Moisture Removal of Katuwelbatu Fruit (Solonum virginianum L.) by Heat Pump Drying with Different Temperature Treatments

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.