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 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