by Prof. /Dr. Mohammad E. Khosroshahi.
Abstract
UV-Vis absorption and fluorescence spectroscopy were utilized to test the quality and composition changes in extra virgin olive oil (EVOO) and canola oil (CO) as influenced by temperature. Increasing the temperature resulted in molecular structural changes in both types of oils, observed as a gradual decrease in intensity amplitudes of absorption and fluorescence signals. Significant alterations were noted at approximately 200°C, where the main spectral features of pheophytin-a, carotenoids (lutein), and vitamin E in EVOO, along with linoleic acid and oleic acid in CO, nearly disappeared. An independent experiment demonstrated that laser output varies with input under constant temperatures (e.g., room temperature), showing transmission values of ~33% and ~75% for EVOO and CO, respectively. However, heating the oils led to non-linear transmission behavior, indicating molecular optical responses to thermal changes. The effects of storage time and oil adulteration were also evaluated.
