Effect of Heat-Moisture Treatment on Equilibrium Moisture Content Models for Cassava Starches

Abstract

The level of water contained in food products is known to affect several unit operations in food processing including drying, storage, and thermodynamics phenomena which are related to the sorption attributes of food. Heat-moisture treatment as an aspect of the thermodynamic properties of the food affects sorption phenomena and invariably the associated empirical models for the sorption behaviour.

In this study, effect of heat-moisture treatment on sorption moisture isotherms for cassava starch at 27, 32, and 37^oC, respectively was determined for selected cassava genotypes (TMS 97/4763 and TMS 98/0510) including its impact on equilibrium moisture content (EMC) empirical models. The moisture isotherms were sigmoidal indicating effect of temperature and show the influence of the heat pre-treatment. Six widely recommended three parameters sorption models were fitted to the EMC data from the gravimetric method. Desorption isotherms appears well fitted than adsorption isotherms. Analysis shows that due to the heat-moisture treatment, the Modified Oswin Equation (MOE) and Modified Halsey Equation (MHE) models are the preferred empirical equations for the modelling of the emc data for the cassava starches.

Keywords: Cassava starch, equilibrium-moisture-content, heat-moisture treatment, sorption, isotherms.