Pathogen survival in dairy and plant-based probiotic fermented beverages containing Lacticaseibacillus rhamnosus GG

The survival of Lacticaseibacillus rhamnosus GG and two foodborne pathogens (Staphylococcus aureus and Escherichia coli) was monitored in L. rhamnosus GG – supplemented dairy milk and three plant-based alternatives (soy, almond, and coconut). Microbiological measurements were taken during fermentation (24 hours) and refrigerated storage (21 days, 4°C), using the L. rhamnosus GG – supplemented dairy group as the reference matrix for comparisons. Across all matrices, L. rhamnosus GG maintained counts above 7 log CFU·mL–1 throughout the experimental period. L. rhamnosus GG numbers did not differ significantly between dairy and plant-based milks (P>0.05). Although time, milk type, and their interaction were statistically significant (P<0.05), the observed shifts did not translate into a loss of L. rhamnosus GG culturability, and counts remained stable across milk types during storage. By day 21, S. aureus and E. coli counts were lower in almond and coconut milk than in soy and dairy milk (P<0.05). Overall, plant-based milk alternatives particularly almond and coconut appeared to be effective carriers for L. rhamnosus GG and performed comparably to dairy milk in sustaining probiotic viability. Because pathogen reduction was matrix-dependent, future work should examine underlying matrix-microbe interactions and validate these findings at industrial scale using integrated microbiological, physicochemical, and compositional analyses.