Background. It is widely accepted that green vegetables are a rich source of nutrients, especially among populations that consume plant-based diets. A diet based on green vegetables can help to prevent cognitive decline, as well as other health problems. In this study, five green vegetables commonly consumed in Kosovo were subjected to an analysis of the influence of heat treatment methods such as boiling, frying and microwave cooking on the mineral content, as well as the reduction of toxic metals in their composition.
Results and conclusions. In general, cooked vegetables lose a lot of their nutrients such as potassium (K), sodium (Na), phosphorus (P), magnesium (Mg), zinc (Zn), copper (Cu) and manganese (Mn) compared to raw vegetables. Conversely, all cooked vegetables had increased levels of calcium (Ca), which ranged from 5 to 16 %, and iron (Fe) from 6 to 12 %, while the concentration of Cu, Pb and Ni was lower in all the vegetables examined. The concentration of Cr was higher in all green vegetables (uncooked); the sample of spinach had higher levels of Zn, Fe, Mn and Cd than the maximum allowed limit suggested by FAO/WHO. This study showed that microwave cooking was the most effective method for preserving the nutritional values (minerals) and reducing the toxic elements of vegetables, while boiling had an effect on reducing nutritional minerals. On the other hand, the frying of the vegetables examined had an effect on increasing the mineral composition and moderate reduction of toxic elements. Therefore, the food processing method in general has a pronounced effect on the composition of nutritional minerals, while a minimal effect on the reduction of toxic metals content in the green vegetables analyzed.