Thermodynamic model of meat drying by infrarred thermography

Drying operation is one of the most important unit operations used to preserve meat products. Drying process involves a lot of mechanisms coupled together, and traditional kinetic theory of drying explains part of them, covering up the most important behaviors in the falling drying period. Therefore, it is necessary to determine the critical points of each transformation throughout the drying, and to analyse and quantify all of them. In this sense, an irreversible thermodynamic model has been developed, focusing on the falling drying period. In this work, infrared thermography has been used in order to obtain the evolution of meat surface temperature during drying operation. Infrared measurements were made with an Optris PI® 160 thermal imager (Optris GmbH, Berlin, Germany), with a spectral infrared range of wavelength from 7.5 to 13 μm. Surface water activity, volume, mass and moisture were obtained at different drying times. Drying analysis shows five stages, the traditional induction and the constant kinetic drying period (wet temperature of 22 °C) and three more stages in the falling drying period, shared out by the evolution of the surface internal energy and the vitreous transition.