The Mycotoxin Threat in Grains and Pseudocereals
Mycotoxins are toxic secondary metabolites produced by fungi, which can contaminate a wide range of agricultural crops, including cereals and pseudocereals like buckwheat. While the presence of mycotoxins in buckwheat has been documented, studies suggest that mycotoxin levels in pseudocereals are generally lower compared to traditional cereals like wheat. However, contamination can still occur during different stages, such as crop growth in the field and improper storage after harvest, especially under humid conditions. Several mycotoxin-producing fungal species have been identified in buckwheat, including Aspergillus, Penicillium, and Fusarium, which are responsible for producing some of the most concerning mycotoxins.
Types of Mycotoxins Found in Buckwheat
Research has specifically identified the presence of certain mycotoxins in buckwheat, which pose potential health risks. The most common ones include:
- Aflatoxin B1 (AFB1): A potent hepatocarcinogen, AFB1 has been found in buckwheat, particularly at high levels in the outer hulls of raw, unsteamed grain. A study found high concentrations of AFB1 in raw hulls, emphasizing the importance of processing.
- Ochratoxin A (OTA): This nephrotoxic mycotoxin has been found in buckwheat flour and noodles, albeit typically at lower levels than in cereals. OTA is known to be relatively heat-stable.
- Trichothecenes (e.g., T-2 toxin, DON): These toxins, particularly T-2 and Deoxynivalenol (DON), have been reported in buckwheat samples. The T-2 toxin, like AFB1, was found in high concentrations in raw hulls.
How Processing and Storage Mitigate Risk
Proper post-harvest handling and industrial processing are the most effective measures for controlling mycotoxin levels in buckwheat products. The dehulling process, for instance, is crucial because the outer hull can accumulate significantly higher mycotoxin levels than the inner groat. Furthermore, thermal treatment like steaming plays a vital role in decontaminating the grain.
Critical Steps for Reducing Mycotoxin Contamination
- Thermal Treatment: Steaming is a standard processing method that significantly reduces mycotoxin levels. A study showed that raw buckwheat groats and hulls had several times more AFB1 contamination compared to steamed ones.
- Dehulling: The process of removing the hull from the buckwheat groat is key, as the hulls can act as a protective barrier and concentrate mycotoxins. The removal of these hulls prevents highly contaminated material from reaching the edible portion.
- Proper Storage: Like all grains, buckwheat should be stored in a cool, dry place free from insects and pests. High moisture content during storage is a primary factor in promoting mold growth and mycotoxin production.
Raw vs. Steamed Buckwheat: A Comparison
| Feature | Raw Buckwheat (unsteamed) | Steamed Buckwheat (Kasha) |
|---|---|---|
| Mycotoxin Levels | Significantly higher contamination risk, especially in the hulls. | Substantially lower mycotoxin levels, often at trace or non-detectable concentrations in the groats. |
| Fungal Contamination | Higher overall levels of mould fungi, as thermal treatment is absent. | Lower mycological contamination due to the heat treatment. |
| Appearance | Lighter in colour and milder flavour. | Brownish colour with a toasted, nutty flavour due to the steaming process. |
| Phenolic Compounds | Higher total phenolic content in groats compared to steamed groats, though overall mycotoxin risk is greater. | Lower levels of total phenolics in groats, but a more favorable ratio of beneficial compounds to mycotoxins in the final food product. |
Minimizing Your Exposure to Mycotoxins in Buckwheat
For consumers, ensuring a low risk of mycotoxin exposure involves several practical steps, from purchasing to preparation.
- Choose Reputable Brands: Buy buckwheat from established companies with good quality control standards. Most commercial products undergo some form of heat treatment or strict quality assurance checks to minimize mycotoxins.
- Opt for Steamed Groats: Whenever possible, choose pre-steamed buckwheat groats (kasha) over raw ones, as steaming is a known method for reducing contamination.
- Store Properly: Once purchased, store buckwheat products in a cool, dry, and sealed container. This prevents moisture buildup, which can encourage mould growth.
- Inspect for Signs of Mould: Before cooking, visually inspect buckwheat for any signs of discolouration, mould, or shrivelled grains and discard any that look questionable.
- Eat a Varied Diet: Following a diverse diet is a good practice for reducing exposure to any single type of contaminant. This also improves overall nutrition.
Conclusion
Buckwheat is a healthy, gluten-free pseudocereal, but it is not immune to mycotoxin contamination. However, classifying it as 'high' in mycotoxins is an oversimplification, as the levels are heavily influenced by cultivation, storage, and, most importantly, processing methods. Steaming and dehulling are highly effective at reducing contamination, especially of the most concerning toxins like aflatoxins. By purchasing high-quality, processed buckwheat and storing it properly, consumers can significantly mitigate the risk and safely enjoy its many health benefits. Ultimately, an informed approach to purchasing and handling buckwheat is the best defense against mycotoxin exposure. To learn more about mycotoxin risks in food, you can consult the World Health Organization's factsheet on the topic.
