Monitoring physicochemical modifications in beef steaks during dry salting using contact and non-contact ultrasonic techniques.

In conventional ultrasonic techniques, the necessary contact between the sensor and the product has constrained the implementation of ultrasound for quality control purposes in the meat industry. The use of novel air-coupled ultrasonic technologies provides multiple advantages linked to contactless inspection. Therefore, this study aims to compare the feasibility of contact (C; 1 MHz) and non-contact (NC; 0.3 MHz) ultrasonic techniques for monitoring the physicochemical modifications undergone by beef steaks during dry salting after different times (0, 1, 4, 8 and 24 hours). Experimental results showed that the ultrasonic velocity increased during salting, which was linked to the reduction in Time-of-Flight ratio (R) and sample shrinkage (velocity C: R = 0.99; velocity NC: R = 0.93 and R C: R = 0.98; R NC: R = 0.95). In terms of the compositional changes provoked by salting, the velocity variation (△V) increased linearly (C: R = 0.97; NC: R = 0.95) with the salt content. As for textural parameters, hardness (C: R = 0.99; NC: R = 0.97) and relaxation capacity (C: R = 0.96; NC: R = 0.94) were well correlated with the △V through power equations. Experimental results reflected that the performance of the non-contact ultrasonic technique was similar to that of the contact technique as regards the monitoring of the physicochemical changes undergone by beef steaks during dry salting.