Abstract:
Katuwelbatu (Solonum virginianum L.), is a commonly found prickly herb in most of the Asia and
used as a valuable indigenous medicine. In Sri Lankan condition, Katuwelbatu (Solanum
virginianum L.), a medicinal plant mainly used for colic fever, loss of appetite and in the treat
itching, fever, cough and cold etc. Different pre-treatment methods are used to increase the
drying rate of Katuwelbatu fruits when drying using heat pumps. This research study was
focused to identify the most suitable pre-treatment condition for heat pump drying of
Katuwelbatu fruit in different temperature treatments. Hot air drying and Hot water blanching
pre-treatment method were conducted at 40°C, 60°C and 80°C (3minutes) temperature,
respectively. The experiment was conducted in completely randomized design with three
replicates. Pre-treated Katuwelbatu samples (30g) were dried in a heat pump dryer for 142.6
hours. The drying characteristics and colour variation (ΔL, Δa, Δb, and ΔE) of the katuwelbatu
fruits were analysed. Dehumidify room conditions were monitored by recording relative
humidity and temperature data by a data logger during research time period. The initial
moisture content of fresh and pre-treated fruit samples was 80 %±1 (wb). The 80°C hot water
treated sample had the lowest final moisture content of 50 %±1 (wb) while other sample had
final moisture content of 70%-75% (wb). The values of the drying constant of control, 40°C hot
water and hot air treated, 60°C hot water and hot air treated and 80°C hot water and hot air
treated were -0.0015,-0.0016,-0.0014,-0.0018,-0.0016, -0.007 and -0.0017, respectively. The
colour changes of 80°C hot water treated sample obtained more closer to the reference colour
(golden brown) value (ΔL=12.86, Δa=-2.87, Δb=10.67, ΔE=16.95) for Katuwelbatu fruit. The
statistical analyses indicated that 80°C hot water treated sample moisture content was
significantly different (P< 0.05) than that of pre-treated samples. The results suggest that the
80°C hot water treatment increases the drying rate of Katuwelbatu fruits in heat pump drying.
