Effect of homogenization and surfactant type on the exchange of oil between emulsion droplets

The goal of the research was to determine the effects of homogenization and surfactant type on the migration of oil between droplets in a mixed oil emulsion. Hexadecane or n-octadecane (20 wt%) was emulsified (d(32) = 0.33 +/- 0.02 mum) in 1 or 4 wt% sodium caseinate or Tween 20 solution. The freezing points of the emulsified oils were measured by differential scanning calorimetry and used to track the changing composition of the lipid droplets present. When separately prepared hexadecane and octadecane emulsions were mixed, two separate crystallization events were observed, corresponding to the two populations of oil droplets in the mixed emulsion. As the oils diffused between droplets and mixed, the crystallization temperatures of the two populations approached one another. When freshly mixed emulsions were re-homogenized together, there was an instantaneous exchange of oil between the droplets, which was greater for the Tween-stabilized than for the caseinate-stabilized emulsions. This effect increased with the number of additional passes through the homogenizer valve. (C) 2003 Elsevier Ltd. All rights reserved.