2. Industrial Process

Interesterification results when fat is heated at relatively high temperatures (less than 200ºC) for a considerably long period. Nevertheless, catalysts are frequently used that permit a shorter period (30 min.) for the completion of the reaction at temperatures as low as 50ºC. Alkali metals and alkali metal alkylates are effective low-temperature catalysts, sodium methoxide ("methylate") being the most commonly used one. Approximately 0.1% catalyst is required. Higher concentrations may cause excessive losses of oil resulting from the formation of soap and methyl esters.

The oil to be esterified must be extremely dry and low in free fatty acids, peroxides and any other material that may react with sodium methoxide. A few minutes after the catalyst is added, the oil acquires a reddish brown color due to the formation of a complex between the sodium and the glycerides. This complex is thought to be the true catalyst. After esterification, the catalyst is inactivated through the addition of water or acid, and removed.