Influence of polysaccharides on the rheology and stabilization of α-pinene emulsions

• We compare the performance of gellan and xanthan gums as pinene emulsion stabilizers.
• Gellan, xanthan and a mixture of both gums eliminate creaming but not coalescence.
• Rheology shows that xanthan and gellan mixtures yield thermodynamic incompatibility.
• Destabilization of pinene emulsions is monitored by multiple light scattering.
• Destabilization of pinene emulsions is modelled by a first-order kinetic equation.

This work focuses on the need to include polysaccharides in a slightly concentrated O(α-pinene)/W emulsion, formulated with amphiphilic copolymers as emulsifiers. Rheology, laser diffraction and multiple light scattering were the main techniques used to assess the performance of gellan gum, xanthan gum and a mixture of both hydrocolloids as stabilizers. Small amplitude oscillatory shear results were consistent with the existence of three distinct microstructures and relaxation mechanisms, which depended on the hydrocolloid system used. The mechanical spectrum of the emulsion containing both polysaccharides signalled the occurrence of thermodynamic incompatibility between the two. Flow curves fitted to the Carreau–Yasuda model demonstrated a negative synergistic effect between gellan and xanthan gums. The droplet size distribution was similar for these systems, which highlighted the importance of the continuous phase for emulsion stability. Multiple light scattering illustrated that creaming was practically eliminated by the incorporation of polysaccharides, coalescence being the main destabilization mechanism.