Mycotoxins are toxic compounds produced by certain moulds that grow on crops in the field or during storage. Aflatoxins, produced mainly by Aspergillus flavus and Aspergillus parasiticus, are the best known, and nuts, spices, cereals, dried fruit and milk are among the foods most often affected.
They matter because they are invisible, largely survive cooking and processing, and can cause long-term harm at low levels. Nut and spice consignments are routinely checked for aflatoxins, and a failed result can mean a rejected shipment and a damaged customer relationship.
The main mycotoxins in food
Aflatoxins
Aflatoxins B1, B2, G1 and G2 occur in peanuts, tree nuts such as pistachios and almonds, maize, spices such as chilli, and dried figs. Aflatoxin B1 is generally the most toxic and the most common.
Aflatoxin M1 is a metabolite of B1 that appears in the milk of animals fed contaminated feed. Controlling aflatoxin in animal feed therefore protects milk and dairy products.
Ochratoxin A
Produced by some Aspergillus and Penicillium species and found in cereals, coffee, cocoa, dried vine fruit, wine and spices. The kidney is its main target organ.
Patulin
Produced mainly by Penicillium expansum on damaged or rotting fruit, especially apples. The main concern is apple juice and apple products made from poorly sorted fruit.
Fumonisins and deoxynivalenol (DON)
Both come from Fusarium species. Fumonisins occur mainly in maize and maize products. DON, also called vomitoxin, occurs in wheat, barley, oats and maize, often after wet weather around flowering and harvest, and can cause vomiting and gastrointestinal effects at high exposure.
Health effects
The International Agency for Research on Cancer (IARC) classifies aflatoxins, including aflatoxin B1, in Group 1, carcinogenic to humans, with the liver as the main target. The risk is higher in people with chronic hepatitis B infection. Very high exposure can cause acute aflatoxicosis, which can be fatal.
IARC classifies ochratoxin A and fumonisin B1 in Group 2B, possibly carcinogenic to humans. Because many effects follow long-term exposure, regulators set maximum levels and expect exposure to be kept as low as reasonably achievable.
Mycotoxins, foods and controls
| Mycotoxin | Main source | Typical foods | Key controls |
|---|---|---|---|
| Aflatoxins B1, B2, G1, G2 | Aspergillus flavus, A. parasiticus | Peanuts, tree nuts, maize, spices, dried figs | Rapid drying, cool dry storage, sorting, supplier control, lot testing |
| Aflatoxin M1 | Metabolite of B1 in animals | Milk and dairy products | Aflatoxin control in animal feed, milk testing |
| Ochratoxin A | Aspergillus and Penicillium species | Cereals, coffee, cocoa, dried vine fruit, spices | Good drying, humidity control in storage, specifications |
| Patulin | Penicillium expansum | Apples and apple juice | Removing rotten fruit before pressing, cold storage of fruit |
| Fumonisins | Fusarium species | Maize and maize products | Good agricultural practice, cleaning and sorting, testing |
| DON | Fusarium species | Wheat, barley, oats, maize | Agricultural practice, grain cleaning, supplier testing |
How to control mycotoxins
Once formed, mycotoxins cannot be reliably removed, and normal cooking does not destroy most of them. Codex codes of practice for cereals, peanuts and tree nuts set out preventive good practice.
- At harvest: good agricultural practice, insect control, minimal damage and timely harvest.
- Drying: dry crops quickly to a safe moisture level, because mould grows in damp produce.
- Storage and transport: keep produce cool and dry, control pests, and prevent condensation in containers, a real risk when shipping into hot, humid climates such as the Gulf.
- Sorting: remove damaged, discoloured or mouldy kernels by hand or with optical sorters, since contamination often concentrates in a small fraction of kernels.
- Supplier control: approve suppliers on their drying, storage and testing controls, require a COA per lot, and verify it; see supplier approval in food safety.
Sampling and testing
Why sampling matters
Aflatoxin contamination is highly uneven. In a lot of nuts, a very small number of kernels can carry most of the toxin while the rest are clean. A small sample can miss them, or catch one and overstate the lot.
Recognised sampling plans therefore take many incremental samples from across the lot, combine them into a large aggregate sample, grind or slurry the whole of it, and then take the test portion. Sampling usually contributes more uncertainty than the analysis itself.
