Design and Construction the Centella asiatica (L.) Urban Leaves Dryer by an Infrared Type

Abstract

The objective of this research was to design and construct a prototype infrared dryer for
Centella asiatica (L.) Urban leaves. The study of machine operation, decreasing of moisture content and
color qualities of dried leaves by infrared dryer, were studied. The designed dryer had dimension which
its width x length x height, was 41 x 51 x 41 cm. The 500 W infrared heater source was installed at the
top of dryer and the temperature controller was installed to control the inside air temperature was
range of 40–50ºC which was suitable for drying the Asiatic leaf that the moisture content of the dried
product is less than 10% dry basis. From the study of moisture content, the optimum drying time was
3.5 hours that moisture content of the dried product was 6.92±0.24% that was according to the
community product standard. From the study of the drying efficiency of the machine at test time was
3.5 hours, found that, the efficiency of the machine was 22.47±0.73%, the specific energy consumption
was 16.36±0.53 MJ/kg and the percentage of dried product was 13.63±0.60%. In addition, the quality of
dried product was studied. aw value of the dried product was 0.33±0.02, which was less than 0.65 that
was according to the community product standard. For the color quality of the dried product, the
overall color difference from the fresh leaves (∆E) was less than other dried product. It was found that
the dried product from the infrared dryer was a brightness (L*), the green color (a*) and the yellow color
(b*) were significantly higher than the fresh leaves (P≤0.05). So, this prototype infrared dryer can apply
for the drying of the C. asiatica leaves.