Improving safety of vegetable produce through on-farm sanitation, using electrolysed oxidising (EO) water (VG15068)
What’s it all about?
This investment began in mid-2017 to test whether ‘electrolysed oxidising’ or ‘EO’ water can be used to increase the quality of vegetable irrigation water. This electricity-charged sanitisation approach, and how it could benefit the Australian vegetable industry, was described in more detail in this news article from Hort Innovation, released when the project was first announced.
Specific project activities include comparing the efficiency of EO water with that of other options for treating irrigation water for relevant water-borne pathogens; discerning whether EO water treatment can prevent potential microbial contamination or fresh produce pre-harvest; assessing the ability of EO water to control soil pathogens, and any effect on important soil microorganisms; and ultimately developing protocols for EO water adoption by Australia’s vegetable growers.
This project is evaluating the use of electrolysed oxidising (EO) water for on-farm sanitation of irrigation water and fresh produce. Earlier greenhouse studies showed that EO water was effective for pre-harvest sanitation and the next step is to field test the technology.
For the on-farm trials, the research team decided to use an in-line ‘booster’ electrolysis treatment system that generates free chlorine from natural salts contained in the irrigation water. This system offers considerable on farm-advantages compared with conventional instrumentation, however it required further laboratory analysis.
The team tested the booster system for its ability to reduce microbial contamination on test microorganisms in a range of water samples, including real farm water samples. The results to date have shown good potential for in-field use.
A trial site has been established with a lettuce grower at Virginia in South Australia, to install and test the irrigation water disinfection technology. Initial testing of the irrigation water treatment system has now started, with data collection ongoing.
At this stage, all travel for field trials has been suspended by the University due to COVID-19 restrictions. If field work can restart, plant growth tests with disinfected water will be conducted in the next 3 months.
The project team has conducted a study to test how well EO water reduced contamination on lettuce, spinach and parsley plants grown under hydroponic conditions in a greenhouse.
Plants were exposed to three pathogens—E.coli, Listeria and Salmonella—and then watered with tap water or EO water or sodium hypochlorite (NaClO), at a range of concentrations.
They found that irrigation with 20 or 50 mg/l available chlorine EO water was more effective at decontaminating the plants, compared with the unwashed or tap water controls.
While sodium hypochlorite was also a good decontaminant, it caused visible damage to plant leaves at 50 mg/l available chlorine, while EO water at the same concentration did not.
There were no negative effects of pre-harvest irrigation with EO water on post-harvest shelf life, with all leaves showing excellent storage qualities for periods of up to 14 days.
In summary, EO water is effective for pre-harvest sanitation. Next steps are to investigate the effects of EO water on soil microbes and field testing.
This project is a strategic levy investment in the Hort Innovation Vegetable Fund