Effect of Drying Method on the Microstructure and Physical Properties of Dried Apples

The purpose of this study was to determine the influence of the internal structure of dried apples on such physical properties as density, porosity, or shrinkage. Apple slices were dried using convection, microwave-convection, and infrared-convection methods. The apple slices dried by means of the microwave and infrared methods showed between 11 to 12% lower shrinkage, 30-34% lower volume, 18-23% lower density, and porosity of 25-28% higher than the slices dried exclusively by the convection method. Considerable differences in the density and porosity of the apple slices dried using the above methods were confirmed by analyzing the tissue images made with the help of scanning electron microscopy. Convective drying caused significant changes in the actual size and distribution of the apple cells. The cells dried using both the microwave and infrared methods had a larger cross-sectional area compared with the convective-dried material.