Seasonal frost improves probiotic and nutrient availability in fermented vegetables

Climate-driven shifts in seasonal frost patterns raise important questions about their impact on food quality and resilience. Here, we show that a single 12-h frost event at harvest can enhance both the microbial and nutritional properties of fermented cabbage and carrots, two cold-tolerant crops widely grown in the U.S. Northeast. Using microbial amplicon and metagenomic sequencing, we found that frost exposure led to subtle but consistent changes in microbial composition, including greater abundance of cold-adapted taxa such as Leuconostoc and Debaryomyces. These changes corresponded to increased abundance of genes involved in vitamin biosynthesis, particularly menaquinone (K₂), cobalamin (B₁₂), and threonine pathways. Nutritional assays confirmed higher concentrations of vitamins A and E in frost-conditioned carrot ferments and increased vitamin K₁ in cabbage. Our findings suggest that exposure to seasonal frost can enhance the health-promoting and sensory qualities of fermented vegetables, offering a novel strategy for value-added, climate-resilient food production in temperate regions.