氧化魔芋葡甘露聚糖的添加量对乳清分离蛋白凝胶性能的影响

Effect of the concentration of oxidized konjac glucomannan on gel properties of whey protein isolate gel

为改善乳清分离蛋白凝胶性能并提高其营养特性,将氧化魔芋葡甘露聚糖(oxidized konjac glucomannan,OKGM)与乳清分离蛋白(whey protein isolate,WPI)混合制备复合凝胶,研究OKGM添加量(1%、1.5%、2%、2.5%、3%)对WPI凝胶的持水性、质构、流变特性、热稳定性的影响,并对复合凝胶的形成机理进行了初步探讨。结果表明,OKGM的添加使复合凝胶的持水性(65.59%~93.42%)显著高于纯蛋白凝胶(53.58%);质构分析发现OKGM添加量为2%时凝胶的硬度、胶着性、咀嚼性达到最大值;流变分析发现复合凝胶是弱凝胶,对高频率和高温具有更高的依赖性;热重分析表明OKGM添加量≤1.5%时,OKGM-WPI复合凝胶的热稳定性均高于纯乳清分离蛋白凝胶;表面疏水性和游离巯基分析发现OKGM的添加降低了表面疏水性和游离巯基含量,说明OKGM与WPI发生交联和聚集形成复合凝胶;扫描电镜观察发现复合凝胶结构更为致密、有序。综上,可以通过添加OKGM改善WPI凝胶性能及稳定性。

Composite gels were prepared by mixing oxidized konjac glucomannan(OKGM)with whey protein isolate(WPI)to improve the properties of WPI gel and enhance its nutritional properties.The influence of OKGM addition amounts(1%,1.5%,2%,2.5%and 3%)on the water holding capacity,texture,rheological properties,thermal stability and microstructure of WPI gel was investigated.The mechanism of composite gel formation was studied as well.The water holding capacity of the composite gels(65.59%-93.42%)was significantly higher than that of pure WPI gel(53.58%)in the presence of OKGM.The texture revealed that the highest hardness,springiness,gumminess and chewiness of composite gels were observed at 2%OKGM addition amount.The OKGM-WPI composite gels were weak gels and had lower dependence on high frequency and high temperature.The thermal stability of OKGM-WPI composite gels was higher than that of pure WPI gel when the addition amount of OKGM was not more than 1.5%through thermogravimetric analyzer analysis.Surface hydrophobicity and free sulfhydryl group analysis suggested that the incorporation of OKGM reduced the surface hydrophobicity and free sulfhydryl content.This was due to the formation of composite gels between WPI and OKGM through cross-linking and aggregation.Scanning electron microscopy revealed that the composite gels had a denser structure and the pores were more ordered.In general,the addition of OKGM could improve the properties and stability of WPI gel.