The effect of various drying methods on drying characteristics, sensory and nutritional qualities of yam

The effects of three drying methods: open sun drying (OSD), solar drying (SD) and solar adsorption drying system (SADS) on nutritional qualities, drying characteristics and sensory properties of dried yam were investigated. Three cultivars of white yam species (Dioscorea rotundata) and one cultivar water yam (Dioscorea alata) were subjected to various drying methods, i.e. OSD, SD and SADS. Proximate, mineral, vitamin C, water activity, colour and sensory of the processed yams and the fresh samples were analyzed using recommended methods. The initial moisture content of fresh yam cultivars ranged between 60 %-71 %. The initial moisture content did not have any regular relationship with the fresh content of ash, crude protein, and crude fat except carbohydrate, which showed some positive relationship. All the three drying methods significantly reduced the vitamin C content of sample however; there was no significant difference between SD and SADS methods. The reduction in the vitamin C content in OSD was much higher compared to the other two drying methods. Meanwhile, the vitamin C contents in Pona and Dente cultivars were relatively higher than other cultivars. The SADS and SD had similar effect on vitamin C and mineral content due to fact that the time of exposure to SADS was higher than that of the SD, while the OSD had higher effect on the vitamin C. In all the cultivars, the SADS, which is the combination of adsorption and solar drying, removed the free water faster than the SD system, which is only solar drying. However, OSD was less effective in terms of moisture removal compared to SADS and SD methods. Sensory evaluation results showed amala from SDLI had higher acceptability.
A thesis submitted to the Department of Food Science in partial fulfillment of the requirement for the award of the degree of Master of Science (Food Science and Technology), 2015