Structure and stability of W₁/O/W₂ emulsions as influenced by WPC and NaCl in inner aqueous phase

Effect of WPC and NaCl in internal aqueous phase (W₁) of W₁/O/W₂ type double emulsions was studied. Pre-emulsion and final emulsion were prepared using microfluidizer and Ultra-Turrax high shear mixer, respectively. The emulsions prepared using salt exhibited uniform droplet size distribution and structural integrity. WPC at 6% and NaCl at 2 or 4% levels demonstrated better sedimentation stability (> 99%) and encapsulation stability (> 95%) during preparation and storage of double emulsions. Samples without added NaCl showed poor emulsion stability and structural integrity. Higher level of WPC i.e. 8% resulted in poor stability and encapsulation efficiency of double emulsions at all salt levels. Combined use of optimum levels of WPC and NaCl along with processing interventions resulted in stable double emulsions even after storage at room temperature for 10 days. This study highlights the fact that structural integrity of internal aqueous phase (W₁) depends upon presence of osmotic agent i.e. salt and stabilising proteins i.e. WPC.