Abstract
Background: Emulsion-based formulations have gained attention in food and pharmaceutical products due to their unique properties. However, their use in food product formulation faces problems because of phase separation and fat oxidation, which seriously reduces the quality of the product. Therefore, finding ways to increase the physical and oxidative stability of emulsions is valuable. This work aimed to assess of physicochemical properties of sodium caseinate (SC)-tannic acid (TA) complex treated with heating and ultrasonication as well as their efficiency in physical and oxidative stability of high internal phase Pickering emulsion (HIPPEs) as antioxidant colloidal particles.
Methods: SC 1% (w/v) was mixed with a different concentration of TA (0.1, 0.3, 0.5, 0.7, 1% w/v) and the pH of solutions was adjusted to 9. The unheated, heat-treated, and ultrasonicated SC-TA complexes were analyzed to elucidate possible interaction using FTIR, fluorescence spectroscopy, and DSC. Finally, HIPPEs were prepared by mixing the prepared samples and soybean oil at a volume ratio of 25:75 v/v respectively. The microstructure of the most stable HIPPEs was assessed using SEM.
Results: Based on the FTIR results the covalent bond in heat-treated SC-TA was formed via the Maillard reaction. In addition, the reduction of free amino groups confirms Schiff base formation. All treated SC-TA samples showed a superior ability to stabilize emulsion in comparison with native SC when used as an aqueous phase of HIPPEs. The long-term physical was observed in heat-treated SC-TA HIPPEs for over two months. In PEs stabilized by SC-TA complex nanoparticles, primary and secondary oxidation product levels were significantly lower than in SC alone.
Conclusion: The fabricating antioxidant emulsions using heat-treated SC-TA are a good guarantee for the physical and oxidative stability of food formulations due to TA's intrinsic antioxidant properties and the protective role of SC-TA colloidal particles against coalescence.