A computerised method for determining the thermal conductivity and specific heat of foods from temperature measurements during cooling

Abstract

A method is described for estimating the thermal conductivity, specific heat and the heat transfer coefficient to a spherical foodstuff, from the density of the food and temperature/time data at two points within the food during cooling. Three quantities were derived from equations describing temperatures at two points within a sphere during cooling, which are functions of thermal conductivity, specific heat, density and external heat transfer coefficient. Density was measured and the three other variables were determined. The relationships between these variables and the derived quantities were evaluated by multiple linear regression and expressed as polynomials. The first roots of these expressions were extracted by the Newton-Raphson technique and the expressions were then reduced in degree to yield subsequent roots. A routine was devised which selected the set of roots most appropriate to the original material. The values for thermal conductivity and specific heat estimated by this method were similar to values published in the literature. Although evaluated for spherical shapes, the method could readily be adapted to other simple geometric shapes.