Hot-water fish protein (HFP) , enzymatic fish protein (EFP) , acid soluble fish protein (AFP) and alkaline soluble fish protein (ALFP) were prepared by heating extraction, enzyme hydrolysis, acid/alkaline solubili-zation-isoelectric precipitation from Tilapia head.Nutritional characteristics, solubility and emulsifying properties of these proteins were determined.The protein content of ALFP and AFP was found to be 89.97% and 85.87% , respectively.Total essential amino acids were about 49.72% and 48.63% of the total amino, respectively.The content of crude fat and ash and degree of whiteness of these proteins are significantly lower than that of HFP or EFP (P < 0.05).In the pH range 2.0 to 10.0, EFP and HFP were found to have a high solubility of > 93% , at the same time, a low emulsifying activity and less stability were observed.In contrast, solubility of AFP and ALFP is very sensitive to pH.In pH range 4.0 to 6.0, their solubility and emulsifying properties were poor, but these properties are greatly improved when pH is in the range of 4.0 to 6.0.The emulsifying activity index and emulsifying stability index of AFP and ALFP were significantly higher than that of HFP and EFP.These results indicated that fish protein having better nutritional characteristics and emulsifying properties could be prepared by acid/alkaline solubilization-isoelectric precipitation.%以罗非鱼头为原料,采用加热浸提、酶法水解、酸/碱溶解-等电点沉淀法提取鱼蛋白,冷冻干燥得到4种鱼蛋白粉,分别记为热提鱼蛋白(HFP)、酶解鱼蛋白(EFP)、酸溶鱼蛋白(AFP)和碱溶鱼蛋白(ALFP),并探讨了4种鱼蛋白的营养特性、溶解性和乳化性.结果表明:ALFP和AFP的蛋白含量分别为89.97％和85.87％,必需氨基酸占总氨基酸的比例达到49.72％和48.63％,而脂肪和灰分含量以及白度值均低于HFP和EFP,且差异显著(P＜0.05).溶解性和乳化性的研究显示,EFP和HFP在pH 2.0 ～10.0内溶解度均高于93％,但体系的乳化活性和稳定性较差；而AFP和ALFP的溶解度随pH值的变化非常明显,在pH 4.0 ～6.0内,体系的溶解性和乳化性极差,而在pH值低于4.0或高于6.0时,溶解度大大增强,乳化活性和乳化稳定性随之提高,且乳化活性和稳定性明显高于HFP和EFP.酸/碱溶解-等电点沉淀法可用于制备营养价值高,乳化特性相对较好的鱼分离蛋白.
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