Thermal Stability of Chlorophyll Pigments in Virgin Olive Oil

The aim of the present study was to determine the changes in the chlorophyll content and the K-232 and K-270 specific extinction coefficient values in virgin olive oil (VOO) subjected to high temperatures for 24 h. VOO, was obtained from Kahramanmaras city, Turkey, and subjected to 150, 160, 170, 180. 190 and 200 degrees C for 2, 4, 6, 8, 10, 12 and 24 h, and the chlorophyll content and the K-232 and K-270 specific extinction coefficient values were determined. The chlorophyll content of VOO decreased significantly as the treatment temperature and the extent of heat treatment increased (P< 0.05) Especially, the temperature above 180 degrees C, the chlorophyll content decreased below 3% after 24 h. The K-232 and K-270 specific extinction coefficient values of VOO increased significantly with increasing the treatment temperature and time (P< 0.05). The values of K-232 and K-270 specific extinction coefficients reached to 9.12 and 5.28 (1%, 1 cm), respectively, at 200 degrees C after 24 h. However, the rates of the increase in these values did not change with respect to different temperature and time. A significant inverse relationship was found between the chlorophyll content and the K-232 and K-270 specific extinction coefficient values (P< 0.05). This study showed that chlorophyll, as one of the major quality criteria for olive oils, is heat-liable, and decomposes at high temperatures and long treatment times. In addition, increases in the conjugated diene and triene contents of VOO indicate the accelerated oxidation reactions at high temperatures; therefore VOO is no longer classified as "virgin olive oil" according to the official standards.