To understand the umami taste of fermented broad bean paste (FBBP) and explore the umami mechanism, eight peptides (PKALSAFK, NKHGSGK, SADETPR, EIKKAALDANEK, DALAHK, LDDGR, and GHENQR) were separated and identified via ultrafiltration, RP-HPLC, and UPLC-QTOF-MS/MS methods. Sensory experiments suggested that eight novel peptides showed umami/umami-enhancing and salt-enhancing functions. Significantly, the threshold of EIKKAALDANEK in aqueous solution exceeded that of most umami peptides reported in the past 5 years. The omission test further confirmed that umami peptides contributed to the umami taste of FBBP. Molecular docking results inferred that all peptides easily bind with Ser, Glu, His, and Asp residues in T1R3 through hydrogen bonds and electrostatic interactions. The aromatic interaction, hydrogen bond, hydrophilicity, and solvent-accessible surface (SAS) were the main interaction forces. This work may contribute to revealing the secret of the umami taste of FBBP and lay the groundwork for the efficient screening of umami peptides.

Pixian broad-bean paste (PBBP) is a famous fermented condiment in China, which may produce abundant flavor peptides during fermentation process. Herein, the tasteful peptides from fermented broad-bean (FB) were separated...

Broad bean fermentation is of vital importance in PixianDouban (PXDB) production, as well as a key process for microorganisms to degrade protein, which lays the foundation for the formation of PXDB flavor. In this study, two fungi and bacteria were screened, and their morphology, molecular biology, growth, and enzyme production characteristics were analyzed, and then they were applied to the broad bean fermentation simulation system. The protein, peptide, amino acid, amino nitrogen, and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) in the system were evaluated. The results showed that the four microorganisms were Aspergillus oryzae , Aspergillus jensenii , Staphylococcus gallinarum , and Enterobacter hormaeche . Aspergillus oryzae had the highest protease activity at pH 7.0, while the other three strains had better enzyme activity stability under neutral acidic conditions. And the total protein (F1 and F2 were 18.32 g/100 g, 19.15 g/100 g, respectively), peptides (11.79 ± 0.04 mg/g and 12.06 ± 0.04 mg/g), and amino acids (55.12 ± 2.78 mg/g and 54.11 ± 1.97 mg/g) of the fungus experimental groups (F) were higher than the bacterial experimental groups (B). In addition, the enzyme system produced by fungi exhibited a stronger ability for albumin (20 kDa) and glutenin (<30 kDa) deterioration in neutral conditions, while the bacterial enzyme system was more efficient in degrading albumin (<30 kDa) and glutenin (20–30 kDa) in acidic conditions, as indicated by SDS‐PAGE. These findings showed that both bacteria and fungi played an important role in the degradation of protein in different fermentation stages of broad bean fermentation. Practical applications There is a lack of comprehensive understanding of the protein composition and protein degradation mechanism of broad beans in the fermentation stage of PXDB. This research work explored the differences in the degradation of PXDB fermented protein by different microorganisms, and provided a theoretical basis for optimizing the production of PXDB and improving the quality of PXDB.

BackgroundIn this study, different proportions of soybean flour and gluten flour were used to partially replace wheat flour for the fermentation of PXDB (Pixian Douban)‐Meju. The aim was to study the effects of soybean flour/gluten flour on the quality improvement of PXDB.ResultsComparing with the control group (CT), the amino acid nitrogen was improved by 3.8%, 5.6%, and 9.4% in the substitution degree of 12.5% (soybean flour, H2), 7.5% (gluten flour, G2), and 10% (gluten flour, G3). The mixture of wheat flour and gluten flour (G2, G3) could both raise the contents of organic acids and free amino acids. GC×GC‐MS results showed that the amount of key aroma substances increased about sixfold compared to the CT group (194.61 g/kg), achieving 1283.67, 1113.883 and 1160.19 g/kg for H2, G2 and G3 groups, respectively. Moreover, there were more favorable accumulation of aldehydes and pyrazines in all the substitution groups. Quantitative descriptive analysis indicated that the G3 sample presented the best organoleptic quality with reddish‐brown color and more mellow aroma than the control sample.ConclusionIn conclusion, the fermentation of G3 resulted in a higher quality of PXDB‐Meju, showing that partial substitute of wheat flour with gluten was facilitated for improving the quality of PXDB.This article is protected by copyright. All rights reserved.