Combined modeling of thermal properties and freezing process by convection applied to green beans

Abstract

In this article a convective freezing procedure, based on five different air velocities, applied to green beans is presented. Equations to predict the initial freezing temperature, thermal conductivity and specific heat of a food product as a function of its composition and temperature are reported. These equations were coupled to the Tchigeov method, which predicts the ice fraction formed at temperatures below the freezing point for green beans. This procedure enabled the prediction of the thermal properties and the values obtained were in good agreement with data reported in the literature. Furthermore, a computational code in finite differences was developed to solve the transient heat conduction equation, transformed by the introduction of the enthalpy and Kirchhoff functions. This numerical model was used to fit experimental time-temperature data for freezing green beans. The procedure represents a useful method to predict the thermal properties and temperature evolution within a food product subjected to a freezing process.