Characterization of Protein Hydrolysis and Odor-Active Compounds of Fish Sauce Inoculated with Virgibacillus sp. SK37 under Reduced Salt Content

The effect of Virgibacillus sp. SK37, together with reduced salt content, on fish sauce quality, particularly free amino acids and odor-active compounds, was investigated. Virgibacillus sp. SK37 was inoculated with an approximate viable count of 5 log CFU/mL in samples with varied amounts of solar salt, for example, 10, 15, and 20% of total weight. Eighteen selected odorants were quantitated by stable isotope dilution assays (SIDA), and their odor activity values (OAVs) were calculated. Samples prepared using 10% salt underwent spoilage after 7 days of fermentation. The viable count of Virgibacillus sp. SK37 was found over 3 months in the samples containing 15 and 20% salt. However, acceleration of protein hydrolysis was not pronounced in inoculated samples at both 15 and 20% salt. Virgibacillus sp. SK37, together with salt contents reduced to 15-20%, appeared to increase the content of 2-methylpropanal, 2-methylbutanal, 3-methylbutanal, acetic acid, and 2-methylpropanoic acid. However, only aldehydes were found to have an effect on the overall aroma of fish sauce based on high OAVs, suggesting that the inoculation of samples with Virgibacillus sp. SK37 under reduced salt contents of 15-20% likely contributed to stronger malty or dark chocolate notes.