The total drying times of the syrup decreased from 480 to
315 minutes at temperatures that ranged from 30 to 80 °C
while drying times for zvambwa decreased from 375 to
255 minutes at the same temperature range (Figs. 3 and 4).
The observed differences in the drying times for the syrup and
zvambwa may be attributed to differences in the initial moisture
content of the two products and differences in molecular
arrangements in the matrices of the products. The initial
moisture contents of the syrup and zvambwa measured on a
dry weight basis were 25.7±0.6 % and 19.8±3.0 % respectively.
As shown in Figs. 3 and 4, the moisture ratios of the
syrup and zvambwa dried at each temperature decreased with
time. The findings are consistent with results obtained for thin
layer drying of pumpkin slices (Doymaz 2007), tomato slices
(Abano et al. 2011) and Uryani plum (Sacilik et al. 2006). As
the temperature increased the drying time decreased. The
increasing temperature increased the energy of water molecules
allowing for their rapid escape from the matrix of the
products. The decrease in the moisture ratio that resulted from
loss of moisture from the syrup of Parinari curatellifolia fruit
and zvambwa indicates that the internal mass transfer is governed by diffusion similar to the case for thin layer drying
in yams (Koua et al. 2013; Falade et al. 2007). As illustrated in
Figs. 5 and 6, the drying rates of the syrup and zvambwa
decreased with time, until theywere almost constant. At all the
temperatures considered the drying rates were falling. The
drying rates for the products increased with increase in drying
temperature with the highest drying rates observed at 80 °C.