Effects of novel and conventional thermal treatments on the physicochemical properties of iron-loaded double emulsions

In this work, changes in different physicochemical properties of iron-loaded double emulsions (DEs) were monitored under the influence of novel (microwave and ohmic) and conventional heat treatments. Microwave heating led to destabilization and obvious phase separation. As compared to control samples, heat treatment increased particle size, light absorbance, centrifugal instability, iron expulsion from the internal aqueous phase, color difference, chemical instability of the lipid phase, release of iron in simulated gastrointestinal fluids and iron bioavailability in cell line SW742. Emulsion viscosity and whiteness index decreased after heat treatment, whereas the zeta-potential remained unchanged. There was a negative correlation between physicochemical stability and heat treatment intensity. Conventional heating resulted in greater stability than ohmic heating. Yoghurt samples (as model systems) were fortified with either iron-loaded or iron-free DEs. Our results showed that the presence of iron in the aqueous phase resulted in significant lipid oxidation during storage.