Transesterification in a homogeneous mixture with the volatile co-solvent dimethyl ether (DME) has been proposed as a new fatty acid methyl ester (FAME) processing technique. Ternary feed mixtures of triolein, methanol and DME form a homogeneous solution, but the product mixtures of FAME, glycerin and DME form an emulsion after transesterification. In order to obtain FAME only, the glycerin phase mush be separated out from their mixtures by a centrifuge or settler. Therefore, we investigated the de-emulsification process at different methanol compositions in the feed mixtures, either with or without DME co-solvent. The rate of de-emulsification of the product mixture increased as the methanol content in the feed mixture increased: moreover, the rate of de-emulsification with DME co-solvent was 3-5 times faster than that without DME. The rate of de-emulsification was evaluated as a function of the molar ratio of dispersed glycerin phases in the product mixture. When the molar ratio of dispersed glycerin phases increased in the product mixture, the coagulation of the dispersed glycerin phases accelerated according to the Smoluchowski model. The de-emulsification was measured by UV spectroscopy as a function of time, and the relative transmissivity measured by UV spectroscopy was fit to the simple Smoluchowski equation, and the rate of de-emulsification was considered with respect to the molar ratio of dispersed glycerin phases, as calculated from the liquid-liquid equilibrium using the universal functional activity coefficient (UNIFAC) model. (C) 2011 Elsevier B.V. All rights reserved.