Antioxidants location affects the oxidative stability of spray-dried microcapsules loaded with fish oil

Abstract

The oxidative stability of fish oil-loaded capsules (~15 wt% oil load) produced by spray-drying and containing natural antioxidants of different polarity was investigated. For this purpose, three commercial rosemary extracts (e.g., water-dispersible; K1 or oil-soluble; K2, K3) and whey protein concentrate hydrolysate (WPCH), exhibiting surface-active properties, were evaluated. The capsules showed similar physicochemical properties (e.g., morphology, size and encapsulation efficiency >91%), regardless of the formulation. However, the polarity of the antioxidant used significantly influenced the oxidative stability. The microcapsules containing hydrophobic antioxidants showed the lowest peroxide value (PV) after drying, followed by the WPCH-containing capsules, although the PV evolution over storage was similar among the samples. Nonetheless, WPCH was the most effective antioxidant reducing the formation of volatile secondary oxidation products in the capsules. This was attributed to its partition at the oil/matrix interface, resulting in an enhanced protective effect when combined with tocopherols present in the encapsulated oil.