One-step ultrasound producing O/W emulsions stabilized by chitosan particles

Highlights

• One-step ultrasound was used to produce chitosan nanoparticles and O/W Pickering emulsions.

• Chitosan particles size reduced and hydrophobicity increased at more drastic process conditions.

• Chitosan particles present surface activity at neutral pH.

• Bridging flocculation occurred between adsorbed particles onto the droplet interface.

• Interactions between droplets resulted in network formation that avoided the emulsion destabilization.

Abstract

Deprotonated chitosan nanoparticles have shown a potential to act as a food-grade particle stabilizer of oil-in-water (O/W) Pickering emulsions. The effect of one-step emulsification conditions using ultrasonic device was studied changing time and ultrasonication (US) power. The physicochemical properties of chitosan particles and O/W Pickering emulsions produced at the same time from different process conditions were evaluated. The surface activity of chitosan particles was evidenced with the reduction of interfacial tension between oil-water phases. This behavior was associated to the great capacity of hydrophobic groups acting onto the interface during the ultrasonic emulsification. The combined intensification of time and US power also led to an increase of hydrophobicity and polydispersity, changes in zeta potential and reduction on size of chitosan particles. At higher US power, the decrease of droplet size favored the interaction between oil droplets through weak attractive forces and particles sharing (bridging flocculation) leading to an increase in viscosity of emulsions. Thus, the major finding of this work was to elucidate the emulsion stability mechanism by deprotonated chitosan particles, which was associated to an increase of their hydrophobicity and the formation of a droplet network structure. In addition, a one-step homogenization could be performed allowing to produce these emulsions using less energy and process time.