Abstract:
This work aimed at evaluating the thin layer drying
behaviour of amaranth grains (Amaranthus cruentus) and
comparing the quality of the grains dried under solar-energy
tent dryer systems and the open sun. The dryers were covered
with clear, yellow and nectarine diffused polyvinyl chloride
(PVC) materials of 200 micron thickness whose transmissivities
were 90%, 85% and 82%, respectively. The ambient
temperature and relative humidity ranged from 23.3～33.5oC
and from 24% ～ 46%, respectively, while the inside
temperature and relative humidity in the solar dryers ranged
from 30.4～50.7oC and from 15%～44%, respectively. Fresh
amaranth grains with an initial moisture content ranging from
66.7% ～ 68.8% dry basis (d.b) were dried under both
conditions for 8 hours to an equilibrium moisture content of
about 7% d.b. The quality attributes assessed were colour,
hardness and crude protein content. The findings showed no
significant effect of colour of cover material on the grain quality.
The study demonstrates that natural convection solar tent
dryers covered with PVC materials enhance the thin layer
drying rate of amaranth grains without significantly affecting
their quality.
