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.