Screening of a High-Quality Milk Beer Yeast Strain and Comparative Study of the Effects of Liquid Strain and Freeze-Dried Strain on Milk Beer Quality

a high-quality milk beer yeast strain was screened and identified from wild kefir grains. The effect of this new strain on milk beer production in the form of fresh liquid and freeze-dried strains as starter was studied by comparing it with the control. The physical and chemical properties, water holding capacity, rheology, texture, sensory evaluation, and volatile compound composition of milk beer was used as specific evaluation indicators, and the effects of two different forms of starter on the product quality of milk beer were analyzed. Results indicated that using lyophilized starter cultures resulted in milk beer with higher pH and lower ethanol content. Different types of starters had no significant effect on WHC, rheological, and textural properties of milk beer. The application of freeze-dried starter resulted in better performance of milk beer samples in terms of smell and overall evaluation, and more stable product quality between production batches of milk beer samples. Aroma components were the key indicators for the flavor evaluation of milk beer. Although some acid and ester volatile compounds formed by the milk beer samples produced from freeze-dried starter were less than those of milk beer samples fermented by liquid starter, the type of overall volatile aroma components and content was not significantly different. In terms of fermentation stability, the freeze-dried strain starter had stable performance and was more suitable for producing standardized milk beer products. Therefore, these results provide a scientific basis for large-scale use of active freeze-dried yeast strains to produce milk beer products.