Glycerolysis-hydrolysis reactions to produce monoacylglycerol (MAG) and diacylglycerol (DAG) used in the production of functional foods and nutraceuticals were conducted in supercritical carbon dioxide (SC-CO2) media to elucidate the reaction kinetics, provide the reaction mechanism and assess the potential catalytic agent involved. Reactions were conducted in an electrically heated, magnetically stirred autoclave at 250 degrees C, 10-30MPa, anhydrous glycerol/canola oil molar ratio of 34:1 and initial water content of 0 to 8% (whw). Reactions were also conducted in supercritical nitrogen at 250 degrees C, 10MPa, and 8% (w/w) initial water. Samples were collected as a function of time and the concentrations of MAG, DAG, free fatty acids (FFA) and triacylglycerol (TAG) were obtained using thin layer chromatography-flame ionization detection. The maximum rate of MAG formation at 20MPa was significantly higher (p <= 0.05) than that at 30MPa, but similar (p > 0.05) to that at 10MPa; a finding that has economical impact because a pressure of 10MPa can be reached without the use of a high-pressure pump. Rates of MAG formation in SC-CO2 and -N-2 media were similar (p > 0.05) thereby demonstrating that SC-CO2 does not contribute to catalysis. The maximum rate of MAG production at 10 MPa was significantly higher (p < 0.00 1) for reaction with 4% (w/w) initial water compared with anhydrous reactions and was significantly lower (p < 0.05) compared to that of reaction with 8% (w/w) initial water. Although this study was unable to identify the catalytic reagent, it did show that water played an important role. Reactions were carried out up to 14 h and equilibrium was reached at 9 h. The average equilibrium composition (mol%) obtained at 9-10 h for the reactions conducted at 10-30 MPa with 4-8% (w/w) water was 66-71% MAG, 13-15% DAG, 13-17% FFA and 0-1% TAG. A MAG concentration of > 65% is higher than that obtained in conventional glycerolysis where the concentration of MAG generally does not exceed 58%. Such findings not only demonstrate improved yields but also lead to a better understanding of the complex mechanisms of simultaneous glycerolysis-hydrolysis reactions and are critical for optimal process design targeting the MAG and DAG products. (c) 2006 Elsevier B.V. All rights reserved.