γ-氨基丁酸/L-瓜氨酸增强白果分离蛋白凝胶性

γ-Aminobutyric acid/L-citrulline enhancing the gelation of Ginkgo biloba seed protein isolate

摘要:

以白果分离蛋白（GSPI）为成胶基质材料，制成溶液向其中分别加入γ-氨基丁酸（GABA）和L-瓜氨酸（L-Cit）,均质后再将溶液pH分别调至5.0，6.0和7.0，制备热诱导凝胶。采用物化分析法、机械力学、蛋白凝胶电泳，SEM及FTIR表征GSPI/氨基酸溶胶的物性、凝胶性和微观结构，并探讨他们对GSPI凝胶性能的影响及其机理。结果表明，以上两种氨基酸对GSPI溶解度无提升作用，但能显著降低蛋白疏水性；GABA促进溶胶聚集并降低其ζ-电位，而L-Cit在pH 7.0时则促进解聚和提高ζ-电位；两者均能促进蛋白分子疏水基团向内折叠。在pH 5.0和pH 7.0时，以上两种氨基酸特别是L-Cit显著提高蛋白凝胶性能，而在pH 6.0时则弱化凝胶性能。其影响机制可能是氨基酸与GSPI之间的静电作用，而这种效应依赖于所在体系的pH。

Abstract:

As a gel forming material, ginkgo seed protein isolate (GSPI) was used. Following the addition of γ-aminobutyric acid (GABA) and L-citrulline (L-Cit) to the GSPI solutions and homogenization, the pH of sols was adjusted to pH 5.0, 6.0, and 7.0, respectively. Heat-induced gels were prepared from these pre-treated samples. Physiochemical properties, mechanical mechanics, protein electrophoresis, SEM, and FTIR were used to determine the physiochemical characteristics, gelation, and microstructure of the mixture of GSPI/GABA and GSPI/L-Cit. A hypothesis was proposed to investigate how GABA, L-Cit, and pH influence gelation and potential mechanisms. The results have shown that GABA/L-Cit have no influential effects on protein solubility, but they have the ability to reduce their hydrophobicity; GABA promoted protein aggregation and lowered their ζ-potentials, whereas L-Cit assisted protein dissociation but also increased ζ-potential of the sols at pH 7.0. Moreover, the two amino acids facilitated the folding of hydrophobic groups inside the protein molecule. Additionally, the two amino acids, especially L-Cit, significantly enhanced protein gelation, but significantly decreased it when pH was 6.0. Variations in these changes can be attributed to a pH-dependent manner.