Improved oxidative stability and sensory acceptability of omega-3–fortified kefir using whey protein–stabilised fish oil nanoemulsions

Abstract This study assessed whey protein isolate (WPI)–stabilised fish oil nanoemulsions (FO-NEs) to improve oxidative stability and sensory properties of omega-3–fortified kefir. FO-NEs (10% w/w oil), produced by high-pressure microfluidisation, were incorporated into kefir and evaluated against bulk FO during 21 days at 4°C. At day 14, when peroxide values reached their maximum, NE-fortified kefirs showed lower peroxide values (0.015–0.021 mM) than bulk systems (0.028–0.033 mM), corresponding to a 36–46% reduction in primary oxidation. In contrast, p-anisidine values reached their highest measured levels on day 7, and baseline-corrected increases from day 0 to day 7 were 90.0% and 55.6% lower in the unflavored and flavored FO-NE-fortified kefirs, respectively, than in their corresponding bulk-FO formulations. Particle size increased during storage, with similar values between samples suggesting matrix-induced aggregation rather than droplet coalescence. ζ-potential decreased from −25.0 to −12.4 mV with minor pH changes. A preliminary consumer test using a semi-trained panel suggested higher acceptability for flavored NE-fortified kefir compared with other formulations. WPI-stabilised FO-NEs reduced lipid oxidation while maintaining physicochemical and sensory properties.