Self-aggregated chitosan particles are a promising candidate in stabilizing food-based Pickering emulsions because they are naturally-derived, edible, and inexpensive. However, there are limited studies on the use of chitosan particles as a solid emulsifier in forming oil-in-water (O/W) emulsions. In this study, the self-aggregated chitosan particles were synthesized from chitosan solution with and without ultrasonication pretreatment. The physicochemical and emulsifying properties of the chitosan particles formed were investigated. Ultrasonication pretreatment caused depolymerization of chitosan, resulting in the formation of smaller and monodisperse chitosan particles, compared to the non-pretreated chitosan. The confocal microscopy images reveal that both types of chitosan particles could be adsorbed at the oil–water interface. Interestingly, the particles produced from non-pretreated chitosan formed smaller emulsion droplets and they caused less creaming after 7 days of storage, compared to the emulsions stabilized by the particles synthesized from the pretreated chitosan. These findings suggest that ultrasonication pretreatment on chitosan could reduce the hydrophobicity of the chitosan particles formed via self-aggregation, as confirmed by the contact angle measurement. Despite this, both types of chitosan particles were able to form Pickering emulsions up to 70% v/v oil loading at a low chitosan concentration of 0.1% w/v. The emulsions formed were also stable against droplets coalescence during storage. These results show the potential of self-aggregated chitosan particles as Pickering emulsifier for stabilizing food emulsions.
