Investigation of Kokumi Substances and Bacteria in Thai Fermented Freshwater Fish (Pla-ra)

Abstract

A 16S rRNA next-generation sequencing technique was applied to investigate the microbial diversity and liquid chromatography–tandem mass spectrometry was used to identify glutamyl peptide profiles of 10 Thai fermented freshwater fish (Pla-ra) samples. A total of 12 genera of bacteria were able to be detected, with Tetragenococcus spp., Staphylococcus spp., and Lactobacillus spp. dominating. Of the 18 glutamyl peptides analyzed, 17 were found, even though the amounts detected were lower than the taste threshold. Despite this, an increase in mouthfulness sensation, reflecting kokumi activity, was clearly identified in most of the samples, which might be because of a synergistic effect of different sub-threshold compounds present in the samples. In principle component analysis, the relationship between microorganisms and glutamyl peptide generation was observed, especially between Tetragenococcus spp. and Lentibacillus spp. and the generation of γ-Glu-Val-Gly. Correlations between microbial diversity and the generation of taste enhancers were identified in this study.

Enzymatic Synthesis of γ-Glutamylvalylglycine Using Bacterial γ-Glutamyltranspeptidase

“…The kokumi intensity of γ-Glu-Val-Gly is 12.8 times higher than that of GSH. Moreover, the addition of 0.01% γ-Glu-Val-Gly significantly increased the intensity of sweetness, saltiness, and umami of the food. , In nature, γ-Glu-Val-Gly is present in several foods such as scallops, fermented fish sauces, shrimp pastes, soy sauce, miso, and fermented fish …”

“…6,7 In nature, γ-Glu-Val-Gly is present in several foods 8 such as scallops, 9 fermented fish sauces, 10 shrimp pastes, 11 soy sauce, 12 miso, 13 and fermented fish. 14 We previously reported a method to produce kokumi seasoning by γ-glutamylation of gluten hydrolysate using Bacillus amyloliquefaciens γ-glutamyltranspeptidase (GGT; EC 2.3.2.2). 15 GGT catalyzes the hydrolysis of γ-glutamyl compounds and the transfer of their γ-glutamyl moieties to other amino acids and peptides.…”

Factors affecting bacterial community dynamics and volatile metabolite profiles of Thai traditional salt fermented fish

“…These microbial community are also similar to the microbial profile in another fermented fishery product such as Korean salted and fermented seafood called Jeotgal (5, 6), salt-fermented shrimp paste (1) and anchovy sauce Budo (7). Even though the comparable trends of bacterial profiles were proposed, many environmental factors including raw materials, formulation, equipment and production process were highly affected microbial community dynamics during fermentation (2).…”

“…These bacteria have an important role in flavour characteristic of product attributed to their lipolytic and proteolytic activities (24, 27). A positive relationship between the presence of Virgibacillus and Tetragenococcus and the generation of glutamyl peptides responsible for taste enhancers of Pla-ra has been acknowledged (1). It was also reported that an increase of Staphylococcus was accompanied by the development of esters in relation with their high catalytic activity (4, 28).…”

“…After fermentation Pla-ra contains both fine meat texture and thickening meat-derived liquid providing Kokumi taste (1) with fishy and volatile metabolite aroma. Pla-ra manufacturing is significantly different from fish sauce.…”