Predictive equilibrium moisture content equations for yam (Dioscorea rotundata, Poir) flour and hysteresis phenomena under practical storage conditions

Fitting equilibrium moisture content data of food products into empirical equations is a first vital step in identifying acceptable mathematical expressions that could be subsequently applied in several food processing related operations. Adsorption and desorption (sorption) moisture isotherms were constructed for yam flour at the temperature of 27, 32, 37 and 40 °C, in the water activity (aw) range of 0.10–0.80. Effects of temperature were significant on the isotherms which appeared sigmoidal. Five widely recommended three parameters sorption models were fitted to the generated data from the gravimetric method. Desorption isotherms appears well fitted than adsorption isotherms. Over all, the modified Oswin (MOE) model describes the sorption characteristics of yam flour better than other models. Constructed moisture sorption plots showed a tendency of executing a closed loop (hysteresis loop) of which size appears to decrease as temperature increases.