Effect of maturity stage and drying on the physicochemical properties and drying kinetics of Solanum torvum fruits

This study investigated the effects of maturity stage and drying on the nutritional and antioxidant properties of Solanum torvum fruits, as well as their drying kinetics. Fruits were harvested at three maturity stages and dried at 35 °C for 48 hours. Both fresh and dried samples were analyzed for proximate composition, bioactive compounds, and antioxidant activity. Drying kinetics of fresh fruits were modeled by fitting various empirical models (Newton, Henderson and Pabis, Wang and Singh, and logarithmic models) to experimental data and evaluating their performance. Physical dimensions (length, width, thickness) varied significantly (p < 0.05) with maturity stage. Stage 1 fruits (green color) had the lowest values for physical dimensions (length, width, and thickness), while stage 3 fruits (red color) showed the highest levels of protein (11.26 g/100 g DM), lipids (13.31 g/100 g DM), carbohydrates (54.37 g/100 g DM), tannins (20.04 mg/100 g DM), and total phenolic compounds (1145.11 mg/100 g DM). Drying led to a reduction in vitamin C content, from 216.45 to 194.35 mg/100 g DM, but resulted in increased concentrations of certain nutrients like fiber and ash. The highest drying rate (0.12 g/g·min) was observed at stage 1, and the logarithmic model best fit the drying data (R² = 0.98). Overall, selecting the appropriate fruit maturity stage can optimize both drying efficiency and nutritional quality of dried S. torvum fruits.