Changes in the Quality and Nontargeted Metabolites of Salt-Fermented Shrimp (Saeu-jeot) Based on Fermentation Time

Saeu-jeot is a widely consumed variety of jeotgal, a South Korean salt-fermented food. However, there is a lack of existing studies conducting nontargeted metabolomic analyses of saeu-jeot during fermentation. To evaluate the changes in saeu-jeot during fermentation, saeu-jeot samples were fermented for 360 days under controlled conditions. Samples collected at different time points were subjected to physicochemical (including nontargeted metabolomic analysis) and microbial analyses. As fermentation progressed, the pH decreased and acidity increased, whereas total nitrogen, amino-nitrogen, and specific amino acid concentrations increased. Nontargeted metabolite analysis supports these results. Metabolite profiling classified changes in saeu-jeot during fermentation into those occurring in the early (15-45 days), middle (60-180 days), and late (270-360 days) stages. Pathogenic bacteria were not detected, and biogenic amine levels were not elevated, suggesting that saeu-jeot is safe to consume. Overall, pH, amino-nitrogen, and pathogenic bacteria, according to the fermentation stage of saeu-jeot, can be useful parameters for evaluating the quality of salted shrimp.