Investigation of dried medlar fruit in terms of drying kinetics and quality parameters using natural, microwave, convective and combined microwave-convective drying methods

Medlar fruit (Mespilus germenica) was dried by the natural drying at 25 ºC, convective drying at 40, 50, 60 ºC, microwave drying at 200, 400, 600 W and combined microwave-convective drying at 200 W-40 ºC, 200 W-50 ºC, 200 W-60 ºC, 400 W-40 ºC, 400 W-50 ºC, 400 W-60 ºC, 600 W-40 ºC, 600 W-50 ºC, and 600 W-60 ºC. The moisture content of fruits, whose mass is 75.00 g, was reduced from %74.07 ± 0.04 to %11.75 ± 0.07. While the shortest drying period was measured in the combined microwave-convective drying method at 600 W-60 ºC with 17 min, the longest method was determined in the natural drying method with 22500 min. The drying data were modeled with 22 different thin-layer drying models, Page equation for natural drying, Weibull equation for 40 and 60 ºC, Jena Das equation for 600 W, 400 W-40 ºC, 400 W-60 ºC, 600 W-50 ºC, and Logistic equation for 600 W-60 ºC were determined as the most suitable thin layer drying models. In all other drying methods, the Alibas equation is the model in which the best estimates are obtained. The drying method closest to the color parameters of the fresh product was measured in combined microwave-convective drying at 600 W-50 ºC and 400 W-40 ºC. On the other hand, natural and convective drying methods caused great losses in color parameters. The protein content closest to the raw material was measured in microwave drying at 400 W. In the study, the closest phosphorus, potassium, sodium, and copper contents to the fresh sample were determined at 600 W-60 °C. While manganese and magnesium content was at the maximum level at 400 W-40°C, zinc was preserved at the highest level at 600 W-40 °C. However, the calcium and iron contents closest to the fresh product were obtained at 60 ºC and 200 W, respectively. While the total extractable phenolic components closest to the fresh product were measured at 600 W-60 °C, the total hydrolyzable and bioaccessible phenolic components were measured at the highest 60 °C. The percentage of bioaccessibility of the total phenolic components of the medlar was analyzed in the highest natural drying. ABTS, CUPRAC, and DPPH methods were used to determine the total antioxidant capacity. The highest antioxidant capacity was measured for ABTS in natural drying, for DPPH at 200 W-50 °C, and for CUPRAC at 400 W-60 °C. The DPPH method, in which the highest values were measured, was chosen as the most appropriate antioxidant capacity determination method.