为了研究超声波联合酶技术提高大豆分离蛋白（Soybean Protein Isolated，SPI）在酸性条件下（pH 4）乳化性能的效果，本文以大豆分离蛋白为原料，以乳化性能和乳状液粒径为衡量指标，确定超声波联合植酸酶-酸性蛋白酶（Ultrasound combined with phytase-acidic protease，Uphy-aci）改性方法的最适宜条件。研究发现，当SPI浓度6%，植酸酶添加量4 U/g，酸性蛋白酶添加量1500 U/g，植酸酶与酸性蛋白酶的酶解时间分别为50 min和30 min时，改性后的SPI（pH 4）乳化性能明显增加，乳状液粒度减小；通过表面疏水性（H0）和扫描电镜（SEM）分析了超声波-酶复合改性处理的SPI，发现在酸性条件下，SPI表面疏水性含量为487.78，比未改性提高了71.2%，并呈现破碎均一、多孔的微观结构。因此，超声波与植酸酶-酸性蛋白酶联合改性提高酸性条件下SPI的乳化特性等功能性质，并且拓宽了大豆分离蛋白的应用领域。

In order to study the effect of ultrasound-enzymatic modificationon the emulsifying properties of soybean protein isolate (SPI) under acidic conditions (pH 4), SPI was used as the raw material in this study. The emulsifying properties and particle sizes were used as evaluating indices to determine the optimum conditions for the modification method using ultrasound combined with phytase-acidic protease (Uphy-aci). The results showed that, when the SPI concentration was 6%, the amount of phytase was 4 U/g, that of the acid protease was 1500 U/g, and the durations of enzymatic hydrolyses using phytase and acidic protease were 50 min and 30 min, respectively. The emulsion performance was significantly increased and the size of the emulsion particles decreased. The surface hydrophobicity, H0, and the scanning electron microscope (SEM) were used to analyze the structure of SPI under the optimal Uphy-aci conditions. The surface hydrophobicity of SPI was 487.78 under acidic conditions and was enhanced by 71.2% compared to that of the unmodified sample. Moreover, SPI presented a homogeneous and porous microstructure. Therefore, the ultrasound-enzymatic modification method can effectively improve the emulsifying properties and functional properties of SPI in acidic conditions, and expand the applications of SPI.

国家科技支撑项目(大豆产业链共性关键技术创新与示范)（2014BAD22B01）