Effect of metal-chelating peptides and pea protein hydrolysates on lipid oxidation

Abstract: Lipid oxidation naturally occurs in oil-in-water emulsions, and synthetic antioxidants are commonly used in lipid-rich foods to avoid this phenomenon. Yet, due to their questioned toxicity and consumers awareness, there is a growing trend for natural ingredients to replace them. Also, the effect of bioactive peptides produced from protein hydrolysis on lipid oxidation could be an interesting alternative to explore. The metal-chelation properties of some peptides present in protein hydrolysate is related to their antioxidant properties. Indeed, while complexing transition metal ions, metal-chelating peptides (MCPs) could prevent Fenton- and Haber-Weiss-like reactions and thus delay/inhibit the oxidation phenomena, notably in food emulsion systems. Our group aim to screen the presence of MCPs in protein hydrolysate, separate and identify them and further investigate their antioxidant activity for further industrial applications. After a brief overview of the various approaches developed by our team, we will focus on the effect of MCPs and pea protein hydrolysate on the inhibition of lipid oxidation in oil-in-water emulsion. Supplemented with peptides, pea hydrolysate, EDTA or carnosine as reference, O/W emulsions were characterized for their physical stability and oxidative stability. The measurement of creaming, droplet size, zeta potential of emulsions show their physical stability due to the efficient emulsifier used (Tween® 20) and the peptide/hydrolysates addition in the emulsion does not affect their physical stability. Besides, concerning their oxidative stability, emulsions containing peptides/hydrolysates have a good ability to inhibit formation of primary oxidation products compared to the negative control emulsion, and are able to slow down lipid oxidation by chelating Fe²⁺. Thus, MCPs and hydrolysates are a promising alternative to synthetic antioxidant commonly used in industrial products to inhibit the lipid oxidation. More, their screening based on metal-chelation properties – notably using SPR - are appropriate to select the most pertinent sample to further investigate on lipid oxidation.