由于被胃蛋白酶作用的位点较少所造成的。而谷蛋白,其酶解物的分子量分布广,高分子量的组分所占比例大,这表明其被酶解的程度相对较低。

Tartary buckwheat protein consists of well-balanced amino acid with higher biological value, and it has some special physiological properties. In vitro pepsin digestibility assay showed that its digestibility was rather low. Scanning electron microscopy（SEM） was used to examine the microstructure of four protein fractions hydrolysates. The results showed that the four protein fractions were digested by pepsin with different patterns. Albumin and globulin are more digestible, since they are digested by being hydrolyzed from the outer surface to the inner part. Prolamin and glutelin were rather resistant to pepsin digestion because of their complex structure. High performance liquid chromatography was used to determine the molecular weight distribution of the four protein fractions hydrolysates. The results revealed that the hydrolysates of albumin and globulin are composed of low molecular weight fractions, and the zymolysis is better. But the hydrolysates molecular weights of prolamin are rather variable because of its sturcture.