与液态酸奶相比，冻干酸奶块更加方便食用，大豆基冻干酸奶块的研发将为植物基酸奶增添新的品种。作者考察了预冻温度、混料温度对大豆基冻干酸奶块产品质构特性和乳酸菌存活率的影响，对比了牛乳基冻干酸奶块与大豆基冻干酸奶块的性质。研究表明，大豆酸奶冻干料液的共晶温度以及玻璃化转变温度分别为-9.04 ℃和-30.73 ℃，与牛乳酸奶料液差别不大。发现预冻温度越高，产品的质构越疏松易碎，乳酸菌存活率越低。另一方面，预冻温度过低也会使乳酸菌存活率降低，同时由于水汽升华通道过于狭窄容易引起产品结构塌陷，最终确定适宜的预冻温度为-25 ℃。提高混料温度能够小幅提升冻干酸奶块提乳酸菌存活率，但对产品质构无明显影响。研究发现，虽然牛乳基酸奶块的乳酸菌存活率更高，但在贮藏30 d的产品中，大豆基冻干酸奶块中的乳杆菌及双歧杆菌的存活情况与牛乳基酸奶块接近。在不充氮包装情况下，大豆基冻干酸奶块中乳杆菌及双歧杆菌的存活率更高。
Compared to liquid yogurt, freeze-dried yogurt blocks offer greater convenience for consumption. The development of freeze-dried soy-based yogurt blocks introduces new product varieties to plant-based yogurt. This study investigated the effects of pre-freezing temperature and mixing temperature on the textural characteristics and viability of lactic acid bacteria in soy-based freeze-dried yogurt blocks, while the properties of freeze-dried dairy-based yogurt blocks were compared with those of freeze-dried soy-based yogurt blocks. The results revealed that the eutectic temperature and glass transition temperature of soy-based yogurt freeze-dried mixture were -9.04 ℃ and -30.73 ℃, respectively, which were comparable to those of dairy-based yogurt mixtures. It was found that higher pre-freezing temperatures resulted in looser and more fragile product texture along with lower viability of lactic acid bacteria. Conversely, excessively low temperatures of pre-freezingreduced bacterial viability and led to structural collapse due to the narrow water vapor sublimation channels. Ultimately, a pre-freezing temperature of -25 ℃ was determined to be suitable. Increasing the mixing temperature could slightly increase the viability of lactic acid bacteria in freeze-dried yogurt blocks without significantly affecting the product texture. Although dairy-based yogurt blocks exhibited higher bacterial viability, freeze-dried soy-based yogurt blocks showed comparable viability of Lactobacillus and Bifidobacterium after 30 days of storage. The viability of Lactobacillus and Bifidobacterium in freeze-dried soy-based yogurt blocks was higher without nitrogen-filled packaging.
HU Boxiao, LI Xingfei, ZHANG Zhao, CAO Lianfeng, WANG Caili, HUA Yufei. Study on Process Conditions and Product Characteristics of Freeze-Dried Soy-Based Yogurt Blocks[J]. Journal of Food Science and Biotechnology,2023,42(10):41-50.