Drying Characteristics of Red Chillies
Kaleemullah and Kailappan (2004) reported the equilibrium moisture for small red chillies using the static method at 25, 35 and 45oC over a range of relative humidities from 11.5 to 86.5%. The sorption capacity of chillies decreased with an increase in temperature at constant relative humidity. The sorption isotherms exhibited the phenomenon of hysteresis, in which the equilibrium moisture content was higher at a particular equilibrium relative humidity for desorption curve than for adsorption. Figure 2.1 shows the hyterisis in chillies at measured temperatures.Sittiphong et al. (1992) reported the drying curves, drying characteristics, and drying constants of small and large chillies for air velocity of 0.18 m/s and temperatures of 55, 65 and 75oC. The drying curves for small and large chillies are shown in Figures 2.2 and 2.3, respectively. Drying characteristics curve for small and large chillies are shown in Figure 2.4 and Figure 2.5, respectively. It was reported that for both small and large chillies, the maximum allowable drying air temperature is 75 oC.
M
easurement of bulk density, loosely loaded in a container indicated that small chillies have a bulk density of 340 kg/m3 when newly harvested with a moisture content of 83% w.b., where as the bulk density of large red chilli is 325 kg/m3 with moisture content of 75 % w.b. After the moisture content is reduced to 13.0%, the bulk densities for the small and large chillies were reported to be 145 and 80 kg/m3, respectively.
Akpinar et al. (2003) reported the thin layer drying behavior of red chilli peppers. The experimental investigation was made by using a convective dryer with an inlet air temperatures of of 55, 60 and 70oC and a velocity of 1.5 m/s. It was reported that the drying times from the initial moisture content of 300% to a final moisture content of 10% d.b., at various drying air temperatures were between 160 and 300 min. Drying of red chilli in the ranges of 55–70oC and 1.5 m/s air velocity was found to be satisfactory.
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