不同比例酪蛋白与牛明胶酶促交联产物的功能性质

Somefunctional properties of the composites enzymatic crosslinked from casein and bovine gelatin mixed in different ratios

将酪蛋白和明胶以2∶1、4∶1和6∶1的质量比混合,并利用转谷氨酰胺酶进行酶促反应,制备酪蛋白-明胶交联复合物,通过对交联复合物功能性质的测定,研究明胶比例不同对复合物功能性质的影响,以发新型蛋白质配料。在5%(w/v)底物浓度下,每克蛋白质添加转谷氨酰胺酶10 U,45℃反应4 h,等电点沉淀除去游离明胶和交联明胶,得到4-羟脯氨酸含量分别为51.37、33.38、25.97 g/kg蛋白质的3个复合物。复合物在pH 4.5或更低时溶解性优于酪蛋白,但在中性或弱碱性时则低于酪蛋白。与酪蛋白相比,复合物的吸水性、吸油性均有显著提高,明胶含量高的复合物其吸油性较高,而吸水性相应较低。不过,复合物的体外消化能力低于酪蛋白,并且随着明胶含量的增加其体外消化能力降低。

Casein and bovine gelatin were mixed in three ratios of 2：1,4：1,6：1（ w /w）,respectively,and treated by transglutaminase to prepare three casein-gelatin composites,which were then evaluated for their functional properties to reveal whether the addition levels of bovine gelatin had impacts on the evaluated properties and if the composites were potential as new protein ingredients for food processing.Under the selected reaction conditions such as transglutaminase addition of 10 U/g protein,reaction temperature of 45℃ and reaction time of 4 h,together with an isoelectric precipitation procedure for the prepared composites to remove the free and cross-linked gelatin,three composites thus obtained had 4-hydroxyproline content of 51.27,33.38,25.97 g/kg protein,respectively.The composites had better solubility than casein at pH 4.5 or lower pH,but showed lower solubility than casein at neutral or alkaline conditions.Compared to casein,the composites had better water holding capacity and oil absorption capacity.The composite containing more gelatin also exhibited higher water holding capacity but lower oil absorption capacity.The composites showed lower in-vitro digestibility compared with casein,especially if more gelatin was crosslinked into the composite.