Abstract
The combinative effects of both longitudinal cut (Lc) and transverse cut (Tc), and hot air, vacuum, freeze and catalytic infrared drying (HD, VD, FD and CID) techniques on the physicochemical properties of dried ginger was studied. The physicochemical properties determined were shrinkage, hardness, rehydration rate, color, gingerol content, total phenols and flavonoids contents (TPC and TFC), antioxidant activity and volatile components. Results showed that the Lc reduced the drying time significantly, by 15.12-29.6%, compared with Tc; and improved the physical properties (degree of shrinkage, hardness, rehydration rate) of the dried ginger. However, there was no significant difference between them on the chemical properties of the dried ginger. Among the four drying techniques, CID showed the shortest drying time (1.42-1.84 h) and retained the bioactive ingredients (gingerol content, TPC, TFC, and volatile components) better in the dried products. Overall, the study established that Lc treatment combined with CID had an excellent effect on the quality of dried ginger slices and the overall drying efficiency; and thus, were selected as the optimum treatment and drying method for drying ginger.