‡College of Food Science, Northeast Agricultural University, Harbin, Heilongjiang 150030, People's Republic of China.
§Synergetic Innovation Center of Food Safety and Nutrition, Harbin, Heilongjiang 150030, People's Republic of China.
J Agric Food Chem. 2015 May 20;63(19):4853-61. doi: 10.1021/acs.jafc.5b01331. Epub 2015 May 12.
Changes in the structural and gel textural properties were investigated in soy protein isolate (SPI) that was subjected to extreme acid pH-shifting and mild heating processes. The SPI was incubated up to 5 h in pH 1.5 solutions at room temperature or in a heated water bath (50 or 60 °C) to lead to protein structural unfolding, followed by refolding at pH 7.0 for 1 h. The combination of pH-shifting and heating treatments resulted in drastic increases in the SPI gel penetration force (p < 0.05). These treatments also significantly enforced the conversion of sulphydryl groups into disulfides, increased the particle size and hydrophobicity values, reduced the protein solubility (p < 0.05), and strengthened the disulfide-mediated aggregation of SPI. The intrinsic fluorescence spectroscopy results indicated structural unravelling when protein was subjected to acidic pH-shifting in combination with heating processes. The slight loss of secondary structure was observed by circular dichroism. These results suggested that pH-shifting combined with heating treatments provide great potential for the production of functionality-improved SPI, with the improved gelling property highly related to changes in the protein structure and hydrophobic aggregation.
研究了极端酸性 pH 值变化和温和加热过程对大豆分离蛋白 (SPI) 的结构和凝胶质构特性的影响。SPI 在室温下或在加热水浴（50 或 60°C）中在 pH 1.5 的溶液中孵育长达 5 小时，导致蛋白质结构展开，然后在 pH 7.0 下复性 1 小时。pH 值变化和加热处理的组合导致 SPI 凝胶渗透力急剧增加（p < 0.05）。这些处理还显著促进了巯基向二硫键的转化，增加了颗粒大小和疏水性值，降低了蛋白质溶解度（p < 0.05），并增强了 SPI 的二硫键介导的聚集。内源荧光光谱结果表明，当蛋白质在酸性 pH 值变化与加热过程相结合时，结构会解开。圆二色性观察到二级结构略有损失。这些结果表明，pH 值变化与加热处理相结合为生产功能改善的 SPI 提供了巨大潜力，改善的胶凝特性与蛋白质结构和疏水性聚集的变化密切相关。
