YOUR PRODUCTION
Breaking the mould
New options for postharvest disease management
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lobally, 30 per cent of all food is lost or wasted. A large proportion of this is due to pests and diseases. If we could reduce this waste by 25 per cent there would be enough food available to feed 870 million people. At Murdoch University, we have developed a method to treat postharvest pathogens and insect pests, using the most abundant form of matter in the universe — plasma.
implications from a food safety perspective. A major advantage is that it also does not leave any chemical residues on the product. At Murdoch University, we are using cold plasma to treat the moulds that grow on fruit, vegetables and grain. To date we have trialled cold plasma for treating anthracnose (Colletotrichum spp.) on avocados (see Figure 1), Botrytis cinerea on strawberries, blueberries and raspberries, and also reduced mould growth on truffles. We have a grain project that is focussed on reducing the fungal pathogen Fusarium graminearum, which is associated with the production of mycotoxins. Mycotoxins are secondary metabolites produced by some fungi, that can cause many health issues and in some instances are carcinogenic.
One of the first activities that we undertake when beginning cold plasma trials is to Cold plasma can be test the impact of cold applied in the form of plasma on the product being treated. a flame or glow, air, or
Plasma is an ionised gas, and is produced naturally by lightning during a storm. Plasma technology is commonly used in television screens and neon lights and is also used in medicine and dentistry to treat wounds, so it is safe for human use. When we create plasma artificially it is at room temperature and is referred to as cold plasma. This low temperature avoids damage to the product being treated.
treated water.
Cold plasma has unique antimicrobial properties that can be used to reduce infection by bacteria, fungi (moulds) and viruses. Studies have shown that bacteria such as E. coli, Listeria and Salmonella are all dramatically reduced on food products following plasma treatment. This has obvious
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WA Grower SPRING 2020
This includes measurements on the colour, size and weight of the product, to ensure that the plasma treatment is not phytotoxic. Once this has been demonstrated, we look at the common pathogens that are associated with that product. Strawberries for example, are commonly associated with three key postharvest fungal pathogens, Botrytis cinerea, Phytophthora cactorum, and Rhizopus stolonifer. It is important to identify the main pathogens, so we can optimise the cold plasma treatment conditions for their treatment.
PHOTO Š MURDOCH UNIVERSITY
BY DR KIRSTY BAYLISS PLANT SCIENTIST, MURDOCH UNIVERSITY
FIGURE 1. AVOCADO BEING TREATED WITH COLD PLASMA. Cold plasma can be applied using different methods. We can apply it in the form of a plasma flame or glow, as shown in Figure 1. Alternatively, we can use plasma air, which is blown across the product or pumped into a package. A third option is plasma treated water, which is created by treating water with cold plasma, which draws the antimicrobial components into the water for application as a wash or spray. Treatment needs to be optimised for each product and pathogen being treated. In conjunction with the Strawberry Growers Association of WA, and the Agriculture Produce Commission, we are currently investigating the best method for application to punnets of strawberries, and will select the best treatment for larger trials.
