Microbial-Dependent Variations in Umami Compounds during Fermentation of Prawn By-Products

Abstract

This study investigated the effects of microbial fermentation on the umami taste components of prawn by-products. Six microorganisms—Aspergillus oryzae, Rhizopus oligosporus, Saccharomyces cerevisiae, Bacillus subtilis, Lactiplantibacillus plantarum and Latilactobacillus sakei —were used to ferment prawn by-product juice. The resulting broths were analysed for umami-related compounds, including free amino acids and flavour nucleotides. Taste activity values (TAVs) and equivalent umami concentrations (EUCs) were calculated to assess umami intensity. Fermentation enhanced acidity and significantly increased the concentrations of umami-active compounds. The EUC values increased markedly from 0.23 g monosodium glutamate (MSG)/100 g at day 0 to 6.36 g MSG/100 g on day 3 in samples fermented by R. oligosporus. Glutamic acid was identified as the dominant umami taste compound and its TAV exceeded 1 in fermented samples, confirming a perceptible umami contribution. Among the tested strains, Rhizopus oligosporus produced the most pronounced umami profile, indicating its potential as an effective starter culture for transforming prawn by-products into value-added, umami-rich ingredients.