SHRINKAGE DURING DRYING OF FOODSTUFFS

Experimental shrinkage data as a function of water content for particles of potatoes, apples and carrots of different geometry and under various drying conditions are presented. Volumetric shrinkage of individual particle is affected mainly by air velocity; other drying variables have negligible effect. Changes in surface area to volume ratio with water content are practically independent of drying conditions but dependent on sample geometry and the type of foodstuff. A simple model in which volumetric ratio is represented by one or two line segments is developed. The shrinkage of packed beds is also studied. Changes in bed volume during drying are almost only a function of bed-averaged water content. A simple way of predicting porosity in the bed is applied and its results are compared with experimental data.