Unlocking the potential of melon seed protein: enzymatic hydrolysis and functional characterization of protein hydrolysates

Melon seeds are a protein-rich byproduct that remains underutilized. This study investigated the production and functional properties of protein hydrolysates from melon seed protein using six proteases: papain, bromelain, neutral protease, alkaline protease, pepsin, and trypsin. The hydrolysates were evaluated for antioxidant activities and α-amylase inhibition. Neutral protease hydrolysates exhibited the strongest DPPH radical-scavenging activity, with the lowest IC50 value of 0.72 ± 0.03 mg·mL−1, while papain hydrolysates showed the strongest hydroxyl radical-scavenging activity, with an IC₅₀ value of 5.08 ± 0.36 mg·mL−1. Trypsin hydrolysates exhibited the strongest α-amylase inhibitory activity, with the lowest IC₅₀ value of 0.50 ± 0.04 mg·mL−1. Selected hydrolysates showed good pH and thermal stability, with higher oil-holding than water-holding capacity. Ultrafiltration revealed enhanced bioactivities in the <3 kDa fractions. These findings highlight the potential of enzymatic hydrolysis to convert melon seed protein into functional protein hydrolysates, thereby supporting the high value utilization of plant-derived protein resources.