Repeated Cycles of Freeze-Thaw Storage Influence the Dynamics of Bacterial Communities and the Prevalence of Pathogens in Mutton.

During the journey from the abattoir to the consumer, mutton is often exposed to temperature fluctuations. However, the effects of temperature variation on bacteria in mutton remain to be investigated. To address this gap, our study used high-throughput sequencing and quantitative PCR techniques to investigate the effects of repeated freezing (- 18 °C) and chilling (4 °C) on the bacterial community and quality of Hu sheep meat. Our findings revealed that the richness and evenness of the bacterial community in mutton were decreased with prolonged low-temperature treatment. Moreover, distinct dominant taxa were identified in freeze-chilled and frozen-stored mutton, with specific lineages, such as Pantoea agglomerans, exhibiting enrichment exclusively in the former. Additionally, freezing preservation markedly reduce the absolute abundance of bacteria, encompassing both pathogenic and spoilage bacteria, whereas freeze-chill cycles were shown to substantially increase the absolute abundance of bacteria including both pathogenic and spoilage bacteria. Notably, fluctuations in the relative abundance of bacterial taxa do not necessarily correspond to alterations in their absolute abundance.