Experimental investigations on drying kinetics, modeling and quality analysis of small cardamom (Elettaria cardamomum) dried in solar-biomass hybrid dryer

An indirect active solar-biomass hybrid dryer (SBHD) has been developed to study the drying kinetics, mathematical modeling, and quality of dried small cardamom. The experiments were carried out in hybrid (solar with biomass) and biomass mode to assess the performance of the dryer. Freshly harvested small cardamom with a moisture content of 82.4 % on a wet basis (w.b) was dried to 9.1 % (w.b) in hybrid mode. In biomass mode, moisture content was reduced from 83.2 to 9.5 % (w.b). The drying period of 19 h was sufficient in both modes of drying to attain the required final moisture content. The drying rate curve depicted that the small cardamom drying occurred under the falling-rate drying period in both SBHD and Biomass mode. In this study, non-linear regression analysis was performed to determine the drying behavior of small cardamom. Eleven empirical models were used to determine the coefficients of determination (R-2) and model constant for drying characteristics of small cardamom. Midilli model recorded the highest R-2 value of 0.992 and 0.988, least chi-square of 0.0001 and 0.0005, and RMSE of 0.0002 and 0.0002 for SBHD and Biomass mode, respectively. The average drying efficiency of 28.63% was observed for the drying of small cardamom in the SBHD while 23.98% was obtained from Biomass mode. The colour analysis showed that the retention of green colour was better in SBHD than biomass mode of drying. The biochemical analysis revealed that the small cardamom dried under SBHD retained the maximum percentage of oleoresin (3.30 %) and volatile oil (7.33 %) compared to biomass mode. The microbial quality of dried small cardamom was within the acceptable limit for both SBHD and Biomass mode.

Automated summary

The study showed that both the indirect active solar-biomass hybrid dryer (SBHD) and biomass mode are suitable for drying small cardamom, but SBHD has higher drying efficiency, better color retention, and higher content of oleoresin and volatile oil compared to the biomass mode.