Isolation and screening of high-quality lactic acid bacteria and yeast strains in kefir grains and preparation of kefir compound fermentation starter

In this study, a total of ten strains of kefir grains were isolated. Lactic acid bacteria and yeast were the research subjects. The final compound fermentation starter was produced using Leu. Mesenteroides, Lactobacillus kefir, Lactobacillus casei, and K. marxianus. The fermented milk of the compound fermentation starter and kefir grains were compared in curding time, acidity, water holding capacity (WHC), ethanol content, the viability of strains, and sensory score. The results showed that the quality of the fermented milk was similar, but the kinds of volatile aroma components in the kefir produced by the compound strain starter were significantly more than those of the kefir grains. The result of this study will help simplify and stabilize the industrial production of kefir, and provide a reference for the development of different flavored yogurt products. Novelty impact statement The dominant kefir grain strains were divided to create the strain compound starter, which can be used in place of kefir grains. It can ferment and produce a milk drink with similar characteristics to traditional kefir grains. The dairy industry can develop using strain starters to overcome the limitations of kefir grains and produce kefir products with consistently high quality.