The effects of ultrasound and acid on the aggregation, structures and emulsifying properties of soybean protein isolate (SPI) were investigated. Results of solubility showed that ultrasonic treatments at 0.001 M HCl increased the content of soluble SPI. The particle size of soluble aggregates subjected to ultrasonication and acid was initially decreased and then increased with increasing ultrasonic time. Secondary structure analysis, by circular dichroism, indicated lower a-helix and higher random coil amounts in SPI treated with short ultrasonic time, in contrast to the higher a-helix and lower random coil in SPI treated with longer time (more than 20 min). Emulsions prepared with SPI by 10 min of ultrasonication demonstrated significantly (P < 0.05) small droplet sizes and long term stability in comparison with their untreated counterparts. These results highlight that the emulsifying properties of SPI can be significantly improved by the synergistic effect of ultrasound and acid.

研究了超声波和酸对大豆分离蛋白（SPI）的聚集，结构和乳化特性的影响。溶解度结果表明，在0.001 M HCl下进行超声处理可增加可溶性SPI的含量。经过超声处理和酸的可溶性聚集体的粒径最初随着超声时间的增加而减小，然后增加。通过圆二色性的二级结构分析表明，用较短的超声时间处理的SPI中较低的a螺旋和较高的随机线圈数量，而用较长时间（大于20分钟）处理的SPI中较高的a螺旋和较低的随机线圈数量。经SPI超声10分钟制备的乳液表现出明显的（P <0.05）与未经处理的液滴相比，液滴尺寸小且具有长期稳定性。这些结果表明，超声和酸的协同作用可以显着改善SPI的乳化性能。