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Journal of Food Engineering, Vol.40, No.1, 1-6, 1999
Predictive equations for thermophysical properties and enthalpy during cooling and freezing of food materials
Good knowledge of thermophysical characteristics of a wide range of foodstuffs has a major importance for the accurate prediction of their unsteady-state temperature distribution, the process duration and energy consumption in cooling and freezing (heating and thawing). Such information is necessary to predict the microbiology and biochemistry of spoilage and to control the product safety and quality, as well as for the design, optimisation and efficient operation of refrigerating and thermal systems in the food and biotechnological industries. The purpose of this paper is to present reliable unified equations for determination of the specific heat capacity, enthalpy, thermal conductivity, Kirchhoff function, etc, on the basis of generalised parameters (moisture content, actual and initial freezing temperatures). The relationship between the volumetric specific enthalpy and the Kirchhoff function is also derived. The proposed formulae have large areas of application. They cover practically all industrially processed food materials except those consisting mainly of fats. The equations may easily be used for both simple and rapid engineering calculations and for implementation in more sophisticated mathematical models and computer software, including the cases in which advanced enthalpy methods for numerical heat transfer simulations are involved.