牦牛枸杞酸奶发酵工艺优化及冻融处理次数对其品质的影响  

Optimization of fermentation process of yak wolfberry yoghurt and the effect of freeze-thaw treatment times on its quality

作　　者：范宇迪 罗毅皓[1] 孙万成[1] FAN Yudi;LUO Yihao;SUN Wancheng(College of Agriculture and Animal Husbandry,Qinghai University,Xining 810016,China)

机构地区：[1]青海大学农牧学院,青海西宁810016

出　　处：《中国酿造》2025年第2期164-170,共7页China Brewing

基　　金：青海省科技厅项目(2024-0301-ZJ)。

摘　　要：牦牛乳在加工过程中存在反复冻融现象,会降低酸奶品质。该研究以冻存的牦牛乳、红枸杞为原料制备牦牛枸杞酸奶,通过单因素及正交试验优化发酵工艺,并探索冻融循环2、4、6、8、10次对牦牛乳粒度、乳蛋白二级结构和酸奶理化指标的影响。结果表明,牦牛枸杞酸奶最优发酵工艺为红枸杞浆7%,白砂糖8%,发酵剂0.3%,发酵温度41℃,发酵时间9 h。在此优化条件下,酸奶感官评分为(85.14±1.86)分,表观黏度为(5.14±0.17)Pa·s,乳酸菌数为(5.13±0.32)×10^(9)CFU/g。随着冻融处理次数的增加牦牛乳粒度降低,二级结构发生改变,酸奶的弹性模量和粘性模量降低,内部三维空间结构坍塌,乳酸菌数减少,且在牦牛乳冻融6次之后酸奶持水力和酸度降低。因此,在实际生产过程中,牦牛乳冻融次数应控制为不超过6次。The yak milk has frozen and thawed repeatedly during processing,which will reduce the quality of yoghurt.Yak wolfberry yoghurt was prepared using frozen yak milk and red wolfberry as raw materials.The fermentation process was optimized through single-factor and orthogonal experiments,and the effects of freeze-thaw cycles of 2,4,6,8,and 10 on the particle size of yak milk,the secondary structure of milk proteins,and the physicochemical indexes of yoghurt were explored.The results showed that the optimal fermentation process conditions of yak wolfberry yoghurt were as follows:red wolfberry pulp 7%,sugar 8%,starter 0.3%,fermentation temperature 41℃,and fermentation time 9 h.Under the optimal conditions,the sensory score of yogurt was(85.14±1.86)points,the apparent viscosity was(5.14±0.17)Pa·s,and the lactic acid bacteria count was(5.13±0.32)×10^(9)CFU/g.With the increase of freeze-thaw treatment times,yak milk particle size decreased,secondary structure changed,elastic modulus and viscous modulus of yoghurt decreased,internal three-dimensional space structure collapsed,the lactic acid bacteria count decreased,and the water holding capacity and acidity of yoghurt decreased after 6 freeze-thaw times.Therefore,in the actual production process,the freeze-thaw treatment times of yak milk should be controlled not more than 6 times.

关 键 词：牦牛枸杞酸奶 发酵工艺优化 冻融处理次数 流变特性 微观结构 

分 类 号：TS252.42[轻工技术与工程—农产品加工及贮藏工程]