Inhibition of lipid oxidation by encapsulation of emulsion droplets within hydrogel microspheres

The purpose of this study was to assess whether the oxidation of polyunsaturated lipids could be inhibited by encapsulating them within protein-rich hydrogel microspheres (size range 1–100 μm). Filled hydrogel microspheres were fabricated as follows: (i) high methoxy pectin, sodium caseinate, and casein-coated lipid droplets were mixed at pH 7, (ii) the mixture was acidified (pH 5), (iii) casein was cross-linked using transglutaminase, (iv) the pH was adjusted to pH 7. Samples were stored in the dark at 55 °C and were monitored for lipid hydroperoxide formation and headspace propanal. Oxidation of fish oil (1% vol/vol) in the microspheres was compared with that in oil-in-water emulsions stabilised by either sodium caseinate or Tween 20. Emulsions stabilised by Tween 20 oxidised faster than either microspheres or emulsions stabilised by casein, while microspheres and the casein stabilised emulsion showed similar oxidation rates. Results highlight the natural antioxidant properties of food proteins.