Regulating the Quality, Fatty Acid Metabolism, and Volatile Flavor Substance Formation of Fermented Sausages with a Compound Fermentation Agent of Lactic Acid Bacteria and Staphylococcus xylose

To optimize the quality and flavor of fermented sausages, this study used a fermentation starter prepared by blending Lactobacillus rhamnosus 6001, Lactobacillus plantarum 21790, Pediococcus pentosaceus 22228, and Staphylococcus xylosus 21445 in equal proportions to create a fermentation starter culture for fermented sausage production. Using natural fermentation as a control, the study investigated the regulatory effects of this starter culture on the physicochemical properties, free fatty acid metabolism, and the formation of volatile flavor compounds in the sausages. The results indicated that the blended starter culture significantly reduced the pH and water activity of the sausages, enhancing storage stability and food safety. It also improved product color and texture, with brightness (L*), the a*/b* ratio (redness/yellowness), and total color difference (ΔE) all significantly superior to those of the control group. Texture parameters such as hardness and elasticity were also markedly improved. Regarding fat metabolism, a total of 14 free fatty acids were detected. In the compound group, the levels of key components such as palmitic acid and oleic acid, as well as the total content, were significantly higher than those in the control group at all fermentation stages, effectively promoting fat hydrolysis. A total of 61 volatile flavor compounds were detected using HS-SPME-GC-MS. First, OPLS-DA was used to screen for 10 key flavor markers common to both groups, including n-hexanal, 1-octen-3-ol, methyl hexanoate, and nonanal; Subsequently, the odor activity values (OAVs) were used to quantify their contribution to the final aroma. The OAVs of characteristic aroma compounds such as n-hexanal, 1-octen-3-ol, and linalool in the blended group were significantly higher than those in the control group. Among these, the OAV of n-hexanal reached 690.22, making a prominent contribution to the grassy and oily aromas. Taken together, these findings indicate that the blended starter culture significantly enhances the accumulation of low-threshold, high-contribution aroma compounds—such as esters, aldehydes, and ketones—through synergistic metabolism, endowing the product with rich and harmonious flavor layers including fruity, buttery, and grassy notes. By regulating fatty acid metabolism and the production of flavor compounds, this blended starter culture significantly improved the overall quality of fermented sausages, providing a theoretical basis and technical support for new product development and industrial production.