Changes in nutritional composition, functional, and sensory properties of yam flour as a result of presoaking

This study investigated the effect of soaking pretreatments on some of the properties of flour obtained from two varieties of yam namely;Dioscorea alata andDioscorea rotundata with a view of providing information that will enhance their end use. The yam varieties were washed, chipped, parboiled at 50°C, soaked for different periods (0, 6, 12, and 18 h), dried at 60°C, and milled into flour. The flour samples were analyzed for their nutritional composition, pH, color, and functional properties. The flour samples were also made into pastes and were sensorially analyzed and 0 h soaked samples were used as control. The protein content of 18 h-soakedD. rotundata andD. alata flour samples was significantly different from the control and soaking had no effect (P > 0.05) on the fat and ash content but the carbohydrate content of the flour samples ranged from 83.08% to 86.13%. The 18 h-soakedD. rotundata flour sample had the lowest peak viscosity, breakdown value, and final viscosity among theD. rotundata variety samples. Pasting temperature ranged from 79.80 to 83.60°C and 6-h soakedD. alata flour sample had the lowest water absorption capacity and the highest bulk density. On the basis of sensory analysis, the panelist preferred the taste, texture, color, and appearance of paste made from the 18-h soakedD. rotundata flour to the paste of other flour samples. The results of this study show that D.rotundata should be soaked for 18 h prior to drying and milling in order to obtain a good-quality flour and paste.