Abstract:The survival rate and low temperature stability of lactic acid bacterial starter obtained by vacuum freeze-drying are governed by several factors. In this paper, the influence of the technology of high cell density cultivation and vacuum freeze-drying on cryotolerance of lactic acid bacteria for use as starters was analyzed. During fermentation, the following factors had a significant effect on the cryosurvival of lactic acid bacteria: culture medium, temperature control, pH stat, the neutralizer used, the harvesting stage of the cell crop, and post-fermentation handling of the concentrated cells. Factors affecting cell viability subjected to lyophilization include the following: cryoprotectants used, conditions used in initial freezing of the cell concentrate, and during vacuum freeze-drying. A good understanding of these factors will provide a reliable technology for preserving high cell density starter. The use of starter bacteria with high cryotolerance and viability can improve the quality of fermented milk products and boost economic benefits to the dairy industry.
