本研究以大豆分离蛋白（SPI）作为乳化剂和稳定剂，吸附在油水界面，形成O/W（水包油）型乳液（蛋白浓度2.0 wt%，大豆油浓度20.0 wt%），在人工胃液的模型中（37℃，pH 1.2，34 mM NaCl离子强度，95 r/min持续摇动2 h），检测乳液的粒径，Zeta电位和显微结构。通过检测乳液的显微结构和粒径表明，大豆分离蛋白（pH 7.0）能够形成稳定的乳液，但在人工胃液的模型中，乳液液滴会出现絮凝或结合现象。并且，液滴絮凝或结合程度取决于水解时间。乳液的Zeta电位检测结果表明，SPI乳液与人工胃液混合后，乳液的Zeta电位由﹣35.9±0.3 mV变化到﹢16.3±0.9 mV。对未经乳化的SPI溶液和乳化后的乳液进行SDS-PAGE分析表明，吸附到油水界面的SPI蛋白更容易被胃蛋白酶水解。本研究能够提高人们对O/W型SPI乳液基于人工胃液模型下降解特性的认识，对设计以SPI乳液为基础的食品系统具有重要的指导意义。

Soybean protein isolate (SPI) adsorbed on the oil-water interface was used as an emulsifier and stabilizer to form an oil-in-water (O/W) emulsion (2.0 wt% protein and 20.0 wt% soybean oil). The characteristics of SPI-stabilized emulsions, including changes in particle size, zeta potential, and microstructure, under the action of simulated gastric fluid (37 ℃, pH 1.2, and 34 mM NaCl ionic strength, with continuous shaking at approximately 95 r/min for 2 h) were investigated. The microstructure and diameter of the emulsion showed that SPI (pH 7.0) was capable of forming a stable emulsion, but underwent extensive droplet flocculation or coalescence when mixed with simulated gastric fluid. The degree of droplet flocculation or coalescence markedly depended upon hydrolysis time. The zeta-potential values gradually changed from -35.9±0.3 mV to +16.3±0.9 mV after the emulsion was mixed with simulated gastric fluid. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that when SPI was present at the interface of the O/W emulsion, it was more easily hydrolyzed by pepsin as compared to native SPI solution. This study improves our understanding of the characteristics of an O/W emulsion stabilized by SPI in simulated gastric fluid and has high significance for guiding the design of food systems based on SPI emulsions.

国家自然科学基金资助项目（31371782）；河南省教育厅科学技术研究重点项目基础研究计划（14A550007）；河南工业大学校基金基础研究重点培育计划（2013JCYJ04）