College of Light Industry and Food Engineering,Nanjing Forestry University
将CaCl2加入质量浓度分别为120 g/L银杏果分离蛋白及5.0 g/L果胶(两种酯化度,分别为38%和76%)的复合溶液中,使钙离子最终质量浓度分别0.05 g/L、0.11 g/L和0.22 g/L,基于此复合溶液制备热诱导复合凝胶。采用粒径和ζ-电位法、流变学及质构学、蛋白凝胶电泳技术、红外光谱和扫描电镜技术表征成胶分子物化性质、成胶性过程及复合凝胶功能性和微观结构,以探讨Ca2+对蛋白/果胶复合物胶凝性影响及其潜在的机制。结果表明,Ca2+降低成胶复合物大小但不改变复合物的带电量；降低热诱导凝胶流变学特性,形成结构松散的复合凝胶；进而弱化凝胶质构特性但对其持水性无显著影响。Ca2+破坏蛋白与果胶间的作用,竞争性地与果胶结合。随着Ca2+浓度增加,以上效应越为显著。相比之下,高酯化度果胶比低酯化度果胶对Ca2+更为敏感。
Calcium chloride with final mass concentration of 0.05 g/L, 0.11 g/L and 0.22 g/L were added to mass concentration of 120 g/L ginkgo seed protein isolate (GSPI) and 5.0 g/L pectin (with two types of degree of esterification, which was 38% and 76%, respectively) composite solutions. The above prepared solutions were then heated to develop a GSPI/pectin composite gel. The determination of particle size and ζ-potential, rheology, texture profile analysis, protein electrophoresis, spectroscopic and microscopic techniques were employed to detect physiochemical characteristics of gel-forming solutions, gelling and functional properties of the resulting composite gels and their microstructure. The mode of action caused by calcium chloride was also prospected. The results indicated that calcium ions reduced the particle size of GSPI/pectin but not affected their electric charge, degraded rheological properties of the heat induced gels, formed a composite gel with a loosen structure. Accordingly, the textural propertied of the gels was weakened, whereas the water holding capacity was not significantly deteriorated. It was supposed that calcium ions impair the interaction between GSPI and pectin due to competitive binding to pectin and hence disrupt the balance of GSPI/pectin assembly. As the calcium concentration increased, the effects were notably prominent. The pectin with higher degree of esterification was more sensitive to calcium ions.