studied the transesterification process of beef tallow with methanol. Because the solubility of methanol in beef tallow was 19% w/w at 100°C (Ma et al., 1998b), mixing was essential to disperse the methanol in beef tallow in order to start the reaction. When the sodium hydroxide and methanol solution were added to the melted beef tallow in the reactor while stirring, the stirring time was insignificant (Ma et al., 1999). Reaction time was the controlling factor in determining the yield of beef tallow esters. They also pointed out that once the two phases were mixed and the reaction was started, stirring was no longer needed. The distribution of unreacted methanol between the beef tallow ester phase and the glycerol phase was studied to determine a efficient way of downstream operation (Ma et al., 1998b). After the reaction was finished, there was 60% w/w of unreacted methanol in the beef tallow ester phase and 40% w/w in the glycerol phase. The optimum operation sequence was to recover the unreacted methanol using vacuum distillation after transesterification, separation of ester and glycerol phases and then purification of beef tallow methyl esters.