Effects of salinity and fermentation time on the microbial community, flavor, and metabolites of shrimp paste

This study utilized Antarctic krill meat and shrimp heads as raw materials, which were fermented for 56 days at 22-28 °C with salt concentrations of 20% and 25%. Samples were taken and examined every seven days during the fermentation process. This method not only leverages shrimp heads-a byproduct-to impart unique flavor to shrimp paste but also embodies sustainable food processing principles. The study examined physicochemical indicators, microbial community structure, volatile flavor compounds, and differential metabolite content changes in fermented shrimp paste under varying salt concentrations. High-throughput sequencing (16S rDNA) revealed Firmicutes and Proteobacteria to be the dominant bacterial phyla, with Lentibacillus, Psychrobacter, and Carnobacterium emerging as the dominant genera. Using the gas chromatography-Ion Mobility Spectrometry (GC-IMS) for qualitative analysis of volatile flavor compounds in shrimp paste, 59 volatile flavor compounds and 14 key flavor compounds were identified. Analysis by headspace gas chromatography-mass spectrometry (HS-GC-MS) revealed that amino acids are the key differential metabolites in shrimp paste, serving as the primary compounds responsible for its umami flavor. Correlation analysis further revealed that at 25% salt concentration, the microbial community significantly increases the formation of volatile compounds, while at 20% salt concentration, the different metabolites contribute more prominently. At both salt concentrations, Lentibacillus showed a positive correlation with the abundance of multiple metabolites, and adenosine 5'-monophosphate also showed synergistic effects with various microorganisms. This study not only provides a basis for the selection of salt concentrations for the development of shrimp paste, but also provides a reference for the development of other sustainable aquatic product processing technologies.