Effect of dimensions on the cooling rate of whole potatoes applying transfer functions

The evolution of temperature in the geometrical centre of potatoes during cooling was analysed using a transfer function approach. The response to a sudden change in the surrounding temperature was approximated assuming that the sample behaved as a delayed first-order system with unit gain. This model involves two parameters, the time constant and the dead time. These parameters depend on the product dimensions. Samples were assumed to have ellipsoidal shape. Expressions to estimate the time constant and the dead time from the three axes of the ellipsoid are presented. The temperature response in the geometrical centre subjected to changes in the surrounding temperature can be predicted using the model parameters. Good approximations between predicted and experimental values were obtained.