Sunflower seeds, oil, and protein powder are rich in nutritional value, but the quality of different varieties of sunflower seeds is quite different, and the comprehensive comparative analysis characteristics of edible and oil sunflower seeds are still unclear. The comprehensive analysis and comparison of the raw material indicators, physicochemical properties, and processing characteristics of four edible and four oil sunflower seed varieties were investigated. The results showed that the engineering properties, texture characteristics, single-cell structure, and oil, protein, and starch granule distribution were different between edible and oil sunflower seeds. The composition of fatty acids and amino acids was different among edible, oil sunflower seeds and different varieties. The oleic acid (18.72~79.30%) and linoleic acid (10.11~51.72%) were the main fatty acids in sunflower seed oil, and in amino acid composition, the highest content was glutamic acid (8.88~11.86 g/100 g), followed by aspartic acid (3.92~4.86 g/100 g) and arginine (4.03~4.80 g/100 g). Sunflower meal proteins were dominated by 11S globulin and 2S albumin, and the secondary structure was dominated by β-folding, with -SH and S-S varying greatly among different varieties. Sunflower meal proteins vary widely in terms of functional properties among different varieties, and specialized quality screening was necessary. This study provided a reference and theoretical support for understanding sunflower seeds to further promote the processing and utilization of sunflower seeds.

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.