Effects of microwave and hot-air drying methods on colour, β-carotene and radical scavenging activity of apricots


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The effects of drying by microwave and convective heating at 60 and 70 °C on colour change, degradation of β-carotene and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging activity of apricots were evaluated. Microwave heating reduced significantly the drying time (up to 25%), if compared with convective one, also owing to the higher temperature reached during the last phase of the process, as monitored by infrared thermography. Colour changes of apricot surface, described with lightness and hue angle, in both drying methods followed a first-order reaction (0.927 ≤ R2 ≤ 0.996). The apricots dried by microwave were less affected by the darkening phenomena. The evolution of β-carotene in fresh apricots (61.2 ± 5.6 mg kg−1 d.w.) during the drying highlighted a wider decrease (about 50%) when microwave heating was employed for both the temperatures used. Radical scavenging activity increased (P < 0.05) in all dried samples except for hot-air dried apricots at 60 °C.