Kinetic model of the cholesterol oxidation during heating

The formation of cholesterol oxidation products (COPs) during heating of cholesterol at 150 degrees C for up to 30 min was kinetically studied using nonlinear regression models. The various COPs were analyzed by TLC and HPLC. Results showed that the COPs concentration increased with increasing heating time, and the cholesterol loss reached 64.8% after 30 min of heating. In the early stage of oxidation, the highest rate constant (h(-1)) was observed for 7-hydroperoxycholesterol (7-OOH) formation, followed by epoxidation, dehydration, reduction, and dehydrogenation. The reactions for formation of 7-OOH (7 alpha-OOH and 7 beta-OOK) and 5,6-epoxycholesterol (5,6 alpha-EP and 5,6 beta-EP) fit the second-order, while the other reactions fit the first-order. The correlation coefficients (r(2)) for the reactions ranged from 0.79 to 0.99. The kinetic model developed in this study can be used to predict the concentration changes of COPs during the heating of cholesterol.