Abstract: This research is to study the performance of heat
pump dryer for drying of kaffir lime leaves under different media and
to compare the color values and essential oil content of final products
after drying. In the experiments, kaffir lime leaves were dried in the
closed-loop system at drying temperatures of 40, 50 and 60 oC. The
drying media used in this study were hot air, CO2 and N2 gases. The
velocity of drying media in the drying chamber was 0.4 m/s with
bypass ratio of 30%. The initial moisture content of kaffir lime leaves
was approximately 180-190 % d.b. It was dried until down to a final
moisture content of 10% d.b. From the experiments, the results
showed that drying rate, the coefficient of performance (COP) and
specific energy consumption (SEC) depended on drying temperature.
While drying media did not affect on drying rate. The time for kaffir
lime leaves drying at 40, 50 and 60 oC was 10, 5 and 3 hours,
respectively. The performance of the heat pump system decreased
with drying temperature in the range of 2.20-3.51. In the aspect of
final product color, the greenness and overall color had a great
change under drying temperature at 60 oC rather than drying at 40
and 50 oC. When compared among drying media, the greenness and
overall color of product dried with hot air at 60 oC had a great change
rather than dried with CO2 and N2.
Abstract: The peel of dragon fruit is a byproduct left over after consuming. Normally, the use of plants as antioxidant source must be dried before further process. Therefore, the aim of this study is interesting to dry the peel by heat pump dryer (45 ºC) and fluidized bed dryer (110 º C) compared with the sun drying method. The sample with initial moisture content of about 85-91% wet basis was dried down to about 10% wet basis where it took 620 and 25 min for heat pump dryer and fluidized bed dryer, respectively. However, the sun drying took about 900 min to dry the peel. After that, sample was evaluated antioxidant activity, -carotene and betalains contents. The results found that the antioxidant activity and betalains contents of dried peel obtained from heat pump and fluidized bed dryings were significantly higher than that sun drying (p 0.05). Moreover, the drying by heat pump provided the highest -carotene content.