Individual Fracture Events in Cellular Foods

Crispy foods like biscuits and breads crusts are cellular solids with relatively large pores of a wide size distribution. Important for the crispy character of such products are both the fracture behaviour and the acoustic emission (Luyten et al. [1]). With aging under deteriorating conditions, these products become less crispy. This is often ascribed to an increase in water activity of the crusts resulting in a change in the mobility of the different molecules, and thus a change in the solid material properties. However, it is difficult to relate directly the change in molecular properties to changes in crispy behaviour. One of the reasons for this is the product morphology, dry crispy foods are irregular built cellular solids. An example is given in Fig. 1.