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Practical application of postharvest continuous UV and pulse light treatments to reduce fungal and vomitoxin (DON) loads in corn

Principal Investigator: Tatiana Koutchma

Research Institution: Agriculture and Agri-Food Canada (AAFC)

Timeline: March 2020 – March 2023  

Objectives:

  • To determine the appropriate practical application of continuous and pulsed UV-C polychromatic light and LEDs as post-harvest treatments to reduce existing fungal loads on corn and to reduce ingress and spreading of fungi and DON.
  • To investigate contamination vectors and determine the most appropriate UVC treatment points: a) to reduce existing fungal loads, and b) to reduce ingress and spreading of fungi through cross contamination.
  • To evaluate the efficacy of polychromatic UV light (pUV) emitted by medium pressure mercury lamp to reduce F. graminearum and mycotoxin (DON) on the surface of corn and contact surfaces in a static regime. The effects of pUV on inoculated and naturally occurring fungi will be tested.
  • To evaluate the efficacy of polychromatic light emitted by pulsed lamp (PL) to reduce F. graminearum and the DON mycotoxin on the surface of corn and contact surfaces in a static regime. The effects of PL on inoculated and naturally occurring fungi will be tested.
  • To evaluate the efficacy of UVC light emitted at 275-280 nm using LEDs to reduce F. graminearum and the DON mycotoxin on the surface of corn kernels and contact surfaces in a static regime. The effects of 275-280 nm UVC LEDs on inoculated and naturally occurring fungi will be tested.
  • To develop a testing unit to integrate monochromatic and polychromatic light source with dynamic delivery of the kernels to the source. The light delivery to kernels in dynamic motion to achieve 3D exposure to light photons will be conducted.
  • To design and build the pilot unit(s) with monochromatic and/or polychromatic light sources based on the above experimental results; to measure the efficacy of the units in reducing F. graminearum and the DON mycotoxin on the surface of the corn.
  • To determine the most appropriate practical UVC treatment post-harvest and recommended practices for contact surfaces, air and corn via study and piloting.

Impacts:

  • The development of a successful pilot scale UV treatment system and practices that could help reduce postharvest losses and improve the quality of corn for sale by Ontario grain farmers.

Scientific Summary:

Gibberella ear rot in corn has long been a serious problem for farmers in Ontario. The disease can reduce grain yield, causing economic loss; but also its causative pathogen, Fusarium graminearum, can produce mycotoxins, deoxynivalenol (DON) in particular, resulting in food safety burdens and market value reduction. In the first study the feasibility of continuous ultraviolet (UVC) treatment at 253.7 nm was explored to reduce fungal (Penicillium verrucosum and F. graminearum) and mycotoxin loads on model surfaces, corn and wheat kernels. Reduction of F. graminearum (88.8%) on agar was achieved at UVC dose of 100 mJ cm-2 whereas naturally occurring Fusarium growth on corn was reduced by 60% with 1,000 mJ cm-2. The reduction of DON by 30% and 14%, ZEN by 52% and 42%, and OTA by 17% and 6% on corn and wheat, respectively, was achieved after exposure to 15,000 mJ cm-2 in static conditions. It was shown that postharvest UVC treatment of corn is feasible for reducing Fusarium at different points of the grain production, which could decrease mycotoxin accumulation. Despite no reported effect of UVC treatment on germination and protein content of grains, the established UV doses were an order of magnitude higher than exposures used in food and feed applications and hence require long exposure time.

In order to reduce treatment time and efficiency of UV light, this second project is proposed to explore the anti-fungal and anti-toxin effects of UVC LEDs, polychromatic UV (pUV) and pulse light (PL) on corn kernels, contact surfaces and air. The effects of LEDs, pUV and PL on fungi and DON reduction will be tested in a dynamic regime to test the UV technology for further commercialization.

The practical applications of UV treatment in corn harvest and post-harvest processing will also be explored. Optimization of UV exposure will be considered to maximize efficiency of the treatment thereby maximizing fungi-mycotoxin reductions. In addition, the practical application will investigate where ingress of fungi occurs and determine harvest and post-harvest control points via UVC exposure to reduce fungal growth and toxin accumulation.

External Funding Partners:

Agriculture and Agri-Food Canada (AAFC)

Funding for this project has been provided by Agriculture and Agri-Food Canada.

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