Sonodynamic therapy (SDT) is a robust treatment based on a combination of chemical compounds (sonosensitizers) and ultrasound processing that can be applied in food processing to improve the inactivation of a diversity of targets include foodborne pathogens and food spoilage microbes.

The objectives of the study carried out by Researchers from the University of California, Davis, (USA) were to evaluate the effectiveness of SDT systems that use food-grade sonosensitizers to inactivate selected food-borne pathogens in several liquid systems including aqueous and beverage models. Two ultrasound systems with different frequency and intensity coupling with food-grade sonosensitizers are employed in this study. The kinetic inactivation models are constructed to quantify the bacterial reduction of the SDT treatments using the standard plate count method. After the synergistic bacterial inactivation is confirmed, the biochemical changes in the treated cells are characterized to study the potential pathway of the inactivation. The bactericidal mechanisms to be studied focus on cellular apoptosis indicators including membrane damage, oxidative stress and the suppression of metabolic activity.

Results showed a significant synergistic bacterial inactivation over the selected bacterial models in a short period of treatment time. The bacterial models were E. coli O157:H7 and L. innocua strains as representatives of gram-negative and gram-positive bacteria. We observed that the SDT treatments achieved 5-to 6-log CFU reduction (P< 0.01) for both of the tested bacteria within 15 minutes in aqueous solutions. When applied in beverage models, the SDT treatments showed enhanced decontamination of 5 to 6 logs CFU (P< 0.01) within 10 minutes while product quality attributes remain unchanged. The treated bacteria showed signs of cellular apoptosis include significant membrane damage, intracellular oxidative damage, and enzymatic activity suppression.

The results of this study published in Journal of Food Protection demonstrate the potential of sonodynamic therapy as a rapid and highly effective food processing method for improving the sanitation of food products without compromising food quality attributes.