Inhibition of lipid oxidation in nanoemulsions and filled microgels fortified with omega-3 fatty acids using casein as a natural antioxidant

The susceptibility of omega-3 fatty acids to oxidation in foods can often be retarded using well-designed colloidal delivery systems. In this study, the ability of a natural antioxidant (casein) to inhibit the oxidation of flaxseed oil in oil-in-water nanoemulsions and filled hydrogel beads (microgels) was investigated. Nanoemulsions (D-43 = 0.31 mu m) were fabricated by high-pressure homogenization using a quillaja saponin extract (Q-Naturale) as an emulsifier, whereas filled microgels (D43 = 970 gm) were fabricated by injecting a 0.8% alginate solution containing nanoemulsions into a calcium solution using an extrusion device. The size of the particles in these colloidal delivery systems exhibited no major changes during 14-days storage at 55 degrees C. The oxidative stability of flaxseed oil droplets was better when they were encapsulated in microgels than when they were free, which was attributed to the greater surface area of exposed lipid in the latter case. The oxidative stability of both nanoemulsions and filled microgels was improved by adding caseinate as an antioxidant. Simultaneous incorporation of both caseinate and lipid droplets within microgels proved to be the most effective means of inhibiting lipid oxidation. Overall, these results provide valuable information for the development of colloidal delivery systems to encapsulate and protect omega-3 fatty acids for functional food applications. (C) 2016 Elsevier Ltd. All rights reserved.