Capabilities of different cooking oils in prevention of cholesterol oxidation during heating

The potential of various cooking oils to prevent cholesterol degradation and/or oxidation, as measured by the production of 7-ketocholesterol during heating at different temperatures, was studied using a cholesterol model system. In the control group (without cooking oil), cholesterol was relatively stable, and 73 % of its initial concentration was present after 30 min of heating at 125 degrees C. Less than 30 and 10 % of cholesterol remained at 150 and 175 degrees C after 30 min, respectively, and 10 % at 200 degrees C after 10 min. In the treatment group, cholesterol mixed with corn, canola, soybean, or olive oil had significantly improved thermal stability. More than 60 and 40 % of cholesterol remained at 150 and 175 degrees C after 30 min, respectively. In the control group, 7-ketocholesterol was produced when samples were heated above 150 degrees C, and levels increased consistently during 30 min of heating. At 175 or 200 degrees C, the level of 7-ketocholesterol did not increase further after reaching the highest level after 10 min of heating. 7-Ketocholesterol is not stable above 175 degrees C, and its degradation rate could be much faster than its production at 200 degrees C. 7-Ketocholesterol was not found in samples of cholesterol mixed with corn oil or laboratory-prepared soybean and rice bran oils until the heating temperature was raised to 175 degrees C for 20 min. The levels of 7-ketocholesterol in those treatment groups were greater than that in the control group at 175 degrees C for 30 min. These oils may increase the thermal stability of 7-ketocholesterol and retard its degradation rate.