Characterizations of oil-in-water emulsion stabilized by different hydrophobic maize starches

The molecular structure, rheological properties, microstructure and physical stability of oil-in-water emulsions using octenyl succinic-sugary maize soluble starch (OS-SMSS) were investigated and compared with two commercial OS-starches (HI-CAP 100 and Purity Gum 2000). The degree of substitution (DS), weight-average molecular weight (Mw) and z-root mean square radius of gyration (Rz) of OS-SMSS, HI-CAP 100 and Purity Gum 2000 were 0.0050, 223.4×10⁵g/mol and 38.8nm, 0.0037, 9.6×10⁵g/mol and 29.3nm, and 0.0031, 31.3×10⁵g/mol and 39.6nm, respectively. FT-IR spectra showed two new absorption bands at 1725 and 1570cm^-1 from OS ester linkage in all tested samples. The emulsion with OS-SMSS exhibited a pseudoplastic behavior over the whole shear rate range, whereas other two emulsions showed a similar Newtonian fluid. All hydrophobic starch stabilized emulsions satisfied the Herschel-Bulkley model. All emulsions displayed storage modulus (G') was higher than loss modulus (G″), and only G' and G″ of OS-SMSS stabilized emulsion were independent of frequency. The volume-average droplet size (d₄₃) value of emulsions stabilized by three modified starches was 27.9, 15.2 and 24.4μm, respectively. During 4 weeks storage, lower change in d₄₃ of emulsion with OS-SMSS was observed. The above results with schematic models of emulsions suggested that an emulsion with high stability could be prepared using 3% of OS-SMSS due to the formation of high density and thick nanoparticle layer at the interface, indicating OS-SMSS was a Pickering emulsion stabilizer for good long-term stability.