热处理和转谷氨酰胺酶对凝固型酸乳品质的影响

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。

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

Abstract: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 the ΔE 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,reduce ΔE 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. Its ΔE 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.