Drying Characteristics of Fresh Persimmons: Impacts on Color and Energy Consumption

Persimmon (Diospyros kaki) constitutes a notable fruit in Türkiye. The fruit is consumed in its fresh state during specific periods of the year, which renders it of significant importance in the context of product preservation. Drying is the most commonly used method for preserving products. Drying requires significant energy consumption. The drying time and method employed have a direct impact on both energy consumption and product quality. Persimmon is a nutrient-dense fruit that needs to be dried for extended shelf life. This study investigated the drying behavior of persimmon slices having an initial moisture content of approximately %73.8 wet basis in a microwave oven. Moisture diffusion, shrinkage, color change and rehydration properties were investigated as a function of microwave power and slice thickness. Samples were prepared at two different thicknesses (5 mm and 9 mm) and tested at three microwave power levels (350 W, 460 W and 600 W). Curve fitting tools in the Matlab programmer were used to model the variation in moisture content over time. The study utilised six models: Lewis, Page, Henderson and Pabis, Logarithmic, Midilli, Wang and Singh. The logarithmic model has been demonstrated to provide the most accurate description of persimmon drying kinetics. The dried products' quality was evaluated through various parameters, including color metrics (L*, a*, b*), color difference (ΔE), browning index (BI), chroma, and hue angle, along with rehydration and shrinkage ratios. The effective diffusion coefficients of persimmon were found to range from 2.27 × 10-10 to 9.08 × 10-10 m²/s. Specific energy consumption ranged from 2.21 to 3.028 kWh/kg. The lowest ΔE value was observed in the samples dried at 460 W, suggesting that the highest power (460 W) effectively preserved the natural color of fresh persimmon and minimized browning reactions during the drying process. Results indicated that the applied microwave energy significantly influenced the drying process of the persimmon and the observed changes.