Sensory and structural characterization of umami peptides derived from sunflower seed

Umami peptides were derived from enzymatic hydrolysis of sunflower seed protein, followed by isolation and identification. The flavourzyme-enzymatic hydrolysates exhibited the highest umami intensity value of 10.72 ± 0.05 and the lowest bitterness, when pH was adjusted to 7.0, the flavorzyme was added at enzyme-to-substrate (E/S) ratio of 1:25 (w/w), then incubated in a temperature-controlled water bath at 55°C, and the hydrolysis time was 480 min. Ultrafiltration, gel filtration chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC) were used to isolate the umami peptides of sunflower seed. Five fractions were obtained after ultra-filtration, fraction with molecular weight 1-3 kDa showed highest umami intensity value 13.93 ± 0.06. Fraction F1, which was purified via sephadex gel filtration chromatography, exhibited high umami value (12.21 ± 0.06), and low bitterness (4.57 ± 0.06). Seven sub-fractions were purified by RP-HPLC, and the umami taste value of F1-4 was the highest (14.16 ± 0.05), which was 1.32 times stronger than that of sunflower seed protein hydrolysates without any purification. Furthermore, the structure of fraction F1-4 was characterized by mass spectrometry, and three peptide fractions were identified, with amino acid sequences of DVNNPANQLD, NNENQLDEYQR, and EFEGGSIEH, respectively.