Adsorption and desorption isotherms of noodles produced from composite flour of wheat and water yam (Dioscorea alata)

Adsorption and desorption isotherms of wheat-yam noodles at 32 and 37 degrees C were estimated with the standard static-gravimetric method. The composite flour of wheat and water yam (D. alata) were mixed at ratios of 75:25, 50:50, and 25:75% to produce the noodles with the use of a locally fabricated extrusion-like hand-operated machine. Experimental data were fitted to four mathematical models (Guggenheim, Anderson and de Boer; modified Guggenheim, Anderson and de Boer; Oswin and modified Oswin). The constants of the sorption equations were evaluated using nonlinear regression analyses. The moisture sorption isotherms were sigmoidal in shape and influenced by temperature. The equilibrium moisture content increased as the relative humidity increased in adsorption and desorption isotherms. The sorption models evaluated predicted the adsorption and desorption isotherms of wheat-yam noodles at the evaluated temperatures adequately, with R-2 >= 0.9680. Thus, these models are suitable for predicting the equilibrium moisture content of wheat-yam noodles under the practical storage conditions studied.