Ultrasound is a pressure wave that is oscillating at a frequency above that of human hearing. Ultrasonic waves have any frequency above 20 kHz up to a practical limit of around 10 MHz for various applications. Within this band, the measurement of the speed of propagation, the attenuation, or the reflection of ultrasonic signals can be the basis of instrumentation systems for the food industry.
Using ultrasound, full reproducible food processes can now be completed in seconds or minutes with high reproducibility, reducing the processing cost, simplifying manipulation and work-up, giving higher purity of the final product, eliminating post-treatment of waste water and consuming only a fraction of the time and energy normally needed for conventional processes. Several processes such as freezing, cutting, drying, tempering, bleaching, sterilization, and extraction have been applied efficiently in the food industry. The advantages of using ultrasound for food processing, includes: more effective mixing and micro-mixing, faster energy and mass transfer, reduced thermal and concentration gradients, reduced temperature, selective extraction, reduced equipment size, faster response to process extraction control, increased production, and elimination of process steps.