Mechanical properties that govern how, and under what conditions, a structure fails when force is applied. In food texture science they describe how foods fracture during biting and chewing — crispness, crunchiness, brittleness — and are measured by instrumental texture analysis to predict sensory quality. Texture analysers record force–deformation curves whose peaks and jaggedness quantify crispness in snacks, snap in chocolate and crumbliness in biscuits; acoustic emission adds the audible crunch dimension. Formulation levers — moisture, fat, starch gelatinisation — tune fracture behaviour, and staling or moisture uptake degrades it, a key shelf-life failure mode.