Freeze dehydration by microwave energy: Part I. Theoretical investigation

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Abstract
A general unsteady state analysis is employed to derive a mathematical model of a freeze‐drying process using microwave heating. The model takes into account the variations of the transport and dielectric properties in the sample with both time and location as a function of temperature and pressure. The variations of the properties are described by functionals which have been derived from literature data and are built into the model.The mathematical model is used to simulate the freeze drying of beef meat with microwave energy at 2450 MHz. The simulation shows that drying rates are essentially a function of the microwave power input. The model also shows that the total pressure and the partial pressure of water vapor in the vacuum chamber directly affect the sample temperature during dehydration. The simulation shows, in particular, that, an optimal microwave freeze‐drying operation corresponds to an operation near corona and overheating/melting conditions.