Experimental and numerical characterization of food dehydration during freezing

Abstract

Using freezing in industry means understanding and controlling the process, particularly in terms of heat and water transfers. Water transfer is responsible for food dehydration during freezing which represents weight losses up to 6% according to the product characteristics and the freezing process. A model of heat and mass transfer during the freezing process was developed. It takes into account not only heat transfer and crystallization but also water transfer, evaporation and sublimation. A methodology was established to identify some important and correlated model parameters: water activity, initial freezing temperature and ice fraction from the enthalpy-temperature curve of a product. The model allows predicting the freezing time and weight loss for a given non-porous product (initial temperature, composition, geometry, dimensions, and physical properties) and a given freezing process (temperature, hygrometry, convective heat transfer coefficient). The numerical results were compared with experimental data obtained with Tylose in a pilot plant freezer from −30 °C to −100 °C.