During enzymatic reactions carried out in supercritical CO(2) (SCCO(2)) media. CO(2) can expand the liquid reactant mixture, especially lipid-type substances, due to pressure increase and dissolution of CO(2), causing viscosity reduction, and improvement of the diffusion of reactants and products. For better understanding of the transesterification reaction of canola oil and canola stearin in SCCO(2) media, the viscosity of canola oil at 40, 50, 65, and 75 degrees C and its blend with canola stearin (30 wt%) at 65 C in equilibrium with high pressure CO(2) was measured up to 12.4 MPa using a rotational rheometer equipped with a high pressure cell. The solubility of CO(2) in canola oil at 40 and 65 degrees C and its blend with canola stearin at 65 degrees C was also determined at pressures of up to 20 MPa using a high pressure view cell. The viscosity of canola oil at 40, 50, 65, and 75 degrees C and its blend with canola stearin at 65 degrees C decreased exponentially to 87.2, 84.7, 74.8, 66.2, and 74.2% of its value at atmospheric pressure, respectively, with pressure increase up to 12.4 MPa. The viscosity of the samples decreased with an increase in temperature, but the effect of temperature diminished above 10 MPa. The viscosities of CO(2)-expanded canola oil and its blend with canola stearin at 65 degrees C were similar up to 12.4 MPa. The samples exhibited shear-thickening behavior as the flow behavior index reached almost 1.2 at elevated pressures. The mass fraction of CO(2) in canola oil at 40 and 65 degrees C and its blend with canola stearin at 65 degrees C reached 24 and 21% at 20 MPa, respectively. The Grunberg and Nissan model was used to correlate the viscosity of CO(2)-expanded lipid samples. (C) 2011 Elsevier B.V. All rights reserved.