Effect of Refining and Thermal Processes on Olive Oil Properties

Olive cultivars Bladi and Arbequina were collected and their oil was extracted (cold press). Oil was refined under bleaching and deodorization conditions for 30 minutes at 5550°C and their property was compared with the virgin olive oil. Virgin and refined oils of the cultivars were processed by fryer heating at 180°C (intervals of 0, 1, 2, 4, and 8 hours) and indexes of fatty acid, free fatty acid, peroxide, thiobarbituric acid, polar compounds, conjugated dienes and trienes, Rancimat, color, total polyphenol, tocopherol, chlorophyll and carotenoid were compared. Results showed that these oils mainly contained oleic (48.6960.18%), palmitic (18.3127.02%), linoleic (7.5418.58%), palmitoleic (3.93.08%), stearic (1.782.53%), and linoleic acids (1.870.22%). According to the results, it was recommended to refine virgin olive oil by mild bleaching and deodorization to save bioactive compounds. Due to the heating condition, the relative amounts of unsaturated fatty acids (22.3750.6%), polyphenols, tocopherols, chlorophyll, carotenoid and oxidative stability decreased and the relative amounts of saturated fatty acids (14.217.1%), acidity, peroxide, conjugated dienes and trienes, polar compounds, and thiobarbituric acid increased significantly, but the colorant initially decreased and then increased (P 0.05). Due to polar compounds, for frying process, mild refined oil was better than extra virgin oil.