谷氨酰胺内肽酶限制性水解对大豆伴球蛋白乳化性的影响

Effect of Glutamyl Endoproteinase Modification on Emulsifying Properties of β-conglycinin

摘要:

天然的7S球蛋白于pH=7.5通过谷氨酰胺内肽酶(E.C. 3.4.21.19)的特异性酶切，结合超滤的方法（截留分子量为10 kDa），制得7S-核心区（7S-core）。该方法能去除7S球蛋白的α、α’亚基延展区，且不影响α、α’亚基的核心区及β亚基。本研究采用β-伴大豆球蛋白（7S）、7S酶解产物（7S-GE）及7S-核心区（7S-core）作为乳化剂，制备了三种乳液。研究了这三种乳液在改变pH、离子强度和储藏对乳液稳定性的影响，表征了乳液的zeta-电位，平均粒径和乳析指数，采用光学显微镜观察了乳液的微观结构。实验结果表明，7S经酶切后，形成的乳液的表面电位的绝对值减小。7S-core乳液的电位的绝对值明显小于7S及7S-GE乳液；同时，粒度及界面蛋白量显著增加。且失去延展区的7S制备的乳液在不同的pH、离子强度条件下聚集程度增加，放置后乳液的乳析指数增大，且显微结果表明乳液液滴发生聚合，乳化稳定性明显下降。本研究表明，延展区对于天然7S球蛋白的乳化能力和乳化稳定性具有重要的意义。

Abstract:

A soy β-conglycinin (7S) hydrolysate (7S-GE), obtained by the hydrolysis by the glutamyl endoproteinase (E.C. 3.4.21.19) at pH 7.5. The core region of 7S (7S-core) was prepared by filtered the 7S-GE through the micro-filter member with 10 kDa molecule cut-off. The emulsifying ability of 7S, 7S-GE and 7S-core were investigated using zeta-potential, droplet size and saturation surface load. The results showed that the emulsion formed by 7S-core had lower zeta-potential and significant higher droplet size and saturation surface load compared with the emulsion which formed by 7S and 7S-GE. The influence of pH, iron strength on the stability of the emulsions formed by 7S, 7S-GE and 7S-core were investigated. The results showed that the stability of the emulsion formed by 7S-core was decreased remarkably against the pH, iron strength. Higher creaming index and coalescence of oil droplet through the microscope were observed. This study demonstrated emulsifying ability and stability of 7S remarkably depended on the extension regions.