Characterization of Home-Made and Industrially Produced Niger Seed Oils by Fluorescence Spectroscopy

Abstract

Home-made and industrially produced Niger seed oils were characterized by a fluorescence spectrometer to analyze the impact of the industrial process on the physical and chemical properties of the oil. The excitation wavelength was varied from 350 nm–380 nm with an incremental step of 10 nm, and the slit width was kept at 5 nm. Experimental results indicated that the major components in oil samples (home-made, unrefined, and refined industrially produced) were Vitamin E, Poly-unsaturated fatty acid, and Chlorophyll. Emission spectra recorded in the range of band between 400 nm – 500 nm were related to Poly-unsaturated fatty acids; those spectra recorded in the range of band between 500 nm-550 nm with a peak around 548 nm belong to vitamins E; and the band of emission wavelength between 650 nm – 725 nm were due to Chlorophyll. It was also observed that the refined oil had a very small vitamin E peak. This could be associated with the heating process of refining, as vitamin E is heat-unstable. Moreover, the emergence of new peaks in the spectra of the refined oil between 400 nm – 450 nm was due to fat-soluble vitamins and lipids that emerge as a result of oxidative reaction during the heating process. Moreover, an increase in excitation wavelength also resulted in a blue shift of the emission spectra. This was because of the presence of more than one fluorophore (luminophore) in the molecule. The calculated quantum yield of the fluorescence of the sample/un-purified was 0.01042, which is a 10% reduction compared to the purified oil. An increase in pH values also resulted in a decrease in fluorescence intensity and vice-versa.