Biological Control of Listeria monocytogenes Growth in Fermented Buttermilk Enriched with Microfiltration Retentate

The use of protective cultures and probiotic lactic acid bacteria is considered a potential strategy for controlling Listeria monocytogenes in food systems, particularly in minimally processed and fermented products. However, the behavior of foodborne pathogens in complex dairy matrices, especially those enriched with byproducts of milk processing, remains insufficiently characterized. The aim of this study was to evaluate the survival of Listeria monocytogenes in buttermilk enriched with retentate obtained after microfiltration, in the presence of the probiotic strain Lactobacillus acidophilus LA-5^®. The study was conducted under different storage temperatures to reflect realistic conditions of product distribution and storage. The results demonstrated that fermented buttermilk with added retentate did not support the growth of Listeria monocytogenes under the tested conditions, and a gradual reduction in pathogen counts was observed during storage. The presence of Lactobacillus acidophilus LA-5^® was associated with a faster decrease in pathogen levels compared to samples without the probiotic strain. At the same time, lactic acid bacteria maintained high viability throughout the storage period. In contrast, predictive modelling using ComBase indicated the potential for pathogen growth under similar physicochemical conditions. This discrepancy highlights the limitations of predictive models when applied to complex, biologically active food matrices. These findings indicate that fermented buttermilk enriched with retentate may provide conditions limiting the survival of L. monocytogenes. However, the mechanisms responsible for the observed inhibition were not directly investigated in this study and require further research. The results emphasize the importance of experimental validation of predictive microbiology models and contribute to a better understanding of pathogen behavior in fermented dairy systems.