Fracture events in rusk roll and the effect of changing water activity

E.M. Castro Prada, J.M.J.G. Luyten, T. van Vliet

Research output: Chapter in Book/Report/Conference proceedingConference paperAcademic


Crispness is a desired sensorial property of many foods, like bread. Both fracture properties and sound emission play an important role in crispness. With aging, bread crusts become less crispy. This is often ascribed to an increase in water activity of the crusts altering the mobility of the different molecules. However, it is difficult to relate the change in molecular properties directly to changes in crust behavior. One of the reasons is bread crust morphology, which is a heterogeneous cellular solid. A method was developed allowing to determine the fracture properties and accompanying acoustic emission of the individual fracture events. As a model for crispy products rusk rolls were selected. The amount of fracture events could be directly related to the morphology of the product, more precisely to the amount of beams and struts in the cellular solid. The method thus allows studying the solid material behaviour of the bread crusts independently from its morphology. This enables studying the relation between changes in the molecular behaviour and the fracture behaviour of the solid material. As an example, we showed the effect of water activity on the individual fracture events and accompanying acoustic emission.
Original languageEnglish
Title of host publicationProceedings 4th International Symposium on Food Rheology and structure, Zurich, Switzerland, February 20-23, 2006
Place of PublicationZurich
Publication statusPublished - 2006

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