Modeling and control of thawing phenomena in solute-impregnated frozen foods

This work was designed to give a better understanding and control of the me chanisms of simultaneous thawing and mass transfer occurring in a material in isothermal contact (T < 0 degrees C) with an aqueous freezant. Two model s of heat and mass transport in a porous medium were developed, one solved numerically and the other analytically. Despite different levels of simplif ication of the phenomena, simulations using both models demonstrated simila r mechanisms, including the progress of a sharp thawing front separating a frozen, non-impregnated inner layer from a thawed, highly impregnated outer (surface) layer. The work contributes not only to our understanding of the underlying mechanisms but also develops a very simple tool for predicting thawing/impregnation phenomena during cold immersion storage. The time-cour se changes in the thawing front and solute gain obtained experimentally wit h apple pieces and those predicted by the analytical model were in good agr eement, with only two food structure variables being identified for this pu rpose. The effect of process variables predicted by the analytical model wa s consistent with trends previously observed with real food, for instance a n absence of thawing if the food was stored in a biphasic mixture. (C) 2000 Elsevier Science Ltd. All rights reserved.