Influence of iron, calcium, and zinc on the oxidative stability of omega-3 fatty acids in pea protein-stabilized oil-in-water emulsions.

BACKGROUND

Plant-based emulsified foods fortified with omega-3 fatty acids and minerals are nutritionally attractive, but their formulation is challenging because alpha-linolenic acid (ALA) is highly susceptible to oxidation and some mineral salts may act as pro-oxidants. This study evaluated how iron, zinc, and calcium salts affect pea protein isolate (PPI) properties and ALA oxidative stability in PPI/kappa-carrageenan (KC) gelled emulsions. Treatments included PPI-mineral systems containing ferrous glycinate (FeGly), zinc gluconate (ZnG), calcium gluconate (CaG), calcium lactate (CaL), calcium chloride (CaCl2), or tricalcium phosphate (CaP), and ALA-enriched emulsions evaluated under different pH conditions.

RESULTS

FeGly, ZnG, CaG, CaL, and CaCl2 shifted PPI ζ-potential toward less negative values, whereas CaP showed limited interaction, probably due to its low solubility. Fluorescence spectroscopy confirmed mineral-induced conformational changes. PPI-FeGly and PPI-ZnG increased ABTS+ radical scavenging activity from 42.48% to 50.38% and 47.30%, respectively, while calcium salts reduced or did not improve antioxidant activity. In Rancimat assays, FeGly-containing emulsions showed the highest induction times (20.39 h without tocopherols and 19.62 h with tocopherols), followed by ZnG-containing emulsions (15.06 h). Calcium-containing formulations showed lower stability (7.33-8.43 h), and CaP did not improve oxidation resistance. At pH 7, FeGly and ZnG improved oxidative stability, whereas at pH 3-5 they reduced stability and increased peroxide formation.

CONCLUSION

PPI-mineral interactions can protect or destabilize ALA depending on mineral type, and pH. These findings provide formulation criteria for omega-3 fatty acid and mineral-fortified plant-based gelled emulsions. © 2026 Society of Chemical Industry.