UV Testing
UV treatments have been shown to reduce decay caused by common post-harvest pathogens.
Different wavelengths of light are able to reduce or eliminate a variety of agricultural diseases, bacteria and pests pre- and post-harvest. Anubhav Singh, assistant professor in food processing with UBC’s Faculty of Land and Food Systems, believes Canadian agriculture could see UV light installations for this purpose as early as 2024.
UV light has been used in agriculture and food production for a number of years for its germicidal and disinfection abilities. Now, UV treatments have been shown to reduce decay caused by common post-harvest pathogens.
Many studies have been done with UV-C light to control grain pests and fungus and provide delayed ripening among other benefits. UV-C light controls powdery mildew through denaturation (modifying the molecular structure of its protein) which causes damage at the DNA level of the disease.
Other pathogens UV light can completely kill include: botrytis (bud mold), Pepino, Clavibacter (cause of bacterial canker), Mycosphaerella (cause of black leaf streak) and Fusarium. Decay caused by common postharvest pathogens like Botrytis cinerea, Rhizopus stolonifer, monilinia fructigena and others has been reduced through UV treatments. Apples, peaches, strawberries, boysenberries, grapes and other produce have seen effective control of post-harvest decay through UV-C treatments.
Singh has been working with pulsed UV light since 2014 as a pre-harvest and post-harvest treatment. Part of the study compares pulsed UV light with regular, continuous UV-C and UV-B lamps. Singh isn’t the only Canadian researcher studying UV in food and berries. He notes that many others have done work on the subject before including other studies on pulsed UV light.
“Pulsed UV light is equivalent to giving a high intensity dosage, but in pulses,” he explains. “Producing pulsed UV-only light is tough, so we produce a high-intensity white light, about 10,000 times the intensity of normal sunlight, containing UV, visible and IR regions, so we get a magnified effect of all regions.”
Singh notes the study of UV light is important to growers and the food industry because it is a natural way to eliminate the need for other control products during handling and processing of agricultural products.
“Our current focus is on blueberries and grapes and wine,” he says.
The BC Blueberry Council is funding Singh’s work into UV light and control of common blueberry issues.
Pulsed UV light treatments on post-harvest white grapes and current studies of red grapes are showing great promise. Singh’s testing shows no significant detrimental effects on the physical chemistry or sensory parameters of the grapes following treatment. The treated white grapes appear to have far less deterioration than the untreated grapes.
“The positive effects of UV are quite dominant and well-established in literature. Its application will reduce use of pesticides and fungicides, which is what the consumer wants now due to the demand of natural and organic food products,” he notes. “The effectiveness is quite high and generally a dosage of about three to five kJ [kilojoules] per meter squared is considered sufficient for controlling disease and pests, although it does depend on the berry types and if light was able to reach the location where these pests are available.”
Additionally, water cleaning generally can’t penetrate microbe biofilms, yet the high intensity pulsed UV light does, allowing for better cleaning of tools used to process agricultural products.
Given that UV is light and can be applied at any stage of the food lifecycle from plants to harvested produce, it seems as though growers will be ready to embrace this new technology.
“We are slowly seeing that they are adopting and right now investing in this type of study,” says Singh. “I am sure we will start seeing Canadian installations of UV lights by 2024 or so. I am unsure though, if there would be any regulatory concerns. I also believe that food processing machinery will start integrating UV light into its cleaning cycle in the near future.”
Applications could be as simple as adding lighting systems in greenhouses or outdoor lamp-posts with UV lights. ■
