ESTIMATION OF TEMPERATURE-DEPENDENT THERMAL-PROPERTIES OF BASIC FOOD SOLUTIONS DURING FREEZING

The thermal properties of food materials exhibit substantial changes w ith temperature during the freezing process. The estimation of these p roperties is very important in simulating freezing and in determining the freezing time of foods. Mathematical modeling of thermal propertie s 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 est imate thermal properties, namely the thermal conductivity and apparent volumetric specific heat, of aqueous solutions of basic food substanc es (sucrose, methylcellulose and wheat gluten) during freezing. Temper ature data from transient one-dimensional freezing experiments were us ed to estimate the temperature dependent thermal properties of these m aterials 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 th e experimental measurements for low concentration sucrose solutions. T he predicted apparent volumetric specific heats exhibited larger discr epancies with the estimated values at all sucrose concentrations. Furt hermore, the predicted thermal properties of methycellulose and wheat gluten did not agree well with the estimated thermal properties due to their complex molecular structures and non-ideal characteristics of t heir aqueous solutions.