Comparison of Water Adsorption Characteristics of Plantain and Cocoyam in a Controlled Storage Condition.

Abstract

This investigation was conducted to study the behaviour of dehydrated products of cocoyam and plantain in a controlled storage environment at temperature range of 25 and 40^oC.  Salt solutions were used to achieve water activity that ranged from 0.08 to 0.97.  Equilibrium moisture content obtained was used to produce sorption isotherms at these temperatures.  Sorption models of Halsey, Chung Pfost, and Henderson were evaluated on the experimental data as well as modified versions of Halsey and Henderson. Co-efficient of determination ranged from 0.80 to 0.97 in all the models. Most equilibrium moisture content obtained during the experiment reflected adsorption except for very low water activity.  Chung Pfost equation gave the best fit for the absorption characteristics of these crops having the least residual mean square within 0.03 to 0.11%.  Plantain exhibited higher affinity for water than cocoyam in all the relative humidity range. Least moisture content derived for storage stability of these crops varied from 6.5 to 8.2 and 6.3 to 8.2 % in cocoyam and plantain respectively. The region of local isotherm II of relative humidity between 23 and 65 % was identified as the region for optimum storage.

Keywords: Equilibrium moisture content, sorption isotherm, storage stability and water activity