Effect of different drying methods on the functional and physicochemical properties of the flour of selected yam cultivars in Ghana

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Yams (tubers of the Dioscorea spp.) which are highly consumed in most parts of the world suffer great deal of postharvest losses after harvesting and during storage due to the high moisture content. Drying of yams is one of the most important methods of preservation so as to minimize postharvest losses and to extend products shelf life during storage. The effect of different drying methods (open sun, solar and solar adsorption drying) on the functional and physicochemical properties of the flour of selected yam cultivars in Ghana was investigated. Two yam varieties, Dioscorea rotundata (Pona, Dente and Lilii) and Dioscorea alata (Matches) were used. The properties studied included solubility, swelling power, water binding capacity, amylose and amylopectin ratio, granule size, pH, and colour. The drying process indicated that different yam cultivars are influenced differently during drying. The difference in drying behaviour may be due to structural differences. In view of this the functional and physicochemical properties of the yam samples were differently affected. With the exception of amylopectin content, solubility and pH values which were higher in the solar dried and open sun dried yam samples, the values for the amylose content, swelling power, water binding capacity and colour were lower than those of the solar adsorption dried yam samples. The drying methods showed significant effect (P < 0.05) on the properties of the yam flours. The results indicate that different drying methods have some profound effect on the granule size and other functional and physicochemical properties of yam flour. The interrelationships between the drying methods, cultivars, functional and physicochemical properties were evaluated with SPSS 20 by Pearson correlation.
A thesis submitted to the Department of Food Science and Technology in partial fulfillment for the award of the degree of Master of Science in Food Science and Technology, 2014