Understanding the role of vitrification in drying-related phenomena

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This research program focuses on the interpretation of food drying-related phenomena such as shrinkage during air-drying, the applicability of Fick's law to any type of drying process, and the optimization of fruit epidermis mass transfer permeability for enhanced drying, through the concept of glass transition. The main objectives are: 1) to elucidate if Fick's law is valid only when the food is in glassy or rubbery states; 2) to understand the role of glass transition in shrinking of food materials during drying; 3) to analyze the possibility of developing biomaterials having skin and cellular tissues with selective permeability during drying by the use of ultra-low temperature pretreatments based on the relationship with glass transition. Glass transition temperature, Tg, can be defined as the temperature at which changes from the vitreous to the rubbery state occur in an amorphous system. Many food materials exhibit glass transition in the range of industrial temperature and moisture values during transport processes. The application of the knowledge learned in the area of glass transition of polymers to food systems had already been successful in understanding and predicting some behavior characteristics of foodstuffs during processing. Many other phenomena occurring during food processing, which are not fully understood yet, have also been related to vitrification. However, quantifiable expressions between food quality, processing and glass transition are unfortunately not yet available for these phenomena thus representing a great opportunity for development of state-of-the-art research in food engineering. The potential evolution of optimal drying techniques depends upon progress in basic research and upon the level of creativity in the design of dehydration processes. This research program will contribute to the production of "tailor-made" final products having desired properties by the integration of basic physical and chemical concepts to food processing, such as glass transition, in order to find practical relationships to define the quality of foodstuffs as well as to better understand the effect of processing on the final quality of transformed products.