Experimental Verification of Yam (Dioscorea rotundata) Drying with Solar Adsorption Drying

This work evaluates the yam (Dioscorea rotundata) drying performance of solar adsorption drying (SAD) compared to solar drying (SD) and open sun drying (OSD). The evaluation concerns the drying cycle for batches of yam, the effect on vitamin C, color and composition. As SAD can be applied during the night, by using air dehumidified by passing through a bed of silica gel, the cycle time for drying batches of yam can be reduced over 20–25% compared to SD and halved compared to OSD. SAD is thereby most effective during the first nights of drying when the driving force is the highest. Composition was not affected by drying methods but did affect vitamin C content. Vitamin C retention is not significant different for SD and SAD, but with a slight preference for SD. For three yam cultivars (‘Pona’, ‘Lilii’ and ‘Dente’), ‘Lilii’ dried fastest and ‘Dente’ drying slowest. SAD maintained 16 the whitish color of yam better than the other drying methods.