Résumé
The kinetics of trans-beta-carotene and trans-lutein degradation were individually investigated in palm olein and Vegetaline (R), at four temperatures ranging from 120 to 180 degrees C. HPLC-DAD analysis was carried out to monitor trans and cis carotenoid variations over the heating time at each temperature. In both oils, initial trans-beta-carotene and trans-lutein degradation rates increased with temperature. Trans-lutein was found to degrade at a slower rate than trans-beta-carotene, suggesting a higher thermal resistance. The isomers identified were 13-cis- and 9-cis-beta-carotene, and 13-cis-, 9-cis-, 13'-cis-, and 9'-cis-lutein. In spite of the higher number of lutein cis isomers, their total amount was lower than that of beta-carotene cis isomers. Trans and cis carotenoids were involved in degradation reactions at rates that increased with temperature. All degradation rates were generally found to be lower in Vegetaline (R) than in palm olein. These results were explained by the initial composition of the two oils and especially their peroxide and vitamin E contents.