TITLE:
Effect of Temperature on Optical Properties of Vegetable Oils Using UV-Vis and Laser Fluorescence Spectroscopy
AUTHORS:
Mohammad E. Khosroshahi
KEYWORDS:
Extra Virgin Oil, Canola, Temperature, Optical Properties, UV-Vis Absorption, Fluorescence Spectroscopy, Laser
JOURNAL NAME:
Optics and Photonics Journal,
Vol.8 No.7,
July
23,
2018
ABSTRACT: UV-Vis absorption and fluorescence spectroscopy are used to test the quality and changes in the composition of extra virgin olive oil (EVOO) and canola oil (CO) with temperature. The increase of temperature caused a change in the molecular structures of both types of oils seen as a gradual decrease of intensity amplitudes of absorption and fluorescence signals. A significant alteration occurred at ≈200°C where almost the main spectra of pheophytin-a, b, carotenoids, lutein and vitamin E in EVOO and linoleic acid and oleic acid in CO disappeared. An independent experiment showed the output of laser changes linearly with the input in oil at constant temperature (i.e., room temperature) where the transmission values of ≈33% and ≈75% are determined for EVOO and CO respectively. However, the transmission through a heated oil exhibited a non-linear behaviour which indicates the molecular optical response to thermal changes. The effect of storage time and adulteration of oils were also evaluated.