Fractal Characterization of Some Physical Properties of a Food Product under Various Drying Conditions

Abstract

The present work was aimed at monitoring and studying the relationship between microstructural changes of a food product and its physical property changes during two different types of drying; i.e., conventional hot air drying and low-pressure superheated steam drying, using fractal analysis. The external changes of a model food product, viz. carrot, which were represented in terms of the percentage of shrinkage and the rehydration behavior, correlated well with its microstructural changes, which were represented by the rate of change of the fractal dimension of the microstructural images. The changes of physical properties and microstructure of carrot could be divided into two periods, which are periods of uniform and nonuniform deformation. The microstructural changes of the samples undergoing different drying techniques were quite different, however. Fractal dimension of carrot undergoing drying increased with drying time for both hot air drying and low-pressure superheated steam drying cases. Fractal dimension was found to be a good indicator of the microstructural changes of a product undergoing different drying techniques and conditions.

Keywords:

• Carrot
• Fractal analysis
• Hot air dryer
• Low-pressure superheated steam dryer
• Microstructure
• Shrinkage
• Structure-quality relationship

ACKNOWLEDGEMENTS

The authors express their sincere appreciation to the Commission on Higher Education, the Thailand Research Fund (TRF), the National Research Council of Thailand, and the International Foundation for Science (IFS), Sweden, for financial support. Our appreciation also goes to the Faculty of Fishery, Kasetsart University, for their help with the microstructural imaging of the samples.