This study focused on the application of vacuum system to synthesize capsiate analogs. The capsiate analogs containing conjugated linoleic acid (CIA) was successfully synthesized in solvent free system via lipase-catalyzed esterification. This esterification was carried out using vanillyl alcohol and CIA as substrates, and Lipozyme RM IM from Rhizomucor miehei as a biocatalyst. The best reaction condition was a molar ratio of 1:2 (vanillyl alcohol to CIA), a reaction temperature of 50 degrees C, and a lipase loading of 10% (w/w, based on total substrates). Application of vacuum increased the yield of capsiate analog as well as the reaction rate. When the vacuum levels were between 66.7 kPa and 1.3 kPa, an equilibrium yield of 100 mol% was achieved. The maximum yield was approached after only 3 h of reaction at the vacuum levels of higher than 13.3 kPa. The content of 9c,1 1t-CIA in capsiate analog synthesized was higher than that of 10t,12c-CLA. (C) 2012 Elsevier Ltd. All rights reserved.