Isolation, identification and characterization of taste peptides from fermented broad bean paste

Pixian broad-bean paste (PBBP) is a famous fermented condiment in China, which may produce abundant flavor peptides during the fermentation process. Herein, the flavor peptides from fermented broad-bean (FB) were separated and identified via ethanol precipitation, macroporous resin, and ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) methods. The results showed that there were fifteen novel flavor peptides in FB. Among them, six peptides (i.e. ALDELGT, AELTPEP, SAALQAG, SFEAVEAAPT, EQDNDGNNIFSGFKR, QTFNTEEDTAK, and DAPASGN) were perceived umami with threshold values ranging from 0.76 to 1.84 mmol L^-1. And they had both salty-enhancing and umami-enhancing abilities. Meanwhile, novel peptides (i.e. GGLRIINPEGQQ, SIITPPERQ, GGLSIITPPERQA, GGLRIINPEG, SIITPPER, RIINPEGQQ, DALNVNRHIV, and LPKILLLQLV) were perceived bitter with threshold values ranging from 0.56 to 2.89 mmol L^-1. And the monosodium glutamate (MSG) solution had a certain masking effect on bitter peptides. GFSSEFLA showed a strong sweet taste. From peptide sequence analysis, it was found that Aspergillus oryzae and broad-bean were important taste-active sources of the flavor peptides in FB. Besides, the synthetic peptides showed a much better sensory taste than the mixtures of the corresponding amino acids. It indicated that peptides might play an important role in deciding the taste of FB. Significantly, it is the first time that the isolated flavor peptides were identified from FB.