Modification of Oxalis tuberosa starch with OSA, characterization and application in food-grade Pickering emulsions

The emulsifying properties of Oxalis tuberosa starch (native and chemically modified) were evaluated in Pickering emulsions based on the emulsification index, emulsion stability over time and emulsion morphology. The best conditions of chemical modification were found by esterification of starch with octenyl succinic anhydride (OSA) at a concentration of 3% and a reaction time of 2 h, achieving a degree of substitution of 0.033 ± 0.001. The results obtained using Fourier-transform infrared spectroscopy, a Rapid Visco Analyzer, and differential scanning calorimetry, indicated that the starch underwent a change in its structure and that the insertion of the OSA groups was achieved. The amphipathic characteristics of OSA starch were evaluated by forming oil-in-water emulsions. Various concentrations of OSA-starch granules (1, 2.5 and 5 wt%) were used. A higher concentration of particles produced a smaller droplet size of emulsions (76.5 ± 0.9 μm) compared to those formed at a lower concentration of 1% (92.5 ± 1.0 μm). Therefore, the starch modified with OSA displayed the necessary characteristics to be adsorbed at the oil-water interface, achieving Pickering emulsion stabilization.