New research into mycotoxins – fungal pathogens that can cause serious health issues
Dr Brett Greer is a Senior Research Fellow at the School of Biological Sciences at Queen’s University Belfast. Here, he shares the findings of his safefood-funded research into mycotoxins in cereals for human consumption.
What are mycotoxins and what food safety threat do they pose?
Mycotoxins are fungal pathogens that are naturally produced by fungi (moulds) and which can have serious implications for human and animal health, with the main route of exposure being through ingestion of contaminated food/feed. Their health effects range from kidney and liver damage, and gastrointestinal issues, to acute poisoning and longterm effects such as immune deficiency and cancers. They are also known to cause sickness, with one of the main mycotoxins, deoxynivalenol (DON), also being known as vomitoxin. They naturally contaminate the majority of cereal grains such as oats, barley, wheat, corn, maize etc. while growing and in storage.
The type of fungus and the mycotoxins produced are very much dependant on the climate in which the cereal is grown, with climate change expected to drive the contamination of these crops, necessitating greater surveillance and control to safeguard the food chain. Of the hundreds of mycotoxins identified, only twelve have been legislated for in human food and animal feed, including; Aflatoxins, fumonisins, ochratoxin A, zearalenone, deoxynivalenol, T-2 and HT-2 toxin, with the latter two (T-2 and its metabolite HT-2) being important mycotoxins in the oat industry on the island of Ireland.
Can you share the objectives of your research?
There were several objectives in this research project, including:
• Review the current commercially available rapid screening methods for the detection of the T-2 and its metabolite HT-2 in cereals for human consumption;
• Conduct a comprehensive survey of oats and barley to determine the mycotoxins that frequently contaminate these cereals in Ireland and the UK;
• Analysis of oat samples before and after processing to assess the impact of the processing procedure on the levels of T-2/HT-2.
Cereal grains such as oats can be analysed at the farm or facility, where they are processed for human or animal consumption. In this case, commercially available rapid diagnostic kits were used to analyse oat samples; these are usually used for screening, i.e. to check if something may be present, and are not confirmatory.
This type of analysis is rapid due to the requirement for an answer as soon as reasonably possible in order for a batch to be released after processing, and in fact, the same technology was used for COVID testing. In comparison, testing laboratories generally use confirmatory methodologies that are usually performed on more (expensive) technological platforms such as liquid chromatography coupled to mass spectrometry (LC-MS), with this technology considered the gold standard in the industry. LC-MS instruments, although more expensive and analytically complex, give an end result that is fully confirmatory, accurate and provides more information in regard to other mycotoxins possibly present.
One of the main objectives of the project was to evaluate the accuracy of the commercially available rapid test(s) used by the industry, with several test kits for the analysis of T-2 and its metabolite HT-2 compared against the same sample analysed by LC-MS.
What were the key findings of your study?
One hundred oat samples were analysed using several of the commercially available rapid test kits, with the results compared to the same samples analysed by LC-MS (gold standard). Overall, with the current legislative standards for the control of T-2 and HT-2 toxins in oats, two of the commercially available rapid test kits demonstrated reliable results when compared with LC-MS, including the number of false negative/false positive results generated. In terms of unprocessed oats, T-2/HT-2 toxins were detected in 94% of samples, with 16% of unprocessed oat samples exceeding the current EU indicative limits set for the sum of T-2/HT-2. In addition, unprocessed oat samples were analysed for other regulated mycotoxins such as deoxynivalenol and zearalenone, with their reported concentrations well below their respective legislative limits, while another mycotoxin, ochratoxin A, exceeded its legislative limit in 3% of unprocessed oat samples.
Another finding was the co-occurrence of T-2/HT-2 and deoxynivalenol, T-2/HT-2 and ochratoxin A, and T-2/HT-2 and zearalenone, with one sample containing all four of these mycotoxins. This is important because co-occurring mycotoxins can have an effect greater than their sum. In regard to the processing of the oats to the finished product for human consumption, although the prevalence of T-2/HT-2 was still high (94%), no regulatory violations were observed, indicating that the industrial processes used are effective in reducing contamination levels of these toxins in oats. Similarly, the other regulated mycotoxins, such as deoxynivalenol and zearalenone were detected in the finished product after processing, albeit at concentrations well below the legislative limits.
How do these findings impact consumers and the food industry?
In terms of the unprocessed oats, 16% of samples tested were in breach of the current EU indicative limits set for the sum of T-2/HT-2 (1,000 μg/kg). However, if the regulatory limits are halved from 1,000 to 500 μg/kg, 34% of samples would exceed these new limits, doubling the original number of samples that would be non-compliant. Furthermore, although none of the processed oats that were tested exceeded the current EU guideline values, halving these values, [as mooted by the EU], could lead to some processed oat samples exceeding the new thresholds, thereby increasing the number of non-compliant samples and creating challenges for the sector.
What are your research recommendations for improving mycotoxin control and monitoring in the cereal processing industry?
At present, I am working on another mycotoxin-related project alongside leading EU experts, Mycotox-I, which aims to assess the risk of mycotoxin contamination of cereals produced on the island of Ireland, focusing predominantly on oats. There are several parts of the project, with the overall aim of reducing the natural contamination of oats by mycotoxins as much as possible.
To do this, various factors will be assessed, including the growing, storage and processing of oats to produce the final product for consumption. State-of-the-art analytical tools including LC-MS will be used to analyse the mycotoxin levels produced by mycotoxin-producing fungi from various trials carried out in both glasshouse and field experiments. The field-based surveys will determine the prevalence of fungi and the subsequent mycotoxin levels, with post-harvest analysis used to determine the levels of mycotoxins in the final milled product after processing. The glasshouse and field-based studies will help to determine how disease management systems can reduce mycotoxin levels under current and future climatic scenarios, with the aim of reducing the use of fungicides by 50% by 2030.
By using state-of-the-art machine learning technology in conjunction with data on the weather (e.g. rainfall and temperature), oat variety, and previous crops grown in the field, it is hoped a new decision-making system will be tailored for Irish agricultural systems in order to support the industry and reduce the mycotoxin load in food produce. For more information, please see www.safefood.net/ research
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