ABSTRACT
The experiment was carried out and
three osmotic solutions were prepared, “hypertonic solution 60%
concentrated, hypotonic solution 40% concentrated and isotonic solution
50% concentrated” and oven drying was also carried in the course of the
experiment, the effect of sodium chloride (osmotic agent) concentration,
temperature and immersion time on overall mass transfer coefficient,
effective diffusivity, drying rate weight loss and shrinkage ratio on
oven drying and osmotic dehydration of Pumpkin and bitter leaf. Results
showed that both pumpkin and bitter leaf had a highest mass transfer
coefficient in oven drying at highest temperature of 80oC, for pumpkin leaf 0.149(m/min), bitter leaf was 0.149(m/min), the results were also obtain for osmotic dehydration at 80Oc
at highest concentration (Hypertonic solution) had the highest mass
transfer coefficient, for pumpkin leaf was 0.015(m/min) for bitter leaf
was obtained to 0.032(m/min). For osmotic dehydration, both samples
weight loss percent (WL%) for hypertonic solution at 800C for
90mins had the highest weight loss percent, but the shrinkage ratio
decrease with increase in time.The mass transfer during oven drying of
pumpkin and bitter leaf was described using Fickian equation of
diffusion with drying taking place in the falling rate period, the
effective moisture diffusivity value showed temperature dependence on
both samples. Effective diffusivity values were also determined for oven
drying at different temperature, and the values increases as the
temperature increases, for pumpkin and bitter leaf at 600C, 700C and 800C, the effective diffusivities were 1.0E-09, 1.87106E-09 and 2.1843E-09m2/min and 8.52966E-10, 1.00015E-9 and 2.45308E-08m2/min.