Chitosan-Based Conventional and Pickering Emulsions with Long-Term Stability.

Area of Science:

• Colloid and Surface Chemistry
• Materials Science
• Food Science

Background:

• Chitosan is a biopolymer with potential applications in emulsion stabilization.
• Conventional surfactants can have environmental and health concerns.
• Developing surfactant-free emulsion systems is an area of active research.

Purpose of the Study:

• To investigate the ultrasonic generation of chitosan-based oil-in-water (O/W) emulsions.
• To explore the influence of pH on emulsion type, droplet size, and stability.
• To evaluate chitosan as a pH-controlled emulsifier and stabilizer without additives.

Main Methods:

• Ultrasonication was used to generate O/W emulsions using chitosan solutions at various pH values.
• Droplet size was measured using volume average diameter (dv).
• Emulsion stability was assessed over time (up to 5 months).

Main Results:

• Ultrasonication effectively dispersed chitosan and reduced its molecular weight, enhancing emulsification.
• Increasing pH from 3.5 to 5.5 yielded conventional emulsions with smaller droplets and improved stability.
• At pH 6.5, chitosan self-assembled into nanoparticles, forming highly stable Pickering emulsions (dv = 1.7 μm).

Conclusions:

• Chitosan can act as an effective emulsifier and stabilizer for O/W emulsions.
• pH is a critical factor in controlling emulsion type (conventional vs. Pickering) and characteristics.
• Ultrasonically generated, pH-controlled chitosan emulsions offer a promising surfactant-free stabilization strategy.