We've all done it – thrown out fruit or vegetables because they went rotten. Fungal contamination is the most common cause of spoilage of fresh produce, with an estimated 30 percent of harvested fruit and veggies falling victim to it. Countermeasures currently including synthetic fungicides and pre-package sanitation treatments involving the use of chlorine or bromine. Now a team of scientists from Britain's Newcastle University have discovered that much more effective and human-friendly results can be obtained by treating produce with ozone.
Led by microbiologist Dr. Ian Singleton and plant biologist Prof. Jerry Barnes, the Newcastle researchers experimented with storing fresh fruit such as strawberries, tomatoes, grapes and plums in an environment that contained low levels of gaseous ozone. Not only was the production of fungal spores substantially reduced, but lesions on already-infected fruit became less visible. After eight days in the environment, the produce showed almost 95 percent less spoilage than would otherwise have occurred – depending on the specific fruit and pre-existing levels of infection.
It was also found that tomatoes exposed to ozone became more fungus-resistant, even once they were removed from the ozone gas. Exposed tomatoes were 60 percent less likely to develop fungal lesions, potentially boosting their shelf life by two to five days. While the scientists can't explain exactly what forces are at work behind the reaction, they suggest that some sort of memory- or vaccination-like effect is likely taking place. They are now looking into the specific amounts of ozone and lengths of exposure that work best for individual types of fruit and vegetables, as too much ozone can also cause spoilage.
"There are public concerns over pesticide residues on fresh produce" said Singleton. "Ozone is a viable alternative to pesticides as it is safe to use and effective against a wide spectrum of micro-organisms. Importantly, it leaves no detectable residues in contrast to traditional methods of preserving fresh produce."
In the case of the tomatoes, the amounts of ozone involved were said to be similar to those which the fruit would be exposed to outside on a sunny day.
The research was recently presented at the Society for General Microbiology's Spring Conference in Harrogate, England.