Quality changes of sunflower and palm oil during deep fat frying

Frying is a widely used method of cooking in the institutional or industrial preparation of food. Deep fat frying is accomplished by the formation of many compounds that are mainly developed during the prolonged use of oil. Some of these compounds are undesirable. As food prepared in this manner contains substantial amounts of fat (some as much as 40%) there is a need to define the alteration level at which the fats or oils must be discarded. Oil origin, product being fried and duration of frying influence stability and sensory properties of frying oils. In this study the changes of oil quality as well as fatty acid composition of sunflower and palm oil were investigated. The oils were studied during intermittent potato strips frying at 185 degreesC for 8h per day for 4 consecutive days, without replenishment of the used oil with fresh oil. Oil samples were collected from the fryer after 0,8 16 and 24 hours of frying. The indices used for the assessment of changes in quality of the oils were fatty acid composition, peroxide value, anisidine value, fraction of free fatty acid and polar components. The results obtained have shown that palm oil was superior to sunflower oil in frying performance in resistance to termooxidation.