Evaluation of ultrasonic techniques for on line coagulation monitoring in cheesemaking

Ultrasound detection techniques are interesting alternatives to monitor several industrial processes. It is known that they are nondestructive, noninvasive, robust and generally low cost when compared with other monitoring techniques. The evolution of the ultrasonic speed and the ultrasonic attenuation for compressional waves has been proposed by different authors as a tool to monitor the coagulation of milk. However, most of the studies published were performed in laboratory conditions, which not necessarily simulate the industrial process reality. In this work, the suitability of ultrasonic speed and ultrasonic attenuation for on-line milk coagulation monitoring was evaluated. Different experiments were conducted in order to study the potential of these techniques as well as possible limitations to their industrial use. The results obtained showed that both techniques could be applied in high controlled laboratory conditions, and could be used in experiments performed in parallel with the industrial process. However, limitations to their on-line application were also found. The main limitation for ultrasonic speed application was its strong dependence with temperature, whereas in the case of attenuation a deposition of an interfering element on the transducer's surface affected the results.