In situ precipitation enhances emulsifying performance of polysaccharides.

Abstract

Polysaccharides offer biodegradable and sustainable means of stabilizing emulsions. However, to be effective they often need surface modification or addition of surfactants, compromising their overall environmental and economic viability. We present an alternative approach by leveraging the solubility window of polysaccharides in alkaline or acidic environments. By modulating pH, polysaccharides are dissolved and subsequently partially precipitated, yielding a controlled coexistence of soluble chains and precipitated particles, quantified via mass-based solubility measurements. Emulsification at a partially precipitated stage produces emulsions with enhanced microstructure compared to "As-received" polysaccharides at neutral pH. Subsequent in situ pH neutralization further confines polysaccharide precipitation within the narrow aqueous channels between droplets, forming a mechanically stable particle-particle and particle-droplet network, as evidenced by enhanced viscoelastic moduli and reduced droplet coalescence. Using enzymatically polymerized α-1,3-glucan and β-1,4-chitosan from aquaculture, we demonstrate the versatility of this method, providing a practical approach for polysaccharide-based emulsion engineering.