Estimation of temperature dependent thermal properties of basic food solutions during freezing

Abstract The thermal properties of food materials exhibit substantial changes with temperature during the freezing process. The estimation of these properties is very important in simulating freezing and in determining the freezing time of foods. Mathematical modeling of thermal properties of foods has been an appealing alternative to experimental methods. These models are generally based on the assumption that food materials are ideal binary solutions. The goal of this research study is to estimate thermal properties, namely the thermal conductivity and apparent volumetric specific heat, of aqueous solutions of basic food substances (sucrose, methylcellulose and wheat gluten) during freezing. Temperature data from transient one-dimensional freezing experiments were used to estimate the temperature dependent thermal properties of these materials during freezing using the Box-Kanemasu estimation method. The estimated thermal properties were then compared with values obtained from models found in the literature. Generally, the predicted thermal conductivities using the models were close to those estimated using the experimental measurements for low concentration sucrose solutions. The predicted apparent volumetric specific heats exhibited larger discrepancies with the estimated values at all sucrose concentrations. Furthermore, the predicted thermal properties of methylcellulose and wheat gluten did not agree well with the estimated thermal properties due to their complex molecular structures and non-ideal characteristics of their aqueous solutions.