We use a universal testing machine to study macroscopic mechanical properties, i.e. firmness and texture. Firmness of fruits and vegetables is our reference for structural and mechanical studies at lower scales. Typical macroscopic measurements of mechanical properties in puncture, compression, tension or three-point bending have been completed as the acoustic emission signal was monitored. The acoustic emission signal was recorded by a contact sensor which substantially improves the signal-to-noise ratio. Moreover, from the consumer’s perspective, the acoustic signal transferred through the bones is the primary source of crispness evaluation. We have used this result to develop a stand-alone device for instrumental evaluation of apple texture called a CAED (contact acoustic emission detector). In general, we use acoustic emission to detect the onset of cracking and to follow the destruction process.
