State Key Laboratory of Food Science and Technology and School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, China.
J Agric Food Chem. 2010 Jul 14;58(13):8035-42. doi: 10.1021/jf101045b.
Soy protein isolate (SPI), beta-conglycinin (7S), and glycinin (11S) were subjected to pH-shifting treatments, that is, unfolding at pH 1.5 or 12.0 followed by refolding at pH 7.0, to induce molten globule structures. Treated samples were analyzed for protein solubility, thermal stability, and aggregation in 0, 0.1, and 0.6 M NaCl solutions at pH 2.0-8.0. The pH(12) shifting resulted in drastic increases (up to 2.5-fold) in SPI solubility in the pH 6.0-7.0 range, especially at 0 M NaCl. The pH(1.5) shifting had a generally lesser effect on solubility. 11S exhibited a solubility pattern similar to that of SPI, but the solubility of 7S was unaffected by pH shifting except at 0.6 M NaCl. The pH shifting, notably at pH 12.0, produced soluble, disulfide-linked polymers from 11S and reduced (P < 0.05) its enthalpy but not its temperature of denaturation. Soy proteins structurally altered by pH shifting had a reduced sensitivity to thermal aggregation.
大豆分离蛋白（SPI）、β-伴球蛋白（7S）和大豆球蛋白（11S）经过 pH 值转换处理，即在 pH 值 1.5 或 12.0 下展开，然后在 pH 值 7.0 下复性，以诱导形成无定形球蛋白结构。在 pH 值 2.0-8.0 下，在 0、0.1 和 0.6 M NaCl 溶液中分析处理样品的蛋白质溶解度、热稳定性和聚集情况。pH 值为 12.0 的转换导致 SPI 在 pH 值 6.0-7.0 范围内的溶解度大幅增加（高达 2.5 倍），尤其是在 0 M NaCl 时。pH 值为 1.5 的转换对溶解度的影响一般较小。11S 表现出与 SPI 相似的溶解度模式，但除了在 0.6 M NaCl 时，7S 的溶解度不受 pH 值转换的影响。pH 值转换，特别是在 pH 值 12.0 时，可从 11S 产生可溶的、二硫键连接的聚合物，并降低（P<0.05）其焓值，但不改变其变性温度。通过 pH 值转换改变结构的大豆蛋白对热聚集的敏感性降低。
