The quality and infrared determination of trans-fatty acid contents in some edible vegetable oils

Abstract

The analysis of some edible vegetable oils available in the Cape Coast metropolis in Ghana has been carried out by physical and chemical methods quality determination and comparative analysis. The parameters investigated were the specific gravity, refractive index, iodine value, saponification value, acid value, free fatty acid content, percentage impurity. The specific gravities of the oils ranged from 0.9096 to 0.9984 whilst the refractive indexes were from 1.445 to 1.507. The saponification value ranged from 187 for ‘Werewere to 244 for coconut while the iodine values varied from 9.5 for coconut to 135 for safflower. The other parameters were from 0.187 for soyabean oil to 6.89 for ‘Werewere oil for the acid values and between 0 to 6% for the free fatty acid of the oil samples. The trans- fatty acid contents of the oils were also investigated by Fourier Transform Infrared (FTIR) spectroscopic method by the determination of the transmittance ratios of the absorbances at 966 cm -1 in the infrared spectra of the oils. The trans-fatty acid contents ranged from minimum of 0% for olive oil to a maximum of 6% in Werewere oil. The results indicated that the oils were of good quality and that the amounts of trans-fatty acid were not appreciably high to pose any health risk to consumers