热处理和转谷氨酰胺酶对凝固型酸乳品质的影响

Effects of Heat Treatment and Transglutaminase on the Quality of Set Yoghurt

为了揭示热处理和转谷氨酰胺酶(Transglutaminase,TGase)共同作用对凝固型酸乳品质的影响,本研究以不同条件热处理(70℃15 min、80℃15 min、90℃15 min、95℃5 min)的牛乳为原料,在发酵的同时添加不同浓度(0、5、10 U)TG酶,制得凝固型酸乳,并对其总体颜色变化值(ΔE)、持水性、硬度、pH和感官评分进行测定。结果表明,热处理温度由70℃升高到95℃会使酸乳(0 U,TGase)的ΔE升高18.86%,持水率升高12.39%,硬度升高7.48%,储存24 h和21 d时的pH分别降低0.19和0.13,并获得更浓郁的乳香。TG酶处理可以改善酸乳的稠度、口感、组织结构等感官特性,明显提高酸乳的持水率,降低色差和减缓后酸化速率,其作用效果随着TG酶浓度的升高而增大。在95℃下热处理5 min,添加10 U TG酶的酸乳拥有更好的品质特性,其色差较相同温度未加入TG酶的酸乳降低8.11%,持水率升高5.56%,储存24 h和21 d时的pH分别降低0.08和0.38,硬度也提升了23.30%。研究表明热处理和TG酶对提高酸乳的品质并改善酸乳的凝胶结构起协同作用,95℃热处理5 min,加入10 U TG酶可能是生产凝固型酸乳的最佳条件。

In order to reveal the effect of heat treatment and transglutaminase(TGase)treated on the quality of set yoghurt,the set yoghurt milk was prepared with raw milk by different heat treatment(70℃for 15 min,80℃for 15 min,90℃for 15 min,95℃for 5 min),and different concentration TGase(0,5 and 10 U)along with fermentation.The total color variation value(ΔE),water holding capacity,hardness,pH and sensory characteristics of set yoghurt were measured.The results showed that theΔE of set yoghurt(0 U TGase)increased by 18.86%with heat treatment temperature increasing from 70℃to 95℃,and its water holding rate increased by 12.39%,hardness increased by 7.48%,and the pH decreased by 0.19 and 0.13 after storage for 24 h and 21 d,and finally the set yoghurt got a richer mastic.TGase treatment could improve the sensory characteristics(consistency,mouth feel,tissue structure)of set yoghurt,increase the water holding capacity,reduceΔE and slow post-acidification rate.While its effect was positively correlated with the concentration of TGase.The set yoghurt heated at 95℃for 5 min and added 10 U of TGase had better quality characteristics than other samples.ItsΔE was 8.11%lower than the set yoghurt at the same temperature without added TGase,its water holding rate increased by 5.56%,its pH decreased by 0.08 and 0.38 after storage for 24 h and 21 d,and its hardness had also been greatly improved by 23.30%.The above results had shown that heat treatment and TGase could synergistically improve the quality and gel structure of yoghurt.Heated at 95℃for 5 min with 10 U TGase addition could be the best way to produce set yoghurt.