Measurement of food dehydration during freezing: development of an experimental tool and application to tylose.

When unpackaged foods are frozen, they lose water due to interactions with the surrounding media. This dehydration results in weight loss between 0% and 6% according to the product and the freezing process. This leads to quality and financial losses. A laboratory scale freezing cabinet was developed to measure food dehydration for various operating conditions from mechanical to cryogenic ones using liquid nitrogen. Experimental measurements were carried out with tylose plates as a food model material. The results show that the equipment offers a uniform gas flow velocity adjustable from 0 to 9 m/s and a uniform gas temperature adjustable from room temperature to -100°C. It was found that tylose weight loss can be estimated with a good reproducibility and that it is influenced by operating conditions. Based on these results, the developed tool might be useful to provide reproducible experimental data for real cases of food dehydration during processing.