US and EU scientists researching how to crack through hard formations of bacteria on surfaces say their discoveries could lead to new cleaning methods for fruit, vegetables and other foods.

Scientists from the US Agricultural Research Service and the University of Navarra are studying how to improve the washing techniques used in the produce packing and processing industries. Food companies using fruit and vegetables for their products would also benefit from the research, which is available for companies to commercialise or use.

Conventional commercial washing and sanitizing methods to remove microbial contaminants from produce surfaces have been found to be marginally effective, the scientists stated. They are are conducting experiments to understand how these microorganisms survive and grow on produce surfaces even after exposure to sanitizing solutions like chlorine.

Bassam Annous, a microbiologist with ARS, and Joseph Sites, a mechanical engineer, recently developed a commercial-scale surface-pasteurisation treatment that resulted in a 99.999 per cent reduction in a population of Salmonella on the surface of artificially contaminated cantaloupe. The process involves immersing melons in water at 169˚F for three minutes to kill the pathogens, then sealing each melon in a plastic bag before rapid cooling in an ice-water bath.

The plastic bag prevents the fruit from potential recontamination in the cold water. The treatment not only enhances the safety of the fruit, but also extends its shelf life by reducing native microflora that may cause spoilage. And it did not harm melon quality.