The variation patterns of microorganisms in sheep milk under different heat treatments and storage times

The microbial stability of sheep milk is closely linked to its heat treatment process. This study investigated the dynamic effects of different heating temperatures on the microbial community structure and functional potential during storage. Raw sheep milk and milk treated at 65, 75, 85, and 95°C were stored, and the microbial communities were analyzed using 16S rRNA gene sequencing and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2) functional prediction. The results showed that alpha diversity peaked on day 6 and then gradually decreased, with the 95°C treatment maintaining the highest diversity by the end of storage. Beta diversity analysis revealed significant spatiotemporal differentiation in community structure. Initially, all samples consisted mainly of the phylum Proteobacteria and the genus Stenotrophomonas . Over time, the abundance of Bacteroidota and Firmicutes increased, with different temperature treatments selecting distinct terminal dominant bacterial genera, such as Staphylococcus aureus in the 95°C group and Moraxella osloensis in the 65°C group. Functional prediction revealed that microbial metabolic strategies shifted from carbohydrate utilization in the early storage period to stress response and maintenance in the later period. This study provides a theoretical basis for optimizing the heat treatment process of sheep milk to extend its shelf life and ensure food safety. • Microbial stability of sheep milk is closely linked to its heat treatment process. • Raw sheep milk and milk were treated at different temperatures an analyzed. • Bacteroidetes and Firmicutes abundance progressively increased during storage. • Storage time and heat temperature jointly influence microbial community succession. • Storage time is the key factor influencing the microbial community of sheep milk.