【作者】 张婷； 李晓； 段飞霞；

【Author】 Zhang Ting;Li Xiao;Duan Feixia;College of Textile and Food Science,Sichuan University;Key Laboratory of Food Science and Technology in Sichuan Province,Sichuan University;

【机构】 四川大学轻纺与食品学院； 四川大学食品科学与技术四川省高校重点实验室；

【摘要】 本论文以冻干酸奶的水分活度、活菌数、色泽、疏松度等作为主要评价指标,采用单因素实验结合正交实验的方法,对采用程序真空冷冻干燥技术制备常温保存的活菌性固体酸奶的工艺参数进行了优化,减少干燥过程中酸乳营养成分和风味的损失,旨在解决活菌性酸乳冷链储运能耗大、携带不便、保质期短等问题。采用混合菌种(嗜热链球菌:保加利亚杆菌为4:1)发酵酸奶,成品酸奶中乳酸菌含量约4.8×10~8 cfu/g。实验结果表明:程序冻干各工艺参数对活菌性常温固体酸奶品质影响大小依次为:第一阶段冷冻时间>第一阶段冷冻温度>第二阶段冷冻时间>第二阶段冷冻温度>第四阶段冷冻时间/温度>第三阶段冷冻时间/温度=预冻时间/温度。正交实验得到酸奶的最佳冷冻干燥条件为:-45℃/2h(预冻)—-30℃/12h—0℃/3h—10℃/5h—35℃/5h,在冻干过程中控制环境真空度为1Pa。在此条件下,酸奶冻干得率为25%,干燥后的酸奶产品水分活度Aw为0.47,乳酸菌活菌数量达2.0×10~7 cfu/g～1.0×10~8 cfu/g,感官品质良好,贮藏稳定性较好(37℃恒温,15d)。更多还原

【Abstract】 In this work,the vacuum freeze-drying technology was applicated in developing an room-temperature-stored and active-probiotic-contained Yogurt,to decrease of Energy consumption during storage and cold chain transport,as well as to prevent the loss of nutritional and flavor ingredients during drying.The vacuum freeze-drying technics parameters for active-Lactobacillus-contained solid yoghurt were optimized by the single factor experiment and orthogonal experiment.The Aw,the viable count of Lactobacillus strains and the sensory quality were determined and analyzed.The Thermophilus:Bulgaricus(4-1) were used for yoghurt fermentation,and the vitality of the Lactobacillus strains of the liquid yoghurt reached to 4.8× 10~8 cfu/g.The results showed that the time and temperature of freeze drying at each stage will affect the status of the product(time of stage 1 > temperature of stage 1 > time of stage 2 > temperature of stage 2 > time/temperature of stage 4 > time/temperature of stage 3 = time/temperature of pre-freeze stage).The result of orthogonal experiments suggested that the optimum freeze-drying conditions for yoghurt were as follows:-45 ℃/2 h(pre-frozen);-30 ℃/12 h;0 ℃/3 h;10 ℃/5 h;5℃/5 h,and the vacuum degree of control environment was 1 Pa.In the condition,with good sensory quality and storage characteristics(37 ℃,15 d),the moisture activity Aw of products were assayed to be 0.47,and the vitality of the Lactobacillus strains were maintained ranging from 2.0 × 10 to 1.0 × 10~8 cfu/g,the products yield was 25%.Thus,it is effective to ensure the survival of active probiotics during the drying process of yoghurt,and to ensure the nutritional and health-care performance of yoghurt products.更多还原