研究了不同pH 值下大豆分离蛋白的Zeta 电位、超速离心电泳、溶解性、荧光光谱及二级结构的变化及其规律，并进一步探讨了酸性条件下大豆分离蛋白亚基解离的机理．结果表明: 酸性条件下大豆分离蛋白的亚基解离主要是由分子间静电斥力导致的，而且大豆球蛋白的解离程度远大于β-大豆伴球蛋白; 溶液pH 值在2. 0~ 3. 0 之间时，Zeta电位达到最大值; 大豆分离蛋白在pH 值为2. 0，3. 0 时发生解离，在pH 值为3. 0 时解离程度达到最大，且与中性条件下的情况相比，其平均粒径提高了1. 1 倍，二级结构中无规则卷曲含量提高了15. 7%，荧光光谱最大吸收波长增大了4. 3 nm，pH 值的进一步降低会导致解离程度的下降; 而在pH 值为1. 0，7. 0 时大豆分离蛋白未发生解离; 未解离的大豆分离蛋白的溶解性随离心转速的提高大幅下降．

This paper deals with the effect of the pH value on the Zeta potentials,ultracentrifugation combined with electrophoresis,solubilities,fluorescence spectra and secondary structures of soybean protein isolates,with the mechanism of the subunit dissociation of the soybean protein isolates in acid conditions being also analyzed. The results show that the subunit dissociation is mainly due to the intermolecular electrostatic repulsion,and the extent of the dissociation of glycinin is much greater than that of β-conglycinin,that the Zeta potential reaches the maximum at a pH value between 2. 0 and 3. 0,and that the subunits dissociate when the pH value is 2. 0 and 3. 0. Moreover,it is found that,at pH 3. 0,the extent of the dissociation reaches the maximum,the average diameter of the soybean protein isolates is 2. 1 times that at pH 7. 0,the random coil content of the secondary structure increases by 15. 7%,and the maximum absorption wavelength in the fluorescence spectra increases by 4. 3 nm,and that,the extent of the dissociation decreases when the pH value is lower than 3. 0,the subunits do not dissociate when the pH value is 1. 0 and 7. 0,and the solubility of the undissociated protein decreases dramatically with the increase of the rotating speed of the ultracentrifugation.