Predicting Temperature Changes in Freezing of Citrus Sections Contained in Steel Drums

Abstract

ABSTRACT GRAPEFRUIT sections commercially packed in standard drums (1.56 m^) suitable for shipment were frozen in a 22 C cold room. The time-temperature histories at both the inner wall and center of the cylindrical container were measured. The data are useful in controlling the growth of yeast and other microorganisms. The time required to freeze the product to 2 C of the room temperature were determined for a specific set of conditions. A simplified Fourier's heat conduction equation was solved by a finite difference method. The thermophysical properties were estimated based on the Mollier diagram for fruit and vegetable juices experimentally established by Riedel (1951). The Mollier diagram is considered to be applicable for fresh fruits as well as concentrated products. The numerical solutions obtained by the simplified method appear to fit the measured data with reasonable accuracy. The predicted patterns are in good agreement with the results for other products reported in the literature (e.g. Hsieh et al. 1977). The mathematical models are capable of predicting the effects of variations of processing parameters.