Comparative Analysis of the Effects of Domestic Frying and Storage on Some Selected Oil Samples from Local and Commercial Sources

Abstract

Recent studies have shown that heating oil to high temperature causes oxidative degradation of the oil, consequently producing characteristics odour, taste, colour and texture. However, this study was conducted to evaluate the stability of four different samples of edible oils. Acid value was found to be 5.22, 3.50, 0.73 and 1.29 mg KOH/g oil in fresh Melon, Bushmango, olive and Palm olein oils samples respectively. When the four oil samples were used for frying, the acid value was found to be; 6.73, 3.90, 2.24 and 2.24 mg KOH/g oil (24 hours after frying), 11.22, 7.86, 4.49 and 3.3 mg KOH/g oil (2 weeks after frying) and 19.17, 13.22, 5.82 and 4.4 mg KOH/g oil (4 weeks after frying), for melon, Bushmango, olive and palm olein oils samples respectively. Saponification values were ranged between 196.70-240.00 mg KOH/g oil in fresh oils of the samples, and between 197.80-252.33 mg KOH/g oil in the oils after using them for frying. Furthermore, Peroxide values ranged from 2.65 to 3.20 Meq/Kg in fresh oils of the samples, and from 2.71 to 24.00 Meq/Kg in frying oils were to exceed the permitted value of 20 meq/Kg for olive oil and 10 meq/Kg for other edible oils in nearly half the analyzed samples. In general, feeding on these kinds of edible oils which have high values of acidity and peroxides is very dangerous because of the destructive effects of peroxide compounds and acidity on the components of the membranes of the living cell.