极端酸碱pH偏移改善白果蛋白溶解性和乳化性

Extreme acid and alkaline pH-shifting processes improving the solubility and emulsifying properties of Ginkgo seed protein isolate

以白果种子为原料提取蛋白,研究其分离蛋白经历极端酸性(pH 2.0、3.0、4.0)和极端碱性(pH 10.0、11.0、12.0)偏移处理2h后、再将pH恢复至中性后的溶解性和乳化性。基于0.5mol/LNaCl溶液体系,采用物理化学分析、光谱技术及电泳技术等手段表征白果分离蛋白的水化性质、分子组分和结构修饰以及蛋白分子聚集行为和乳化特性,探讨以上极端酸碱pH偏移对蛋白结构和功能性的影响。结果表明,极端酸碱偏移处理致使蛋白疏水性、巯基含量和内源性荧光强度均提高,促进蛋白分子展开、重排和疏水基团的暴露,形成由二硫键调节的分子聚集;显著提高蛋白溶解度(特别是pH10.0处理,溶解度从未处理组的13.42%增加到31.91%)和最高约为未处理组2倍的蛋白乳化活性,但降低蛋白乳化稳定性。

The solubility and emulsification properties of Ginkgo seed protein isolate(GSPI) were investigated after extreme acid(pH 2.0, 3.0, 4.0) and extreme alkaline(pH 10.0, 11.0, 12.0) treatment for 2 h and then the pH being returned to neutral. The hydration properties, molecular components and structural modifications of GSPI, as well as the aggregation behavior and emulsifying properties of the protein molecules based on aqueous solution system(containing 0.5 mol/L NaCl) were characterized by physical and chemical analysis, spectroscopy and electrophoresis techniques. The effect of extreme acid and alkaline pH-shifting processes on protein structure and functionality were discussed. The results indicated that extreme acid and alkaline p H-shifting processes increased the hydrophobicity, sulfydryl contents and endogenous fluorescence intensity of protein, promoted protein molecular unfolding, rearrangement and exposure of the hydrophobic groups, and formed molecular aggregation regulated by disulfide bonds. This markedly improved the solubility of protein. Especially, compared with the untreated group, p H 10.0 treatment made the solubility up to 31.91% from 13.42% and increased approximately 2-fold protein emulsion activity of the untreated group but decreased the protein emulsion stability.