Comparative evaluation of tray and microwave drying of black carrot (Daucus carota L.): Effects on physicochemical, phytochemical and techno-functional properties

Abstract

Drying is the most used post-harvest processing unit operation which has significant effect on the quality of ultimate produce. The current study investigated the impact of different drying techniques (microwave drying-MD at various power levels 360 W, 540W and 720W and tray drying-TD at 65 °C) on the physicochemical, functional and bioactive parameter of black carrot (BC). The retention of bioactive parameters and total antioxidant activity (DPPH, FRAP and ABTS) followed the trend of MD360>MD540>MD720>TD. In MD360, there was better retention of total phenolics (604.07 ± 1.44mgGAE/100g), total flavonoid (150.67 ± 1.47 mgQE/100g), total ascorbic acid (6.26 ± 1.75 mg/100g), total anthocyanin (19.00 ± 0.18 mg/100g), DPPH (82.91 ± 1.50 %), FRAP (8.72 ± 0.25mgTE/100g DW) and ABTS (332.66 ± 1.48 TE/100g DW). This might be due to reduced drying time in microwave drying which minimise the exposure of phytochemicals to heat and thereby reduce their degradation. However, during TD longer, the exposure time resulted in the reduction of most of the heat liable compounds present in the BC powder. Validation through Fourier-transform infrared spectroscopy as well confirmed the highest preservation of phytochemical compounds in BC powder at MD360. The results revealed that the application of MD for BC yielded superior physicochemical and functional attributes in contrast to TD.