AbstractBACKGROUNDHigh oleic sunflower oil (HOSO) and a fatty acid (FA) mixture were inter‐esterified in a solvent‐free system catalysed by Lipozyme RM IM to produce a cocoa butter equivalent (CBE). The effects of reaction conditions on the percentage of saturate–oleoyl–saturate (SOS) and saturate–saturate–oleoyl (SSO) triacylglycerols (TAGs) were studied. The process was further optimised by response surface methodology. A five‐factor response surface design was used to investigate the influences of the five major factors and their mutual relationships. The five factors were substrate ratio (A, FA/HOSO, mol mol−1), enzyme load (B, wt% based on substrates), water content (C, wt% based on substrates), reaction temperature (D,°C) and reaction time (E, in hours) varying at three levels together with two star point levels.RESULTSThe highest yield (59.1% SOS) and lowest acyl migration (2.9% SSO) was obtained at 10% enzyme load, 1% water content, 1:7 substrate mole ratio, 65°C reaction temperature and 6 h reaction time. All the investigated factors except substrate ratio had significant effect on acyl migration.CONCLUSIONThe quadratic response models sufficiently described the acidolysis reaction. All parameters had significant effect on the percentage of SOS TAGs. Based on the models, the reaction was optimised to obtain a maximum yield of SOS TAGs. © 2013 Society of Chemical Industry