Detection and Determination of Indicative products

Abstract

Deep-fat frying at 180◦C or above is one of the fastest, oldest and simplest methods used for food cooking. It involved heating an edible oil or fat and uses the hot oil to cook food. The refinedsunflower, groundnut oils and extracted moringa oleifera seedoil were each heated for six hours on one day and 36 hours on six days, at 175±5°C of frying .The oils were used to fry potato chips by taking the oil samples (2L) in the fryer for 36 hours and 1½ L for 6hours of frying. The purpose of the study was to detect and determine quantitative indicating products of free radical reactions of multiple frying using vegetable oils. moringa oleifera seed oil in deep-frying was evaluated by comparing its frying stability and physiochemical properties with those of conventional frying oils of refined sunflower and groundnut. Standard methods, changes in color, viscosity (pa.s) or kg/(m.s), refractive index(RI), free fatty acids (FFA), peroxide value (PV), conjugated dienes and trienes for the determination of used frying oil deterioration. Fourier transform-infrared (FTIR) and Gas Chromatography (GC) spectrometry was used for the analysis of fatty acids methyl ester. The statistical analysis of the results of the physicochemical properties of the frying oils shown that they were highly significantly (P < 0.00) influenced by the type and concentration of the components of the oils. During the frying process the sunflower and groundnut refined oils generally exhibited lower chemical stability than that of moringa oleifera oil. Oxidation level of fats and oils can be measured directly by the detecting the formation of radicals. Therefor thefree radicals formed eventually terminate at the final products such asaldehydes, ketones, acids, alcohols and hydrocarbons respectively. Fourier transform-infrared (FTIR) spectra of the oils how bands at 3300 cm-1_ 3600 cm-1, and1450cm-1 indicating formation of alcohols and hydrocarbons, respectively. The appearance of additional bands at about 1748.25 cm-1 ester C = O stretching indicates the formation of aldehydes, ketones, or acids. In this study it was found that, the levels of conjugated dienes throughout the frying period are lowest in moringa oleifera oil followed by that of Groundnut, and then in sunflower oil. This is due to the fact that sunflower oil, contained high percentages of polyunsaturated acids (linoleic and linolenic), have accumulated more conjugated dienes and trienes. In contrast, Moringa oleifera oil and Groundnut oil contain high percentages of monounsaturated acids, 98.212% and 89.292% respectively. It was found that sunflower oil contained high percentages of polyunsaturated acids 76.951%; whereas moringa oleifera and Groundnut oils those contained, 1.33% and 3.974%, respectively, this was indicated by gas_liquid chromatography of the methyl esters of fatty acids during deep_ fat frying. The increase in saturated fatty acid content is very high for 36h than 6h and so a decrease in polyunsaturated acid content as frying time increased. Thus, the ratio of polyunsaturated to saturated fatty acids (P/S) is considered to be a major factor affecting oil oxidation. The presence of a high content of polyunsaturated fatty acids increases the susceptibility of oil to oxidation. High frying temperature, the number of frying, the amount of free fatty acids, polyvalent metals, and unsaturated fatty acids of oil lessening the oxidative stability and flavor nature of frying oil. In any case, repeated utilization of these oils produces undesirable constituents that may cause health hazards.