EFFECT OF DIFFERENT DRYING METHODS ON THE PHYSICAL PROPERTIES AND QUALITY OF SOME FRUIT PEELS

Fruit peel represents approximately 30-40 g/100g of the fresh fruit mass and could be used to develop value-added products rather than causing pollution of the environment. Fruit peels of orange, lemon, pomegranate and grapefruit were dried using two different drying methods (oven and microwave) under different fruit peels masses of 50, 100, 150 and 200g in order to study the drying behavior in terms of specific energy, drying efficiency and product quality. Mathematical models of the oven and microwave dryers were investigated based on the experimental data in order to predict their performance.  The obtained data revealed that the use of a microwave was accompanied with higher drying rates of fruit peels, higher drying efficiency and lower specific energy compared with electric oven. The best product quality was achieved in the case of using fruit peels of 50g in the microwave and 200g in the oven comparing with other peels masses. In oven, Newton and Henderson and Pabis models showed good agreement with orange and lemon, while Page and Modified Page (I) were the best descriptive models for pomegranate peels. Regard to the drying in microwave, Page and Modified Page (I) models showed good agreement with all fruit peels (orange, lemon, pomegranate and grapefruit).