Effects of environmental factors on the physical stability of pickering-emulsions stabilized by chitosan particles

Oil-in-water (O/W) Pickering emulsions stabilized by food-grade particles have gained increasing research attention recently. The aim of the present study was to investigate the effects of chitosan concentration and environmental factors i.e., ionic strength, temperature, and pH on the physical stability of the emulsions stabilized by self-aggregated chitosan particles. The emulsions were prepared using a high speed homogenizer and their coalescence, creaming, and flocculation stability was evaluated. Increasing the chitosan concentration from 0.01 to 0.3% w/v was found to enhance the coalescence and creaming stability. Similar results were obtained with the addition of NaCl from 100 to 500 mM. The emulsions were also highly stable at pH 7 and above. Reducing the pH was found to promote droplets coalescence and creaming, with demulsification occurring at pH 2. The emulsions were stable at and below 50 °C. Increasing the temperature was found to promote droplets coalescence and creaming. The improvement in the emulsion stability could be attributed to the aggregation of particles at the O/W interface and the formation of chitosan networks in the continuous phase, thus limiting droplet–droplet interactions. In conclusion, the physical stability of Pickering emulsions stabilized by chitosan particles was found to be responsive to environmental stimuli. This feature could be exploited in the development of stimulus-responsive emulsions for food or pharmaceutical applications.