INFLUENCE OF MICROWAVE AND CONVENTIONAL HEATING ON THE QUALITY OF LIPIDS IN MODEL AND FOOD SYSTEMS

Refined cottonseed.and hydrogenated palm oils were heated by two metho ds, conventionally by gas cooker (deep-fat frying) and by microwave en ergy. Butter was converted to samn and liver slices were cooked with a mixture of cottonseed oil and margarine using microwave oven and gas cooker. Quality assurance methods such as acid value, peroxide value, TBA value and total sterol content of the unheated and heated lipids u nder study were determined. The time required for butter conversion to samn or cooking liver slices by microwaves was one-half of the time r equired conventionally. Exposing the oil samples or samn processing or cooking liver slices by microwaves caused some hydrolysis to free fat ty acids and accelerated the formation of hydroperoxides and secondary oxidation products. In general, the peroxide values of lipids heated by microwaves were nearly twice as high as that produced by convention al heating. Gas-liquid chromatographic analyses of fatty acids obtaine d from the heated oils or stored samn or cooked liver slices indicated the occurrence of oxidative degradation and production of short-chain acids.