Power Ultrasound Treatment of Fruits and Fruit Products

Power ultrasound used in food processing operations refers to mechanical waves with frequencies in the range beyond human hearing (20–100 kHz). The potential applications of power ultrasound in fruit processing and preservation are mainly those involving a liquid medium. The mode of action in such a treatment is attributed to cavitation, i.e., the generation, growth, and implosion of tiny bubbles in the liquid. Ultrasound can be used to enhance surface decontamination of fruits. Ultrasound showed promise for improving postharvest storage quality of plum, strawberries, and grape berry when it was applied alone or in combination with UV light or a chemical (ozone or ClO₂). As a result, an extended shelf-life and an increase in vitamin C or total flavonoids content was documented. Airborne ultrasound was reported to enhance hot air drying rate while ultrasound treatment in a liquid as a pretreatment shortened the time of a subsequent drying operation. Ultrasound was also effective in reduction of the survival count of a target human pathogen in fruit juices. Further study in pilot-scale units will help to determine the economical feasibility of the process for use in fruit-processing operations.