Enhancing the oxidative stability of food emulsions with rice dreg protein hydrolysate

Rice dreg protein hydrolysates (RDPH) can potentially be used as natural antioxidants for a variety of emulsion-type food systems. They contained 89.9% protein, 934.2 mg/g total amino acids with 517.7 mg/g total hydrophilic amino acids, and 78% peptides smaller than 5 kDa. Here, the physical and oxidative stabilities of corn oil-in-water emulsions (10 wt.% lipid) containing RDPH (0-20 mg/mL) and stabilized by Tween-20 were investigated as a function of RDPH concentration and pH. The results showed that emulsions with RDPH and Tween-20 emulsions did not experience coalescence (when RDPH concentration < 20 mg/mL), and were more stable than emulsions prepared by either emulsifier alone (RDPH or Tween-20). RDPH and Tween-20 could not prevent coalescence, because when RDPH = 20 mg/mL, competitive adsorption existed at the interface between high concentrations RDPH and Tween-20. The negatively charged emulsion stabilized with 5 mg/mL RDPH and Tween-20 was found to be more stable at pH 5. RDPH was able to inhibit lipid oxidation, reducing the formation of lipid hydroperoxides and TBARS with increasing RDPH concentrations. Similarly the increase in pH also reduced oxidation, possibly by scavenging free radicals and chelating pro-oxidant metals. The antioxidant properties of RDPH at the interface of emulsion droplets would render them suitable as natural antioxidants in some food products.

► Stable corn oil-in-water emulsions could be formed with RDPH assisted by Tween-20. ► Emulsion stabilized with 5 mg/mL RDPH and Tween-20 was more stable at pH 5. ► RDPH can be used as natural antioxidant for emulsion-type foods. ► RDPH was able to inhibit lipid oxidation with increasing RDPH concentrations and pH.