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The presentation of high pressure processing (HPP) on corn starch has been reported, but the effect on protein in corn gluten meal (CGM) is rarely explored. The purposes of this study were to investigate the effect of HPP treatment on structural and functional properties of the protein in CGM. Protein was treated at 200–600 MPa for 5–15 min. Results showed that HPP treatment increased protein solubility, water and oil binding capacities, emulsion stability, foaming and foam stability. Protein which treated at 400 MPa for 15 min had the more enhanced functionality. Moreover, under this condition, the protein aggregates gradually dissociated, and the particle size decreased. These results indicated that the functional groups and structure of CGM protein were affected by the HPP treatment. We hope to convert an underutilized material into a valuable one through HPP in food industry.

Oats (Avena sativa L.) with similar amylose content were used to investigate the effects of ultra-high pressure treatment (UHPT) on the eating quality of steamed oat and oat protein structure. Water absorption and texture of steamed oat were evaluated and taste analysis was conducted by electronic tongue after a series of UHPT (400–600 MPa; holding time 5–15 min). The oat protein was extracted from the oat and treated with the same UHPT as the steamed oat (400–600 MPa; holding time 5–15 min). The oat protein structure was scanned by scanning electron microscopy (SEM). The water absorption rate of oat rice was increased by UHPT. Hardness values of steamed oat were reduced while springiness and cohesiveness were increased by UHPT. The UHPT samples showed significant differences in electronic tongue profiles from that of the original samples. The SEM results indicated that the structure of the protein was greatly affected by UHPT. The impact on protein structure significantly increased with an increasing level of pressure and treatment time. In general, the UHPT has strong potential to improve the texture and flavor of oat and change the structure of oat protein during industrial production.

In order to isolate antioxidant peptides from oats globulin hydrolyzed alcalase, an antioxidant peptide was isolated and purified using ultra-filtration and ion-exchange chromatography. Hydroxyl and 1,1-diphenyl-2-pycrylhydrazyl (DPPH) radical scavenging capacity was analyzed to evaluate the antioxidant activity of peptide. Five fractions were obtained after ultra-filtration, fraction with molecular weight >10KDa showed the strongest hydroxyl and DPPH radical scavenging ability of 58.38 ± 0.87% and 24.53 ± 0.53% (p < 0.05). Fraction C which was purified via ion-exchange chromatography, exhibited the maximum antioxidant activity (IC50 of hydroxyl and DPPH radical scavenging ability was 1.83 ± 0.03 mg mL−1 and 4.11 ± 0.07 mg mL−1) among other fractions (p < 0.05). Subsequently, five antioxidant peptides were identified by electrospray ionization mass spectrometry (ESI-MS/MS), with the amino acid sequence of IRIPIL, FLKPMT, NSKNFPTL, LIGRPIIY, and FNDILRRGQLL, with a molecular weight of 723.50, 735.40, 919.48, 943.59, and 1343.76 Da, respectively.

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.

Glutelins derived from oats were purified and hydrolyzed sequentially using alcalase proteases for production of antioxidant peptides. The antioxidant activities of oat glutelin peptides were evaluated using reducing power methods including hydroxyl and 1,1-diphenyl-2-pycrylhydrazyl (DPPH) radical-scavenging assays. The results demonstrated that oats glutelin peptide D-1a exhibited the highest antioxidant activity compared to the other hydrolysates. D-1a was identified to be His–Tyr–Asn–Ala–Pro–Ala–Leu (784.38 Da) by electrospray ionization mass spectrometry (ESI-MS/MS).