超声处理结合pH值调控对白果分离蛋白/乳清分离蛋白复合凝胶特性的影响

Effect of Ultrasound Combined with pH Adjustment on Gelling Properties of Ginkgo Seed Protein Isolate/Whey Protein Isolate Composite Gels

为研究超声处理结合pH值调控对白果分离蛋白与乳清分离蛋白复合凝胶性能的影响,本实验对复合蛋白溶液的物化性质、蛋白分子行为及所形成热诱导凝胶的质构、持水性及微观结构进行表征。结果表明:超声功率为总功率的25%、45%和65%时对蛋白溶解度均无显著影响,超声结合较低的pH值(pH 4.0)处理能够显著降低蛋白疏水性、提高蛋白表面巯基含量并增大溶胶粒径。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳及傅里叶变换红外光谱分析结果证明超声处理影响了蛋白分子的结构和聚集行为。经热诱导后,在较低pH值条件下复合蛋白形成的凝胶质地性能较差,而在较高的pH值条件下(特别是在pH 5.0时)复合蛋白所形成凝胶的质地性能较好,持水性较高。复合蛋白凝胶的质地性能和持水性均随着超声功率的增加而明显提升,其归因于超声处理强化了白果分离蛋白与乳清分离蛋白中羟基基团的相互作用,促进了蛋白分子的聚集和交联,并改善了复合蛋白凝胶结构的紧密性。综上所述,超声处理结合pH值调控可有效改善复合蛋白凝胶的功能特性。

To investigate the effects of ultrasound treatment combined with pH adjustment on the gelling properties of composite gels prepared from ginkgo seed protein isolate(GSPI)and whey protein isolate(WPI),the physicochemical properties and molecular behavior of the GSPI and WPI mixture and the texture,water-holding capacity(WHC)and microstructure of the heat-induced gel of the protein mixture were characterized.Results showed that ultrasonic treatment at 25%,45%,or 65%power alone did not significantly influence protein solubility.However,ultrasonic treatment combined with lower pH(pH 4.0)markedly decreased protein hydrophobicity,and increased surface sulfhydryl group content and the sol’s particle size.The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)and Fourier transform infrared(FTIR)spectroscopy showed that ultrasonic treatment affected protein structure and aggregation behavior.The heat-induced composite gel formed at lower pH had poor textural properties,whereas the composite gel formed at higher pH(especially at pH 5.0)exhibited improved textural properties and higher WHC.The textural properties and WHC of the composite protein gel were significantly improved with increasing ultrasonic power,which was attributed to the fact that ultrasonic treatment strengthened the interaction between hydroxyl groups in GSPI and WPI,promoting protein aggregation and cross-linking and improving the structural compactness of the composite gel. Overall, ultrasound treatment combined with pH adjustment could be an effective method for improving the functional properties of the composite protein gel.