Ultrasound cleans fruit and vegetables
Reports of food-borne illness outbreaks are on the rise and are usually caused by pathogenic bacteria contaminating fresh produce. Currently, produce is washed with antimicrobial liquids pre- and post-harvest, but these treatments are not always effective and may cause health problems in themselves. The EU-funded DITEC (Development of novel disinfection technologies for fresh produce) projected investigated whether these antimicrobial liquids can be replaced with ultrasound treatment. Researchers treated lettuce with Escherichia coli, a common food-borne bacterium, and studied the effect of ultrasound treatment on the E. coli population. They studied the effect of using ultrasound combined with the essential oil of oregano (EOO). The structural properties of the surfaces and the histology cross-sections of the treated samples were analysed by scanning electron microscopy and light microscopy imaging. In both cases, E. coli was killed or inactivated by the ultrasound treatment. It was also found the EOO enhanced the effects of the ultrasound treatment. Neither treatment caused structural differences or damage to the structure of the lettuce leaves. Researchers also found that ultrasound combined with chlorine dioxide reduced E. coli and Salmonella in inoculated alfalfa and mung bean sprouts. In addition, scientists identified the main antimicrobial species generated by CAP and their effect on the growth rate of E. coli on butterhead lettuce leaves. Finally, the ultrasound system was applied in combination with ultraviolet-C light in order to treat lettuce wash water. This treatment resulted in the highest bacterial inactivation, colour reduction and reduction of organic matter after 30 minutes of treatment. DITEC successfully developed sustainable alternative techniques for disinfecting fresh and fresh-cut produce that can improve quality and extend shelf life. Furthermore, these new approaches will reduce water usage, waste and the need for chemical treatment. Thus, project work will have a positive effect on both human health and the environment.
Keywords
Ultrasound, fruit and vegetables, cold atmospheric plasma, DITEC, essential oil of oregano
