comparative study of the physicochemical indices of deep fried oils used by falafel street vendors in Alexandria city

Lipid oxidation represents a key barrier in the development of new food products and processes, especially convenience items and processes required to manufacture them. Deleterious changes in foods caused by lipid oxidatuion include loss of flavour, development of off-flavours loss of colour, nutrient value and functionality, and the accumulation of compounds which may be etrmental to the health of consumers. This study evaluated the physicochemical changes that occur in blends of cottonseed and sunflower oil at controlled temperatures as control and commercial frying oils were compared as a deep fat frying media. Thirty two samples of used oils were collected randomly from fallafel street vendors representing the four different zones of Alexandria city. Oils were tested physically and chemically. Results showed a significant difference in retractive indices, acid value and iodine value in the oil used for frying fallafel patties, demonstrating that each of these methods predict degradation of the oils. However, no significant difference was observed in colour, viscosity, smoke point, peroxide value, p-anisidine and% polymers in comparison to the control blend of cottonseed and sunflower oil which may be accounted for by the dilution effect during commercial frying operations. There is a need to specify suitable limits, related to quality and health factors, to determine at what point cooking oil should be discarded

Effect of intermittent heating in the laboratory on some of the physical and chemical properties of different types of refined oils

The heating performance of refined, bleached and deodorised sunflower oil, corn oil, cottonseed and sunflower oils were assessed. The quality changes in oils during intermittemt heating at 190 +/- 5°C for 10 hours per day for 5 consecutive days were determined. The change occurring in these oils as a result of thermal and oxidative decomposition during heating were evaluated. Refractive indices, viscosity free fatty acid content, p-anisidine and% polymers of both oils increased during heating, however, peroxide value, smoke point and iodine value decreases, color of oil changed gradually to dark brown from light yellow with increased heating time. Overall, the results indicated that both oils had reached the end of its useful life after 30 hours