Microwave Heating of Sunflower Oil at Frying Temperatures: Effect of Power Levels on Physicochemical Properties

Abstract

Degradation of sunflower oil subjected to simulated frying conditions was evaluated during microwave heating at different power levels (360W, 600W and 900W) and during heating in deep-fat fryer. Discontinuous heating was performed by heating at 180 degrees C for 3 minutes and cooling for 15 minutes. This cycle was repeated for 15 times a day, for five consecutive days. Similar free fatty acid (0.28-0.31% oleic acid), K-232 (37.11-40.28) and peroxide values (10.35-11.09 meq O-2/kg) were obtained at all microwave power levels while significantly higher total polar material (57.5%), viscosity (119.4 cp), refractive index (1.4774), redness (4.2) and yellowness (70.0) values were detected at the lowest power level at the end of heating period. Microwave heating resulted in higher values of investigated parameters relative to the conventional method throughout heating and lower values of linoleic acid content at the end of heating period. Lowest power level caused the highest reduction in the level of polyunsaturated fatty acids.

Practical ApplicationsThese results show that power level is an important factor in terms of oil degradation during repetitive microwave heating. Microwave frying method can be proposed as a new way of improving the quality of fried foods considering various studies in literature. This study is quite helpful while establishing microwave frying parameters for obtaining a reduction in the level of frying oil degradation and consequently a rise in the quality of fried products.