The discoloration mechanism of Antarctic krill oil based on the model systems: Astaxanthin fading mediated by phospholipid reverse micelle interfaces.

Astaxanthin fading is a critical quality defect in Antarctic krill oil (AKO), potentially associated with reverse micelles (RMs) formed by phospholipids. The oxidative fading behaviors of four carotenoids were compared in medium-chain triglyceride (MCT)-based systems with or without phosphatidylethanolamine (PE). PE markedly accelerated the fading of strongly polar astaxanthin and canthaxanthin (retention decreased to 22.46 ± 1.49% and 29.03 ± 2.51%, respectively), but had limited effects on β-carotene and lycopene. Cryo-TEM and SAXS showed that PE could self-assemble into nanoscale RMs, while CLSM and interfacial analyses indicated that strongly polar carotenoids were anchored at the RM interface. This interfacial localization increased the oxidative exposure of strongly polar carotenoids, thereby accelerating their degradation and color fading. This study reveals the RM interface as an important microenvironment governing polarity-dependent carotenoid fading and provides a mechanistic basis for improving the color stability of AKO.