Controlling the structure and Pickering emulsion stability of OSA starch nanoparticles by varying the ratio of...

Green and non-toxic choline glycine ([Cho][Gly]) ionic liquid (IL) was explored as a good solvent for nanoprecipitation to prepare octenyl succinic anhydride (OSA) starch nanoparticles (OSNPs) as Pickering emulsifiers. Then the regulation of water/ionic liquid (W:IL) ratios on the structural characteristics of OSNPs and the impact of these characteristics on the stability of Pickering emulsions were elucidated. Compared to water (W:IL-10:0), OSA starch (OSAS) molecules in a low [Cho][Gly] concentration solution (W:IL-8:2) showed enhanced aggregation behaviors (indicated by an increased G' value), allowing more OSA moieties and starch molecules to be involved in the nucleation of OSNPs. This led to the formation of larger, less hydrophobic OSNPs with reduced emulsifying ability. Conversely, moderate [Cho][Gly] concentrations (W:IL-6:4 and 4:6) suppressed OSAS aggregation (leading to lower G' values), yielding smaller, more uniform, and more hydrophobic OSNPs. These structural characteristics of W:IL-6:4 and 4:6-OSNPs facilitated the formation of dense interfacial layers, which effectively prevented droplet aggregation and enabled exceptional emulsion stability for 21 days, notably for W:IL-6:4-OSNPs. However, as [Cho][Gly] concentrations increased further (W:IL-2:8 and 0:10), the significantly higher viscosity of these [Cho][Gly] solvents would cause the aggregation of OSNPs during nanoprecipitation, producing much larger particle sizes of W:IL-2:8 and 0:10-OSNPs and consequent reductions in emulsion stability compared to lower concentrations. These findings will provide a basis for the rational design of starch nanoparticles using [Cho][Gly] solvents to meet the requirements of Pickering emulsion.