以大豆蛋白微粒构建高蛋白食品体系的稳定性研究

本研究以大豆分离蛋白（SPI）为原料，在pH 3.0、pH 3.4和pH 3.8等低酸性pH条件下对其进剪切热处理，制备获得粒度分布在2~100 μm的大豆蛋白微粒。当微粒制备的pH条件向SPI等电点（pH 4.5）靠近时，形成蛋白微粒的结构越致密，稳定性越高。在pH 3.8条件下制得微粒的内部蛋白含量达到34.22%，在pH 2.0~8.0范围内其粒径不发生明显改变，蛋白溶出率不超过13%。经过二次热处理（95 ℃、30 min），该微粒的粒径和形貌没有发生明显变化，其分散液的粘度明显低于SPI分散液，在12%的浓度下仍然不形成凝胶。微粒化过程可以封闭大豆蛋白的疏水基团和氢键结合位点，使蛋白分子间的相互作用减弱，导致粘度降低。该大豆蛋白微粒可应用于饮料、酸奶等高蛋白食品体系中，在保持其口感的同时增加其蛋白质含量。
Soy protein isolate (SPI) was subjected to shear and heat treatment under acidic conditions (pH 3.0, 3.4 and 3.8), and protein particles distributed from 2 to 100 μm were obtained. As prepared at pH condition was more close to the isoelectric point of SPI, the resulting particles had a higher degree of microparticulation and a better stability. For the soy protein particles prepared at pH 3.8, their internal protein content was 34.22%, and their protein leakage did not exceed 13% within the range of pH 2.0 to 8.0. The change of pH and re-heat treatment (95 ℃ for 30 min) had little effects on their particle size and morphology. Compared to SPI dispersion, the viscosity of soy protein particle dispersion decreased significantly after heat treatment. And heat-set gelation did not occur in this dispersion even when the particle concentration was 12%. These protein particles could be used in the high-protein foods such as beverage and yogurt, so as to make them have smooth mouthfeel and fortify their protein content.