Nondestructive monitoring of renetted whole milk during cheese manufacturing

A nondestructive ultrasonic measurement system was developed to monitor the rennet-induced coagulation of whole milk during cheese manufacturing. The ultrasonic attenuation coefficient during milk coagulation was determined by measuring ultrasonic wave amplitude and time of flight for a known distance. Total of 13 experiments were conducted in a laboratory environment at three temperature levels (28.0, 31.0, 34.0 °C) and for three rennet concentration levels (0.1, 0.3, 0.5 ml/1000 ml milk). The viscosity of the rennet-induced milk samples was also measured every two minutes simultaneously with the ultrasonic measurements. The coagulation start times determined from ultrasonic measurements were similar to the coagulation start times determined from viscosity measurements. The ultrasonic monitoring system was also tested in a cheese manufacturing plant and the system determined the coagulation start times.