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) andfreeze drying methods in terms of their effects on drying rate and ascorbic acid content of peach sliceswith 0.5 cm thichness. Drying was carried out from the initial moisture content of 5.684 0.05 kgwater/kg dry matter to 0.175 kg water/kg dry matter. The weight of samples was recorded online by adigital balance and with 1 min intervals. The moisture ratio (MR) curves were plotted and showed thatincreasing in drying temperature and/or power output, reduces drying time. Microwave drying at 360W was the fastest method. Ascorbic acid (AsA) content was determined using High PerformanceLiquid Chromatography (HPLC). The residual ratio of AsA content was 0.66 - 0.98. Microwave driedsamples at 360 W particularly had the lowest residual AsA content ratio and Freeze drying methodyielded the closest value of AsA content to fresh sample when compared to the other methods.

Keywords:

Peach , Ascorbic acid , Freeze drying , Microwave , Hot air drying