Glass transition control of the detachment of food pastes dried over glass plates

A drying chamber with a device that allows the spreading of a uniform film of food paste over glass plates was developed with the purpose of evaluating the drying of paste-like materials assisted by the movement of solid bodies. The chamber temperature and the water content of the dried film made of maltodextrin, gum arabic or sugar cane molasses, were determined at the instant of detachment from the solid surface and compared with an empirically determined glass transition temperature curve. The results indicated that the detachment mechanism was controlled by the glass transition of the material. The lower the glass transition temperature of the film, the drier the film should be for detachment to occur. Thus the glass transition phenomenon can be used as a reference for the optimization of drying processes of paste-like material, as a guide for the design of dryers or in the formulation of food pastes. (C) 2003 Elsevier Ltd. All rights reserved.