TG酶和漆酶对双歧杆菌益生菌酸奶品质的影响

为了比较谷氨酰胺转氨酶(TG酶)和漆酶的添加对双歧杆菌益生菌酸奶感官、蛋白质交联及组织质构变化的影响,测定和分析了两种酶交联益生菌酸奶的游离氨基变化率、感官、质构、表观黏度、蛋白条带及微观结构,并添加阿魏酸改善漆酶酸奶的品质。结果表明:当TG酶用量增加时,TG酶交联酸奶的游离氨基变化率、感官得分和硬度显著增大(p<0.05),胶黏性、粘聚性及表观黏度先增大后减小(p<0.05),内聚性变化不显著(p>0.05),TG酶最佳用量为1.8 U/g;随着漆酶用量的增加,漆酶酸奶游离氨基变化率、感官得分、硬度、内聚性、胶黏性、粘聚性及表观黏度均先增大后减小(p<0.05),漆酶最佳用量为0.3 U/g;添加4.5 mmol/L的阿魏酸明显改善了漆酶交联酸奶的感官、质构及表观黏度;所有待测酸奶中均缺少β-lg条带,TG酶交联酸奶的κ-CN和β-CN条带消失,聚集成了新的蛋白质,而漆酶交联酸奶和阿魏酸+漆酶酸奶与对照及TG酶酸奶相比,分子量在14 kDa的蛋白条带明显变宽;经两种酶交联的酸奶,三维网络结构变得致密,TG酶交联酸奶的胶粒分布更均匀,网络结构更致密,且在漆酶交联酸奶中添加了阿魏酸后,相较于漆酶交联酸奶,蛋白胶束聚集的更紧密,从而得出,不同类型酶对牛奶乳蛋白质交联的催化作用不同,但均可改善酸奶的感官及食用品质。

Effect of TGase and laccase on the quality of probiotics yogurt

In order to contrast the effect of adding TGase or laccase on the sensory quality,protein cross-linking and texture change of bifidobacteria-yoghurt. The rate of change of free amino groups,sensory scores,texture charateristics,apparent viscosity,protein bands and microstructure of the enzymatic cross-linking probiotic yogurt were measured and analyzed,and adding ferulic acid to improve the quality of lactase yogurt. The results showed that the rate of change of free amino groups,the sensory scores and hardness value of yoghurt treated with TGase were significantly increased(p<0.05). Gumminess,cohesiveness and apparent viscosity were increased and then decreased(p<0.05),and no significant difference(p>0.05)for adhesiveness was found with increasing addition of TGase. The optimal addition of TGase was 1.8 U/g. With elevating addition of laccase,increasing and then decreasing trends for the rate of change of free amino groups,sensory scores,hardness,adhesiveness,gumminess,cohesiveness and apparent viscosity were observed(p<0.05). The optimal addition of laccase was 0.3 U/g.The sensory and qualitative properties for laccase cross-linked yogurt were significantly improved(p<0.05)by adding 4.5 mmol/L ferulic acid. There was a shortage of β-lg in all yogurt. Protein bands of κ-CN and β-CN of yoghurt treated with TGase disappeared,and new proteins formed,while compared with the control and yogurt treated with TGase,protein bands of yogurt treated with laccase or with ferulic acid and laccase were significantly widened about 14 kDa of molecular weight. The three-dimensional network structure of yogurt by enzyme crosslinking became denser than control. Yogurt treated with TGase had more uniform distribution of particles and more compact network structure than laccase cross-linking yogurt. And the addition of ferulic acid was able to make protein micelles of laccase cross-linking yogurt more tightly packed together. Therefore,different types of enzymes had different catalysis on milk protein cross-linking,but all improved the sensory and edible quality of yogurt.