Air-coupled Transducers for Quality Control in the Food Industry.

Food industry is continuously innovating its capability of analysis by incorporating new technologies aimed to meet increasing quality and safety requirements, concurrence and consumers demands. In this context, non-destructive and non-invasive techniques are demanded in different stages of the production chain for quality control and verification. Air-coupled ultrasound is a fully non-invasive and non-destructive technique that has already been successfully implemented in other industries (aeronautical, aerospace, etc.) with fast scan velocities, and compatibility with industrial environment. This technique is capable to determine mechanical and viscoelastic properties of different materials as well as the presence of discontinuities, cavities, and foreign objects. Clearly, these capabilities are extremely interesting for inline quality control in the food industry. Being the main challenge of air-coupled applications the performance of air-coupled transducers (bandwidth and sensitivity), the objective of this work is to show a transducer design approach to simultaneously optimize both sensitivity and frequency band that make possible to operate in through transmission. In addition, food industry requirements in terms of materials and working conditions are also reviewed and included in the transducers design. Transducers with centre frequency at 300 and 500 kHz has been designed, built and tested. A first verification of the use of this technology in food products is shown revealing the possibility to measure transmitted signal above the noise level.