The aim of this research is to evaluate the quality of oils used in the frying process in commercial restaurants. Oil samples were collected from deep fryers in two commercial restaurants in the area of Bosnia and Herzegovina. One of the restaurants used partially hydrogenated oil and the other sunflower oil. The analysis samples were collected during one 12-hour shift, in two-hour intervals. Physico - chemical parameters, changes in fatty acid composition during frying, and the presence of metals were analyzed.
The research results have shown that there is a statistically significant difference (p < 0.05) between all analyzed parameters, for both types of oils. During frying, the composition of fatty acids for both oils changes significantly. Total oxidation value for partially hydrogenated oil was increased from 2.165 to 55.983 mg/kg oil, and for sunflower oil from 15.332 to 153.888 mg/kg. During frying, there is an increase in the metal content (p < 0.05) in the tested oils.