Molecular Weight-Dependent Functional and Antioxidant Properties of Glutamine-Rich Corn Protein Hydrolysate: Insights into the Predicted Structural Characteristics of Identified Peptides

In this study, corn protein hydrolysates (CPT) were prepared via enzymatic hydrolysis using Alcalase and Protamex, and then fractionated by ultrafiltration into three molecular weight components: >5 kDa (CPT1), 3–5 kDa (CPT2), and <3 kDa (CPT3). The physicochemical, functional and in vitro antioxidant properties of each component were systematically compared. Subsequently, glutamine peptides were isolated and identified from CPT3 using LC-MS/MS technology, and the structural characteristics of the identified peptides were further analyzed. The results showed that the ultrafiltration fractionation effectively enriched peptides with lower molecular weights from the enzymatically hydrolyzed products, which may potentially enhance their bioavailability. In addition, CPT3 exhibited superior foaming ability, emulsifying ability, dispersibility, and zeta potential, along with lower particle size and viscosity. Moreover, CPT3 exhibited strong antioxidant activity, with IC50 values for ABTS radical scavenging and hydroxyl radical scavenging of 0.042 ± 0.003 mg/mL and 0.807 ± 0.019 mg/mL, respectively. Finally, 205 glutamine peptides were further identified from CPT3, and their structural characterization revealed that the identified peptides were rich in hydrophobic amino acids and had a high affinity for membrane proteins, which could serve as potential ligands for regulating intestinal barrier dysfunction. In summary, CPT3 possesses excellent functional properties and antioxidant activity, indicating its potential for development and application in functional and health foods.