Impact of chitosan/metal oxide-based blends on the rheology, stability, and microstructures of oil-in-water emulsions

In this study, chitosan and metal oxides, specifically copper oxide, zinc oxide, and a combination of both, were used to prepare blends. These blends were utilized to stabilize 40 wt % oil-in-water emulsions with 1 wt % blend at pH 4. The results obtained from scanning electron microscopy and transmission electron microscopy analyses revealed that the chitosan/zinc oxide (CS/ZnO) and chitosan/copper oxide/zinc oxide (CS/CuO/ZnO) combinations exhibited smooth, non-porous, and spherical surfaces in comparison to other systems. This behavior of CS/ZnO and CS/CuO/ZnO has improved the surface morphology of these blends. The CS/CuO emulsion exhibited significantly larger particles (11 μm, p < 0.001) and a higher creaming index (CI = 24%, 30 days of storage) compared to other emulsions. Additionally, the CS/ZnO emulsion had significantly higher viscosity and moduli (p < 0.01) at applied rates and frequencies compared to other emulsions, suggesting a predominantly elastic and compact structure in CS/ZnO emulsion.