There are a lot of different mould contaminations on food possible. Do you know which moulds can be a problem for human health in your products? And what is the underlying dangerous aspect of the presence of certain moulds for your products? One of the frequent issues with moulds on food is the fact that some of them can produce aflatoxins.
Aflatoxins are mycotoxins produced by certain moulds and can cause serious illness in humans and animals. The four major aflatoxins are Aflatoxin B1, Aflatoxin B2, Aflatoxin G1 and Aflatoxin G2. These toxins are produced mainly by certain strains of Aspergillus flavus and Aspergillus parasiticus and sometimes by Aspergillus nomius. Aflatoxin can cause liver cancer, and can lead to liver and immune-system problems. Aflatoxin B1 is the most commonly found in food and is also the most toxic. Aflatoxin can grow at low moisture levels (approximate minimum Aw 0.82) and over a broad temperature range (13 – 37oC).
Crop related products
How do you know if you have aflatoxins in your product? Between 2013 and 2016 there were on average 300 aflatoxin notifications per year in the Rapid Alert System Food & Feed of the European Union. Most notifications came from nuts, nut products and seeds. Below you see the graph of this data (using a logarithmic scale):
Foods in which aflatoxins commonly are found are corn, nuts, rice, peanuts, cocoa beans, ginger, sorghum, cottonseed, tree nuts, copra, black pepper, figs, dried fruit and nutmeg. Below a picture is shown of mould on corn, which might give rise to aflatoxins.
Aspergillus flavus is commonly associated with a disease of corn known as Aspergillus ear rot. Powdery, grey-green spores may develop on the surface of corn ears, and aflatoxins may be produced by the fungus until the kernel moisture reaches about 15 percent. High temperatures, drought stress, and insect injury may contribute to increased aflatoxin contamination in corn.
Aspergillus flavus and Aspergillus parasiticus may cause a disease of peanuts known as yellow mould, and high levels of aflatoxin contamination may result following relatively high temperatures and moderate humidity. Cottonseed, an important food source for dairy cattle, may become contaminated with aflatoxins if the seed-bearing capsules (bolls) are damaged, followed by high humidity and warm temperatures before or after harvest. Tree nuts such as pistachios and almonds may become contaminated with aflatoxins during injury, such as the splitting of hulls.
Aflatoxin M1, is produced by mammals after consumption of feed (or food) contaminated by Aflatoxin B1. Cows are able to convert Aflatoxin B1 into Aflatoxin M1 and transmit it through their milk. Aflatoxin M1 may be found in milk and dairy products. Although Aflatoxin M1 in milk is, by far, not as hazardous as the parent compound, a limit of 0.5 parts per billion is applied, largely because milk tends to constitute a large part of the diet of infants and children. Milk must be routinely tested for this substance.
Low levels of aflatoxin
In most cases the contamination of food products with aflatoxins is present at low levels. These low levels do usually not cause immediate health effects on humans, but do have a longer term impact when consumed regularly. This is one of the main reasons why aflatoxins are so underestimated.
Aflatoxin contamination has rarely occurred in foods at levels that cause acute aflatoxicosis in humans. Aflatoxin acute and chronic exposures are more likely to occur in developing countries where less strict regulatory limits, poor agricultural practices in food handling and storage, malnutrition, and disease are problems. According to the ‘Bad bug book’ Aflatoxicosis in humans has been reported in many countries, including India, China, Thailand, Ghana, Kenya, Nigeria, Sierra Leone, and Sudan.
How can you prevent aflatoxin in your product? Unfortunately we are not in control of the weather. The accumulation of aflatoxin is dependent upon weather conditions. Before harvest, the risk for the development of aflatoxin is greatest during major droughts. When soil moisture is below normal and temperatures are high, the number of Aspergillus spores in the air increases. These spores infect crops through areas of damage caused by insects, and inclement weather. Once infected, plant stress occurs, the production of aflatoxin is favoured. We do have influence on the storage environment. It is important to storage your product under the right temperature and humidity so the Aspergillus cannot produce aflatoxins.
What do you need to do if you have aflatoxin in your product? Aspergillus often looks greenish to the naked eyes, aflatoxins are odourless, tasteless and colourless. Aflatoxin is stable and heat resistant. It is NOT possible to inactivate aflatoxin by heating your product. It is difficult to eliminate aflatoxin once it is produced. When you have aflatoxin in your product and it is above the maximum level than the only option is to destroy the product.
A lot of countries have maximum levels of aflatoxins laid down in regulations. The Codex Standard 193-1995 mentions the maximum levels of aflatoxins and the sampling plans.
On the website of FAO the worldwide regulations for mycotoxins in food and feed 2003 are mentioned. http://www.fao.org/docrep/007/y5499e/y5499e00.htm
Romerlab has also mentioned on their website the Worldwide Mycotoxin regulations. Please follow the link if you want more information about these regulations. https://www.romerlabs.com/en/knowledge-center/knowledge-library/articles/news/worldwide-mycotoxin-regulations/
Another overview of maximum toxin levels in food for several countries can be found here: http://www.mycotoxins.info/myco_info/consum_regu.html
Detection of aflatoxins – a breakthrough
Until recently the most common ways to detect aflatoxins in your product were the ELISA method, liquid chromatography (LC) with fluorescence detection. For quantification or identification purposes the latter is usually extended with LC/mass spectrometry (MS) or LC/MS-MS.
Last year the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) developed a low cost detection method for aflatoxins on location. This is a breakthrough that will help in the early detection of the presence of aflatoxins in crops already during the harvest.