Time matters when ultrasonicating beef: The best time for tenderness is not the best for reducing microbial counts

Research on the effects of high-intensity ultrasound (HIU) on meat quality properties shows contradictory results. The latter has been sometimes attributed to limited exposure time, not enough to cause cellular modifications. This study evaluated the effect of different exposure times (0, 10, 20, and 40 min) of HIU (37 kHz, 90 W cm(-2)) on physicochemical properties including; pH, color, tenderness, and microbial counts of two different portions of beef Longissimus lumborum (cranial-caudal). No significant effect of loin portion was observed (p > .05). Ultrasonication time caused a 20.7% toughness reduction of beef (p < .05). However, ultrasonication time also increased hue from 0.62 to 0.76 from red to orange values (p < .05), but it did not affect important coordinates such as a* or C*. Ultrasound caused an increase in the pH from 5.46 to 5.6 (p < .05), but pH was not affected by the time. The highest tenderness was achieved at 40 min of sonication. Significant reductions of mesophiles, psychrophiles, and coliforms were observed after ultrasonication when compared to control (p < .05). The best ultrasonic condition for microbial reduction was at 10 min, when the lowest microorganism counts were achieved, with a subsequent growth when increasing ultrasonication time. Practical Applications High-intensity ultrasound application appears to be a promising method to increase tenderness in beef. However, optimum time, intensity, and methodology for its application have to be defined, because the variations may affect other quality characteristics such as color or microbial contamination. To find ideal parameter values may help the industry to take decisions on the design of specialized equipment for ultrasonication of meat.