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 improve the solubility and emulsifying properties of ginkgo seed protein isolate

摘要:

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2 h后、再将pH恢复至中性后的溶解性和乳化性。基于0.5 mol/L NaCl溶液体系，采用物理化学分析、光谱技术及电泳技术等手段，通过测定白果蛋白溶液的物化性质以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pH 10.0处理，溶解度从13.42%增加到31.91%）和最高约为对照组2倍的蛋白乳化活性，但降低蛋白乳化稳定性。

Abstract:

Ginkgo seed was used as raw foodstuffs to exact their proteins. The resulting ginkgo seed protein isolate (GSPI) was then subjected to pH-shifting treatments followed extreme acid (pH 2.0, pH 3.0, pH 4.0) or extreme alkaline (pH 10.0, pH 11.0, pH 12.0) by holding 2 h and then the pH was recovered to neutral. The solubility and emulsifying properties of pH-shifted GSPI were investigated. Upon the aqueous solutions (containing 0.5 mol/L NaCl), the physical and chemical analysis, spectroscopy and electrophoresis techniques were employed to detect the physical and chemical properties of the ginkgo protein solution to characterize the hydration properties, molecular components and structural modifications of the ginkgo protein isolate, as well as the aggregation behavior and emulsifying properties of the protein molecules, and investigate the effect of extreme acid and alkaline pH-shifting on protein structure and functionality thereof. The result indicated that extreme acid and alkaline pH-shifting processes cause the rise of protein hydrophobicity, sulfhydryl group content and fluorescence intensity, promotes protein unfolding, rearrangement and disclose their hydrophobic groups to form a disulfide-mediated aggregation, led to markedly improved solubility (particularly, the solubility is up to 31.91% from 13.42% of the control) and approximately 2-fold emulsion activity but decreased emulsion stability.