Moisture Adsorption Isotherms of African Arrowroot Lily (Tacca involucrata) Tuber Mash as Influenced by Blanching and Natural Fermentation

The adsorption isotherms of African arrowroot lily (Tacca involucrata) as influenced by blanching and natural fermentation were investigated at 10, 20, 30, and 40°C using gravimetric method. The BET, GAB, Oswin, Halsey, Henderson equations were fitted to the experimental sorption data and Clausius-Clapeyron equation was used to determine the isosteric heat of sorption. The equilibrium moisture content of the products at a given water activity is decreased by blanching and fermentation. The developed models, GAB, Oswin, Halsey and Henderson equations in that order provided good fit to experimental data. The BET monolayer moisture contents (Mo) values were lower than the values predicted by the GAB model. The surface areas for monolayer moisture sorption decreased with increasing temperature and blanching and fermentation reduced these values. Isosteric heat of sorption decrease at the average temperatures investigated with increase in moisture content. Blanching and fermentation offer perspectives to improve the shelf life of the product.