Insights into the mechanism of nutty aroma formation by 𝘚𝘵𝘢𝘱𝘩𝘺𝘭𝘰𝘤𝘰𝘤𝘤𝘶𝘴 𝘴𝘢𝘱𝘳𝘰𝘱𝘩𝘺𝘵𝘪𝘤𝘶𝘴 in fermented sausages

To achieve a starter culture with the ability of improving nutty aroma in the formulation of fermented sausage, this study evaluated sixteen staphylococci strains first, then demonstrated the function of the strain in sausage fermentation using volatolomics and metagenomics. Within sixteen tested strains, S. saprophyticus 108 presented superior safety and technological properties and produced the highest amounts of 3-methylbutanal. With spontaneously fermented sausage as control, S108 group distinctly enhanced the production of 3-methylbutanal, 3-methylbutanoic acid and its ethyl ester, and nutty note of S108 group was obviously perceivable. The relative abundance of S. saprophyticus in both control and S108 groups increased throughout the fermentation process and such increase was more dramatic in S108 group. Although the differences in the number of functional genes predicted by control and S108 group in CAZy, eggNOG, and KEGG databases were comparatively small, the contribution of S. saprophyticus to major nutrient metabolisms was the main difference. Both S. saprophyticus and L. mesenteroides were annotated with predominant abundances in main metabolic pathways, while S. saprophyticus abundance involved in the metabolic pathways was higher in S108 group than in control. Specifically, branched-chain amino acid degradation, phenylalanine metabolism, glycolysis, pyruvate metabolism, butanoate and propanoate metabolism, glycerolipid and glycerophospholipid metabolism were mainly driven by S. saprophyticus, linked to the higher generation of volatile compounds in S108 group compared to control. The results provided scientific support for developing a functional starter culture through clarifying the mechanism of nutty aroma formation by S. saprophyticus in the production of fermented sausages.