Structural characteristics, processing stability, and antioxidant activity of peptide-zinc chelates from pumpkin seed...

Protein-rich pumpkin seed meal is often discarded or used as low-value feed, wasting resources. To valorize protein resources from this by-product, five types of novel pumpkin seed peptide‑zinc chelates (PSPHs-Zn) were synthesized in this study. The zinc chelating capacity, structural characteristics, processing stability, and antioxidant activity of PSPHs-Zn were systematically compared. Among them, PSPH-Aci (from acidic protease hydrolysate) exhibited the highest zinc chelating capacity (134.88 mg/g), an antioxidant amino acid (Trp, Arg, etc.) content of 28.38%, and a DPPH radical scavenging rate of 72.57%. This chelate retained over 90% of zinc after pasteurization and showed little change in zinc retention under high salt conditions (≤ 6% NaCl) and at pH 3.0-6.0. Moreover, the thermal stability of PSPH-Pro-Zn (zinc chelate from composite protease hydrolysate) (ΔH = -135.42 J/g) was superior to that of the conventional supplement zinc glycinate. These findings offer a viable strategy to valorize pumpkin seed meal as a by-product.