Evaluation of sorption isotherms in snacks with pregelatinized cassava

Abstract

Sorption characteristics are studied for their influence on the storage stability of dehydrated products and their effect on water vapour diffusion. In the present work, the adsorption curves of snacks with and without substitution of wheat flour by dehydrated cassava puree (PDM) were analysed using saturated salt solutions at 10, 30 and 50 ºC. Type III curves were obtained for the samples with PDM and type II for the control sample. Mathematical modelling was then performed using 8 different equations, obtaining the best fits for the Peleg (R2adjust =0.999-0.988), Ferro Fontan (R2adjust =0.998-0.970) and GAB (R2adjust =0.999-0.955) models. The values of the model constants in some cases turned out to be formulation and temperature dependent, and in general do not show a definite trend. This can be seen graphically as crossovers between the curves. This crossover of curves has been attributed to the increased exposure of hydrophilic groups due to increased molecular mobility at high humidity and occurrence of the glass transition in the system and/or endothermic dissolution of sugars.