Abstract: In this paper, a umami peptide was isolated and purified from air-dried and fermented Megalobrama amblycephala using ultrafiltration, nanofiltration and reversed phase high performance liquid chromatography (RP-HPLC). The umami taste was measured with an electronic tongue. Matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), an automatic amino acid analyzer and Fourier transform infrared spectroscopy (FTIR) were used to measure the molecular mass, amino acid composition and secondary structure of the umami peptide and furthermore, we investigated the relationship between structure and umami taste. The results showed that a single umami peptide P2a-2 with a molecular mass of 1 304.59 Da was obtained and identified. Moreover, the umami amino acids glutamic acid (21.97%), alanine (10.67%) and glycine (9.51%), as well as the umami enhancer histidine (27.54%) were found in P2a-2, and the secondary structure was beta-turn (90.16%). We deduced that P2a-2’s strong umami taste may be due to the high content of umami amino acid and beta-turn structure.

Key words: air-dried and fermented Megalobrama amblycephala, peptide, umami, purification, secondary structure