谷氨酰胺转氨酶添加量对酸羊乳凝胶特性的影响

摘要

In this research,yogurt was fermented using the goat milk treated with different concentrations of transglutaminase (TG;1,2,3 u/g protein) at 40 ℃ for 2 h to investigate the effects of TG concentration on yogurt coagulation time,and the acidity,water holding capacity,texture characteristics and microstructure at the end of fermentation and 24 hours after fermentation.The results showed that the coagulation time of the goat milk treated by TG gradually decreased with the increase of TG concentration,but the acidity in curd and fermentation of 24 h had no significant change (p ＞ 0.05) when added different concentrations of TG.The water holding capacity of goat yogurt could be improved significantly(p ＜ 0.05) with TG treatment,especially when the concentration of TG was 2 to 3 u/g protein.The texture analysis showed that hardness and viscosity at the end of fermentation and post-fermentation of 24 h of goat yogurt increased significantly with the increase of TG concentration(p ＞0.05).TG processing had no significant effect on cohesiveness of goat milk at the end of fermentation (p ＞ 0.05),while it had significant influence on cohesiveness after fermentation of 24 h (p ＜ 0.05).However,TG treatment had little effect on goat yogurt elasticity (p ＞ 0.05).By observing the microstructure of acid goat milk,it was found that the protein in goat's milk treated with TG concentration of 2-3 u/g protein was easier to form denser network structure,which facilitated the formation of goat yogurt gels.Overall,the gel properties of goat milk could be improved with the TG treatment in concentration of 2-3 u/g protein.%采用不同添加量(1、2、3 u/g蛋白)谷氨酰胺转氨酶(transglutaminase,TG)在40℃下处理羊乳2h后制备酸羊乳,研究TG添加量对酸羊乳凝乳时间,凝乳时及后发酵24 h时的酸度、持水性、质构特性和微观结构的影响.结果表明,TG处理羊乳后制备的酸羊乳其凝乳时间随着TG浓度的增大逐渐缩短,但TG浓度对酸羊乳凝乳时和后发酵24 h的酸度无明显影响(p ＞0.05);TG处理可显著提高酸羊乳的持水性(p＜0.05),尤其是TG浓度为2 ～3 u/g蛋白时效果更加明显;质构分析表明,随着TG浓度的增大,酸羊乳凝乳时和后发酵24 h的硬度和黏性显著增加.TG处理酸羊乳凝乳时的内聚性无明显影响(p＞0.05),但对后发酵24 h时的内聚性影响显著(p＜0.05).然而TG处理对酸羊乳弹性影响不大(p＞0.05);通过对酸羊乳的微观结构观察发现,用TG添加量为2 ～3 u/g蛋白处理羊乳制备的酸羊乳中蛋白质形成更加致密的网络结构,有利于酸乳凝胶的形成.