Abstract

M. A. Moharam and L. M. Abbas*

Fourier transform infrared spectroscopy (FTIR) was used for the structural characterization of vegetable oils (olive, cotton, corn and sunflower oils) following the induced changes in their structure brought about by microwave heating. The vegetable oils samples were microwave heated at 2 powers (450 and 630 W) for different times ranging from 2 - 28 min. The investigation of the FTIR spectra of the treated oils revealed that the microwave heating of oils for different periods of time at 450 and 630 W caused significant changes in the intensities of their absorption bands and produced no shifts in the position of the bands. The results showed that, the microwave heating of oils produced changes in the absorbance ratios A 3006/A 2924 cm-1 (RI) , A 3006/A 2854 cm-1 (RII) and A 3006/A 1746 cm-1 (RIII) which were taken as a measure for the degree of unsaturation. It was found that the changes depended on the applied power, the time of heating and the type of oils. Microwave heating of oils at 630 W for any given time produced an initial decrease in the ratios RI, RII and RIII. This decrease was attributed to the reduction in 18:2 and 18:3 fatty acids content due to the oxidation.