Screening of the freeze-drying protective agent for high-quality milk beer yeast (Kluyveromyces marxianus) and optimization of freeze-drying process conditions

摘要

Milk beer is a new type of milk beverage produced by two-stepfermentation of lacticacid bacteria and yeast and created first in China. Yeast is the key strain of milk beerfermentation, which determines the flavor and quality of milk beer. In this study,the preparation process of high-qualityyeast strain MJ1 active freeze-driedpowdersuitable for milk beer fermentation was optimized. Results showed that the optimalfreeze-driedprotective agent was used: sucrose 11.27%, mannitol 4.88%, maltodextrin15.43%, skimmed milk powder 7.82%, and applying the optimal freeze-dryingconditions: rotation speed 6,000 rpm, centrifugation time 15 min, the mixing ratio ofcentrifugal bacterial sludge and the protective agent is 1:1.5, the mixing equilibriumtime is 30 min, the cell survival rate of strain MJ1 can reach 90.21% ± 1.04%. It laidthe foundation for the preparation of active freeze-driedyeast powder and the industrialproduction of milk beer.