Insights into the flavor formation mechanism of reduced-salt shallow-fermented sausages under oscillatory temperature fermentation with starter culture inoculation.

Inoculated fermentation is a promising strategy for enhancing the quality of sausage products. However, the underlying mechanisms by which it improves quality in traditional Sichuan air-dried sausages remain to be fully elucidated, which poses challenges for quality control during their production. The aim of this study is to reveal the dynamic evolution of flavor profiles and the metabolic networks of reduced-salt shallow-fermented sausages, prepared by employing Staphylococcus SM-75 as inoculating starter cultures and coupling it with oscillatory temperature fermentation process. Specifically, the key flavor compounds in the sausage samples are primarily composed of esters, aldehydes, and alcohols. Among these, ethyl caprylate, ethyl caprate, ethyl palmitate, ethyl caproate, 3-methyl-1-butanol, phenylacetaldehyde, and phenethyl alcohol are likely to make significant contributions to the distinctive flavor profiles. Untargeted metabolomics revealed that amino acid metabolism and lipid metabolism may be the primary metabolic pathways for their unique flavor formation during the two-step oscillatory-temperature fermentation. Moreover, the hot-air fermentation stage might be involved in enhancing amino acid metabolism. This can promote the degradation of proteins into free amino acids, and then converted into flavor precursors through transamination and decarboxylation reactions, such as phenethyl alcohol. The cold-air fermentation process is beneficial for the conversion of fatty acids into flavor compounds via the enzyme-mediated fatty acid degradation pathway, leading the generation of flavor substances or flavor precursors such as ethyl palmitate. Further, their key metabolic networks for the flavor formation of reduced-salt shallow-fermented sausages have been reconstructed. This study may provide a theoretical basis and practical guidance for enhancing the quality of reduced-salt shallow-fermented sausages during fermentation.