Application of ultra-fine bubble technology to reduce Listeria monocytogenes contamination of fresh produce

The widespread distribution of Listeria monocytogenes in agricultural environments such as soil, manure and water results in frequent contamination of food processing areas. Although good agricultural practices partially reduce contamination, however, due to the open nature of farming, it is extremely difficult to completely prevent pathogen influx. Water used for washing or hydrocooling can act as a source of equipment and produce contamination with L. monocytogenes. Since this could lead to human infections, controlling L. monocytogenes in hydrocooling water and on the surface of fresh produce is critical for food safety. Currently used commercial disinfectants (chlorine, peracetic acid, quaternary ammonium compounds) are not completely effective in killing L. monocytogenes in wash water or on the surface of produce, especially in presence of organic load. Moreover, the presence of chemical residues and the formation of harmful organochlorine compounds is an occupational concern due to associated health risks, including cancer. Therefore, there is a need for developing novel strategies that could be employed (either alone or in combination with currently used commercial disinfectants) to control L. monocytogenes in wash water and on surface of fresh produce, vegetables and fruits. This proposal aims to investigate the potential of a new technology that employs water containing ultra-fine gas bubbles (size ~ 1 micrometer or less) for washing produce (celery, gala apples, romaine lettuce). We will generate ultra-fine ozone (UFO) bubbles in water using a high energy shear method and test the potential of resulting solution to rapidly kill (in 30 to 60 sec) L. monocytogenes in wash water and on produce surface. In addition, the efficacy of UFO bubble water to synergistically improve the Listeria killing potential of aforementioned commercial disinfectants will be tested. The anti-listerial efficacy of UFO bubble water will also be tested in presence of organic load. Potential impact from anticipated outcomes: Successful completion of this project will provide the produce industry with novel antimicrobial treatment for disinfecting wash water and produce in dump tanks, and single pass or re-circulated hydrocooling systems. This intervention will translate into increased microbiological safety of fresh produce.