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

天然的7S球蛋白于p H=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 k Da),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p H、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p H、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。

A soy β-conglycinin(7S) hydrolysate(7S-GE), obtained by the hydrolysis by the glutamyl endoproteinase(E.C. 3.4.21.19) at p H 7.5. The core region of 7S(7S-core) was prepared by filtered the 7S-GE through the micro-filter member with 10 k Da 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 p H, 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 p H, 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.