Lacticaseibacillus rhamnosus H7 shapes flavor-associated microbial-metabolic networks in low-nitrite sausages: insights from a multi-omics correlation study

Lactic acid bacteria (LAB) are commonly used to degrade nitrite in dry fermented sausages. However, the impact of nitrite-degrading LAB on flavor formation and its regulatory effects on the microbial community, free amino acid (FAA), and lipid metabolism associated with flavor development are not yet fully understood. This study investigated the effects of Lacticaseibacillus rhamnosus H7-a nitrite-reducing strain-on the microbial community, flavor compounds, and metabolites using multi-omics and FAAs analysis. Results showed that the inoculation of Lcb. rhamnosus H7 became dominant, promoted the release of FAAs, and enhanced the accumulation and transformation of specific lipids (e.g., PE, TG, and PC). Correlation analysis revealed that Lcb. rhamnosus H7 was positively associated with the abundance of Weissella hellenica and Weissella minor. This might be further linked to enhanced amino acid and lipid metabolism, which coincided with the increased formation of key flavor compounds such as hexanoic acid and ethyl 2,4-hexadienoate. Overall, this study demonstrates that the inoculation of Lcb. rhamnosus H7 can modulate microbial structure and promote amino acid and lipid metabolism, improving the content of characteristic flavor compounds. This study also provides a reasonable hypothesis for the potential mechanism by which LAB regulate the flavor of low-nitrite dry fermented sausages.