impacts of different drying methods on the ascorbic acid content of peach slices

this study analysed the convective (60 and 80° c), microwave (180, 270 and 360 w) and freeze drying methods in terms of their effects on drying rate and ascorbic acid content of peach slices with 0.5±0.1 cm thichness. drying was carried out from the initial moisture content of 5.684±0.05 kg water/kg dry matter to 0.175 kg water/kg dry matter. the weight of samples was recorded online by a digital balance and with 1 min intervals. the moisture ratio (mr) curves were plotted and showed that increasing in drying temperature and/or power output, reduces drying time. microwave drying at 360 w was the fastest method. ascorbic acid (asa) content was determined using high performance liquid chromatography (hplc). the residual ratio of asa content was 0.66 - 0.98. microwave dried samples at 360 w particularly had the lowest residual asa content ratio and freeze drying method yielded the closest value of asa content to fresh sample when compared to the other methods.