Microbial Growth, Survival, and Cryotolerance in Plant-Based Milk Alternatives: A Study with Listeria monocytogenes

The increasing popularity of plant-based milk products as an alternative to traditional bovine milk has sparked concerns about their safety and nutritional impact. This study focuses on the growth, survival, and cryotolerance behavior of Listeria monocytogenes (strains: ATCC 19115 and RS1) in various plant-based milk substitutes. Samples of almond milk, oat milk, soy milk, and bovine milk, all subjected to ultra-high temperature treatment, were evaluated for their influence on L. monocytogenes growth at 4°C and survival through repeated freezing and thawing cycles. Despite the nutritional differences, the growth rates of two L. monocytogenes strains at 4°C in plant-based milk alternatives and bovine milk displayed similarity (p > 0.05). Both strains of L. monocytogenes demonstrated similar biofilm formation abilities in plant-based milk alternatives and bovine milk. However, L. monocytogenes exhibited different levels of tolerance to repeated freezing and thawing cycles depending on plant-based milk alternatives in which they were grown at 4°C (p < 0.05). In the case of L. monocytogenes ATCC19115, cells cultured in almond milk at 4°C showed a significant reduction in their freezing and thawing tolerance (2.80 log reduction), followed by cells grown in soy milk (2.09 log reduction) when compared with oat and bovine milk (p < 0.05). A parallel trend of tolerance was evident in L. monocytogenes RS1 (2.82 and 3.22 log reduction in almond milk and soy milk, respectively). These findings underscore the need for comprehensive assessments of microbial behavior in emerging food products like plant-based milk alternatives. As these alternatives continue to gain traction, ensuring their safety and stability remains important. With insights into L. monocytogenes growth and survival in milk alternatives, this study will contribute to the evolving understanding of microbial dynamics in response to changing dietary trends.