Effects of pretreatments and drying temperatures on drying characteristics, antioxidant properties and color of ginger slice

Abstract

To reduce the adverse eff ects of hot air drying, ginger slices were pretreated prior to drying. The eff ects of 2 pretreatment methods (blanching versus dipping in 0.1% ascorbic acid solution) and drying temperatures (60, 70 and 80 °C) on the drying characteristics and the qualities of the dried ginger slices in terms of total phenolic content (TPC), antioxidant activities (DPPH and ABTS methods) and color were investigated. It was noted that the moisture content for both un-pretreated and pretreated samples decreased more rapidly when drying was performed at higher drying temperatures. However, the drying time of un-pretreated and pretreated samples was not significantly diff erent. The TPC and antioxidant activities of the ginger slices increased markedly after drying. The increase in these values was higher for pretreated samples. The dried ascorbic acid solution dipped sample exhibited the highest values of TPC and antioxidant activity. Moreover, the total color diff erence of the ascorbic acid solution dipped ginger was slightly lower than the total color diff erence of the un-pretreated ginger. However, the tested drying temperatures, ranging from 60 to 80 °C, did not aff ect the final TPC, antioxidant activities, and color of the ginger samples.