Heat conductivity of some food products: theoretical models and practical measurements

Abstract

Thermo-physical properties are necessary for the design and prediction of heat transfer operation during handling, processing, canning, and distribution of foods. Thermal conductivity is defined as the ability of a material to conduct heat. There are steady-state and transient-state methods for measurement of thermal conductivity. The most commonly used transient methods are the thermal conductivity probe method, transient hot wire method, modified Fitch method, point heat source method, and comparative method. In this paper the modified Fitch method was used in order to measure thermal conductivity; the results were compared with the one predicted by some heat conductivity models: series model, parallel model, the weighted geometric mean method. Experimental tests and calculations were applied to the following food items: dry salami (salam uscat CrisTim); Transylvanian salami (salam ardelenesc); rustic sausage (parizer ţărănesc Caroli). The experimental tests were performed immediately after the products were purchased and then repeated after they were stored for one week, at 6°C. The results show that the series model adequately describes the heat conductivity for dry salami and rustic sausage, while the weighted geometric mean model is more appropriate Transylvanian salami, which has the lowest water content and the highest fat content.