Changes in Lactic Acid Bacteria Counts in Fermented Milk and Fermented Milk Beverages During Refrigerated Storage Under Commercial Conditions

초록

In this study, changes in lactic acid bacteria (LAB) counts were evaluated in commercially produced fermented milk and fermented milk beverage products from the day of manufacture to the end of their shelf life under refrigerated storage conditions. LAB viability was monitored at multiple time points to assess stability in industrial production and distribution environments. All products were stored at 4℃ ± 1℃, reflecting standard commercial refrigeration conditions. The fermented milk and fermented milk beverage products exhibited high initial LAB counts after manufacture. Although gradual reductions in viable counts were observed during refrigerated storage, LAB levels remained consistently above the internal quality criteria throughout the designated shelf life. In products containing Bifidobacterium spp., counts obtained using selective enumeration media were generally lower and showed a greater decline during refrigerated storage than total LAB counts. These findings are consistent with those of previous studies, highlighting the importance of initial inoculation density and product-specific formulation in maintaining LAB viability during storage. Notably, this study provides field-based empirical data obtained from commercially manufactured products under real storage conditions, thereby extending the findings of laboratory-scale studies. Overall, these results emphasize the importance of adequate initial LAB inoculation, continuous monitoring of LAB viability, and application of product-specific quality management strategies. This study provides practical and scientific evidence to support the establishment of robust quality-control criteria and optimization of manufacturing processes for fermented dairy products.

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