Moisture diffusivity and activation energy
The effective moisture diffusivity was calculated
by using the method of slopes. According to the
experimental data obtained at various microwave
output power levels, the logarithm of moisture ratio
values, ln(MR), were plotted against drying time (t).
The linearity of the relationship between ln(MR)
and drying time is illustrated in Figure 5 for various
output powers (with R2 more than 0.95 for all the
levels). The effective moisture diffusivity values
(Deff) for various microwave output powers were
calculated and presented in Table 4. The range of
moisture diffusivities varied from 5.35E-08 to 1.99E-
07 m2/min. No literature was found out related to the
effective moisture diffusivity for Pandanus leaves
undergoing any drying treatment. However, various
research workers have worked on other leaves.
Though similar trends were observed, the range of
effective moisture diffusivity of Pandanus leaves
undergoing microwave drying were higher than
the values obtained by Akpinar (2006) for different
aromatic plants. This may be due to the lower drying
times required under microwave treatment.
The values of k versus m/P accurately fit to the
exponential model as evident from Figure 6 with
coefficient of determination (R2) of 0.981. Then k0
was estimated as 0.275 and Ea was determined to
be 13.6 W/g and found similar as 12.2839 W/g and
11.0492 W/g, respectively (Dadali et al., 2007).