PREDICTION OF FREEZING TIMES FOR FOODS IN RECTANGULAR PACKAGES

Abstract

ABSTRACT A previous study of methods for predicting the freezing times of slabs, cylinders and spheres was extended to cover rectangular bricks of food materials. Experimental measurements of the freezing time were made over a wide range of conditions using a food analogue material, and these results compared to times calculated from various available prediction methods. The three‐dimensional version of a three time‐level finite difference scheme was found to be the most accurate numerical solution. Simple formulae are available for predicting the freezing time of rectangular bricks using the geometric factors derived by Plank. These factors are shown to be subject to error, and none of this group of methods gave accurate prediction of freezing time. A previously proposed group of formulae are extended to cover rectangular bricks. These formulae are simple to use and accurate. They are applicable to slabs (±5% with 95% confidence), and to cylinders and spheres (±7% with 95% confidence) as well as to bricks (±10% with 95% confidence). These extend the previously published formulae for slabs, cylinders and spheres without significant loss of accuracy.