Research led by Dr Ian Singleton, Dr Shreya Wani, and Prof Jerry Barnes from the School of Biology, investigated a new method that uses ozone gas to kill microbes that cause spoilage. Treating produce with ozone is sustainable and less costly than alternatives. Ozone doesn’t leave any residue, unlike pesticides or similar chemicals, as it simply transforms into oxygen.
Ozone is strongly antimicrobial and is used by the water industry to remove microbes from drinking water. However, it is currently not widely used in the fresh produce industry and provides a potential solution to a global problem in food production. It is well known in the industry that entire shipments of produce spoil before they reach market resulting in serious amounts of waste. Currently 1.3bn tonnes of food is lost or wasted throughout the supply chain each year.
What was the focus of the research?
Researchers exposed different types of salads to ozone including fresh spinach, coriander, rocket, water cress and lettuce. This yielded a 90% reduction in microorganisms, but the goal is to get it to 99%. Funding from the Institute for Sustainability allowed researchers to work on better understanding the reasons behind some microbes’ resistance to ozone.
Why is it important?
If we can understand the mechanisms underlying resistance of bacteria to ozone it may be possible to make them more susceptible. If the resistance can be overcome ozone could then eliminate 99% of bacteria on fresh produce, which would prevent spoilage saving both food and resources. Ozone is an effective method of reducing microbes on produce in some cases taking no more than 30 seconds to eliminate bacteria that cause spoilage.
Who could benefit?
The food industry and anyone involved in the transport of fresh produce. Organisations lobbying governments to implement ways to prevent food spoilage may also find this method useful.
What was found?
Key findings from this project and past research:
- In lorry containers or other transport environments ozone reduces spore production by fungi extending produce shelf life.
- When exposing produce to ozone in some cases levels need to be optimised to prevent discoloration.
- Bacterial cell age and prior cold stress exposure are linked to ozone resistance.
- Several genes important to resistance have been identified in cold adapted bacteria and several others in old bacteria.
- If transport time takes longer than expected ozone reduces ripening in the produce allowing it to be stored longer.
- Similar to vaccination, exposing certain products to ozone, such as tomatoes, activates oxidative stress defence mechanisms to defend the product against spoilage.
- Wani, S., Barnes, J., and Singleton, I. (2016) Investigation of potential reasons for bacterial survival on ‘ready-to-eat’ leafy produce during exposure to gaseous ozone. Postharvest Biology and Technology, Vol. 111:185-190 doi:10.1016/j.postharvbio.2015.08.007
- Wani, S., Maker, J.S., Thompson, J.R., Barnes, J., and Singleton, I. (2015) Effect of Ozone Treatment on Inactivation of Escherichia coli and Listeria sp. on Spinach. Agriculture, 5(2), 155-169 doi:10.3390/agriculture5020155
This research is from the project ‘Preventing food waste by waking the 'dormant' bacterium’ funded through our Responsive Mode Calls.