Effect of microwave output power on the kinetics of color change, physicochemical and bioactive constituent features of pre-treated carrot slices

Color change is a crucial parameter in the drying process of products like carrot slices. However, the impact of microwave output power on the kinetics of color change, physicochemical properties, and bioactive compounds of pretreated carrot (Daucus carota L) slices during drying has not been fully explored. Therefore, this study aims to determine the color change kinetics, physicochemical properties, and bioactive compounds of pretreated carrot slices during microwave drying. Blanched carrot slices (3–4 min) were dipped in potassium metabisulfite (0.25% w/w, 20 min) and then dried using a microwave dryer at different power levels (170 W, 340 W, and 510 W). The color change kinetics were assessed using Hunter L* (whiteness/darkness), a* (redness/greenness), and b* (yellowness/blueness) coordinates. Additionally, moisture content, pH, total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity, and β-carotene levels were analyzed according to established methods. The mathematical modeling of color change revealed that L*, a*, and b* values fit both zero-order and first-order kinetic models, while the total color change (ΔE) followed a zero-order kinetic model. Among the three microwave power levels, 170 W showed superior physicochemical characteristics: moisture content (5.1 %), pH (5.45±0.12), total phenolic content (153.23±1.61 g/ml), total flavonoid content (23.33±0.76 g/ml), antioxidant activity (63.90±0.78 g/ml), and β-carotene content (67.28±0.61 ppm). Therefore, it is recommended to use a pre-treated 170 W microwave output power for drying carrots and other fruits and vegetables to preserve color, nutrients, and energy.