Molecular mobility in crispy bread crust

The aim of the PhD study on molecular mobility was to analyse the molecular grounds for the deterioration of crispy/crunchy characteristics of cellular solid foods. A fresh baguette for example has a crispy crust and a moist and soft interior. Moisture migrates from crumb to crust. Already at a water content of 9% (crumb contains around 45% water) the crispness of the crust decreases. During the study methods were developed to measure the speed of water uptake to test different ingredients on their potential to prolong crispness. Also the glass transition (which means an increase in mobility of the protein and starch molecules in the crust) and its relation with sensorial loss of crispness was investigated. The history of the crust in terms of water content and water activity as well as the morphology of the crust was found to be important for crispness and crispness retention.