Thermal Conductivity of Liquid Foods—a Review

Theoretical and semi‐empirical models for estimating the thermal conductivity (k) of liquid foods are reviewed. Seven models were considered; five, all containing temperature as an independent variable, were selected for their simplicity and apparent accuracy for further study and statistical evaluation. Experimental k values of 158 food samples, such as fruit and vegetable juices, sugar solutions, egg white and dairy products, were obtained from the literature. The model by Riedel (1949) described the data the best, producing the lowest standard error in the estimation of experimental values. Using thermal conductivity of water would give errors almost four times as much as if the Riedel model was used. These semi‐empirical models could also be used to estimate average k values in processes where temperature and/or solids content were varying. Theories of thermal conductivity applicable to liquid food systems were reviewed.