Infrared (IR) thermography applied in the freeze-drying of gelatin model solutions added with ethanol and carrier agents

Abstract

The objective of this study was to evaluate the heat transfer processes during the freeze-drying of gelatin model solutions (GMS) with ethanol and carrier agents, and to understand the relation of the temperature profiles with gel thermorheological behaviors and microstructural properties of the freeze-dried systems. Temperature variations caused by phase transitions were detected using an infrared thermograph camera. Temperature profiles have shown that in systems of GMS that use ethanol with or without sucrose, water removal has occurred more rapidly and at lower temperatures. The activation energies determined were reduced with the addition of sucrose. Shrinkage measurements and photomicrographs allowed visualization of the cavities left after the sublimation of the ice and showed the additive effects on the water removal rate. The lowest shrinkage values were obtained for GMS using ethanol with or without sucrose, and the highest shrinkage values were obtained for GMS using maltodextrin, which presented amorphous structures.