Staying in control of Mycotoxins
October 9, 2015
by Matthias Graeber
Mycotoxins are secondary metabolites produced by mold fungi and are an emerging threat for animal and human health.
Aflatoxin, deoxynivalenol (DON), zearalenone (ZEA) and ergot alkaloids probably create the most commercial concern, commonly affecting corn, wheat, rye, barley, oats and spelt. The highly-toxic aflatoxin is particularly problematic in corn as just a few highly contaminated kernels have the potential to make an entire lot unsafe for further use, even if the vast majority of grains are not affected.
Mycotoxins predominantly occur in concentrations that do not result in acute clinical symptoms of toxicosis. However, livestock may still show signs of elevated mycotoxin exposure, such as impaired growth, immunosuppression, and overall reduced performance.
Therefore, even when maximum permitted levels have not been set, it is advisable to follow guidance levels for feed (for instance, 8 parts per million (ppm) for DON in cereals and cereal products in the E.U.) from both an ethical and economical viewpoint.
Co-occurrence of mycotoxins
Analysis shows that it is highly likely that affected product is contaminated with multiple mycotoxins simultaneously. For example, a combination of the Fusarium toxins DON and ZEA, or a mix of aflatoxin B1 and fumonisins, may be present in corn lots.
This phenomenon is called co-occurrence and some combinations, such as aflatoxin B1 and fumonisins, are particularly worrying because there is evidence of a synergistic interaction of the two substances, intensifying the adverse health effects.
Co-occurrence can be explained by two biological mechanisms: First, some fungal species are able to produce different mycotoxins at the same time, such as Fusarium species producing deoxynivalenol and zearalenone.
Second, an affected product is likely to be infected by different species of fungi. Additionally, in compound feed, each component of the mixture can further exacerbate the problem by introducing different mycotoxins.
Researchers are now working to better understand the implications of co-occurrence on human and animal health.
Early intervention is critical
While good agricultural and post-harvest practice significantly reduces the risk of grain contamination, other factors, such as extreme weather, can cause plant stress, making the crop more susceptible to fungal infections.
Therefore, irrespective of the variability of the contamination profiles, it is business-critical that processors are able to rely on the performance of existing cleaning lines to be efficient and reduce toxin levels while removing only the minimum of good product. They also need to be confident that grain lots comply with commercial specifications and legal maximum levels of toxins.
Some regions have been hit severely in successive years, resulting in stockpiles of corn lots unfit for human or animal consumption. In response, processors have implemented advanced grain cleaning processes to prevent any initial contamination from spreading further by removing the small percentage of hazardous grains early in the value chain – not only in mills but also at grain elevator/reception facilities and warehouses.
Case studies show consistent toxin reduction
In 2012, The Bühler Group worked with Italian processors and leading scientists to successfully demonstrate that dedicated mycotoxin cleaning lines can effectively reduce aflatoxin B1 levels in contaminated corn lots – consistently below the European maximum level for feed of 20 parts per billion (ppb).
Two years later, the mycotoxin problem hit the same region again, this time shifting from aflatoxins, produced by Aspergillus species, to DON, produced by Fusarium species.
Although less toxic than aflatoxins, producers were on alert not to exceed maximum permitted levels of DON in product intended for food and to ensure they complied with commercial specifications and guidance levels for use in animal feed.
Reliable measurement of a mycotoxin concentration at ppb and ppm requires a statistically representative sample of the product, sample preparation, for example, by grinding and extraction, followed by chemical analysis using test kits or laboratory-based methods, such as high performance liquid chromatography (HPLC). Clearly, this approach is simply not viable for a grain flow of many tonnes per hour. However, by identifying the key physical indicators of the presence of fungal contamination, and removing kernels with these indicators by cleaning and optical sorting, it is possible to significantly reduce mycotoxin concentration.
But first, a central question to address is whether this approach remains valid even when multiple mycotoxins are present and the indicating properties change, due to varying contamination profiles. The figure to the left shows new findings from Bühler’s latest research in association with the Institute of Sciences of Food Production ISPA, Bari, Italy, at an Italian grain reception facility. It confirms the results previously obtained for aflatoxin B1, for the mycotoxins DON, ZEA, and fumonisins B1 and B2, which co-occurred at different levels in the investigated corn lots.
The study proves:
Broken kernels tend to foster higher contamination with levels ranging from 250%-400% of the respective mycotoxin, relative to the input concentration. This means separation by size is an essential first step in lowering mycotoxin levels.
Light product and dust from affected lots typically contain high levels of mycotoxins. This study highlighted increased concentrations of up to 1,200% of ZEA. Integrated or separate air aspiration systems can reduce this significantly, while further separation of lower-density grains, with noted levels of up to 180%-370% for the three different mycotoxins, decreases concentration to even lower levels.
Color defects are strongly associated with mycotoxin contamination. An advanced optical sorter targets color defects effectively and with minimal removal of good product. In the current study, relative levels of 272% and 529% have been measured in the rejected product for DON and ZEA, respectively.
The study concluded that the mycotoxin concentration of the cleaned product was reduced to 12%-31% of the initial concentration and revealed that all removed material had high concentrations of all three monitored mycotoxins. SORTEX optical sorting demonstrated outstanding selectivity in the removal of contaminated whole kernels.
It is this in-depth understanding of the key indicators of fungal contamination that has allowed Bühler experts to design standard flow sheets for mycotoxin reduction lines for different grains and contaminations. As the contamination profile and thus the indicators for a fungal infection may vary, it is essential to have a solid line of defense in place, which sequentially targets all relevant indicators of mycotoxins.
Bühler mycotoxin reduction lines are designed to help ensure a consistent and safe output quality, despite challenges imposed by natural variability and emerging hazards, enabling continued business success for grain processors. Several customer installations, at both grain reception facilities and mills, are already proving successful and demonstrating that return on investment can be achieved in less than a year.
Matthias Graeber is a mycotoxin expert with the Bühler Group, based in London, U.K. He can be reached at firstname.lastname@example.org.
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