ISSN 2360-7971
Abstract
Accepted 2nd December, 2016.
Five different oils were selected for frying process, thermal behaviour (temperature changes). The data obtained indicates that after one minute of frying time ,the temperature decreased from 180ºc to 140, 150, 160 ,140 and 140ºc for olive, ,corn, blend, sunflower and flaxseed oils respectively . The temperature continued to decrease according to the type of oil and reached the minimal the temperature at 125, 126, 135, 128, and 130ºc for same studied oils respectively. The obtained date from thermal behaviour carves showed that the calculated convection area percentages for olive ,corn, blend, flaxseed and sunflower oils were 27.7, 40.08, 42.8, 14.6 and 37.01 % respectively meanwhile the calculated conduction area percentages for the same oils were 72.2, 59.9, 57.1, 85.3 and 62.9 respectively of total heating area. Where the greater the conduction area percentage was the greater the oil potential for frying and the better the fried food. The results from thermal behaviour carves of the five oils during frying process at 180°c after heating for one hours .showed that the initial time required reaching 180°c increased with increasing the heating time (frying cycles) . This time was stable (7, 8 ,9 minutes) for olive oil ,flaxseed and sunflower oil and did not change as compared to that recorded at zero heating time(control) and it increased to (9.5 and 14 minutes) for corn and blend oils respectively. The data obtained also revealed that the percentages of convection area increased and loss of water from 27.7, 40.0, 42.8, 14.6 and 37 after (one hours) to 33.7, 43.0, 55.8 , 33.3 and 39.0 after 2 hours of heating for olive, flaxseed, sunflower, corn and blend oil respectively . Meanwhile, the percentage of conduction area decreased from 72.2, 59.9, 57.1, 85.3 and 62.9 after frying for 1hr to 66.2,56.9,44.1,66.6 and 60.9 for the same studied oils. Eight Frying time did not change for both flaxseed and sunflower oils and was constant at 10.9 and 9 minutes while at increased to 20 minutes for corn and blend oil.
Keywords : Frying, thermal behaviour, vegetable oils