Follow the sampling method your regulator or customer requires; Codex and the EU both publish sampling plans for aflatoxins in certain foods.
Testing methods
- HPLC with fluorescence detection: a widely used confirmatory method, often after immunoaffinity column clean-up.
- LC-MS/MS: detects and confirms several mycotoxins in one run.
- ELISA: a plate-based immunoassay suited to screening many samples; see our ELISA troubleshooting guide.
- Lateral flow strips and rapid kits: quick screening at receipt, with results near or above a limit confirmed by a laboratory method.
Where results support release or regulatory decisions, use a laboratory accredited to ISO/IEC 17025:2017 for the relevant mycotoxin and matrix.
Regulatory limits
Maximum levels exist for mycotoxins in many foods. Key references include:
- Codex: General Standard for Contaminants and Toxins in Food and Feed (CXS 193-1995).
- GCC: GSO standards on maximum levels of mycotoxins and contaminants, applied by national authorities such as the SFDA and UAE regulators.
- EU: Regulation (EU) 2023/915 on maximum levels for certain contaminants in food.
- India: Food Safety and Standards (Contaminants, Toxins and Residues) Regulations, 2011, as amended.
Limits differ by mycotoxin, food, market, and whether a product is ready to eat or destined for further sorting or processing. They are revised from time to time, so check the current text for your product and destination before setting specifications.
Worked example: a UAE pistachio importer
A UAE importer brings in in-shell pistachios from several origins, stores them in a warehouse and supplies roasters and retailers across the GCC. Every lot arrives with a supplier COA within limits. When a customer's test finds a result near its limit, QA reviews the controls:
- COA review: the COAs come from suppliers' in-house laboratories and do not state the sampling method or sample size.
- Own sampling: the importer adopts a sampling plan based on lot size, with incremental samples from across all bags, the full aggregate sample ground, and testing by an ISO/IEC 17025 accredited laboratory using HPLC.
- Rapid screening: lateral flow strips at receipt help prioritise lots for laboratory testing, but are not used to release them.
- Storage: warehouse temperature and humidity logging begins, and pest control is reviewed.
- Suppliers: COAs must now come from accredited laboratories and state the sampling method. One supplier with repeated high results is suspended pending a review of its drying and sorting.
A later lot tests above the importer's limit. It is held, segregated and the supplier informed. Blending it with compliant stock to dilute the result is not an option, as regulators generally prohibit this, so the lot is returned to the supplier.
Common mistakes
- Accepting COAs without knowing how the sample was taken.
- Taking small grab samples from the top of a few bags.
- Treating rapid strip results as final release results.
- Storing nuts and spices in warm, humid warehouses without monitoring.
- Assuming roasting or cooking removes aflatoxins.
- Blending contaminated lots with clean ones.
- Ignoring aflatoxin M1 risk in dairy supply chains.
Key takeaway: Mycotoxins are prevented, not cooked out. Control drying, storage and suppliers, sample in a way that reflects how unevenly aflatoxin is spread, confirm screening results in an accredited laboratory, and check limits against the current regulations for each market.
Frequently Asked Questions
What is aflatoxin and where is it found?
Aflatoxin is a group of toxins produced mainly by Aspergillus flavus and Aspergillus parasiticus moulds. It is found most often in peanuts, tree nuts such as pistachios, maize, spices and dried figs, especially when crops are damaged or dried and stored poorly. Aflatoxin M1 can appear in milk.
Does roasting or cooking destroy aflatoxin?
Not reliably. Aflatoxins are heat stable, and normal cooking, boiling or roasting reduces them only partly, depending on temperature, time and moisture. Roasting cannot be relied on to bring a contaminated lot within limits. Prevention, sorting and testing before processing are the effective controls.
Is aflatoxin a carcinogen?
Yes. The International Agency for Research on Cancer classifies aflatoxins, including aflatoxin B1, in Group 1, carcinogenic to humans. The main target is the liver, and the risk is higher in people with chronic hepatitis B infection. This is why regulators set strict maximum levels.
Why is sampling so important for aflatoxin testing?
Aflatoxin is spread very unevenly, with most of the toxin often in a few kernels. A small or poorly taken sample can miss contamination or overstate it. Recognised plans take many incremental samples, combine and grind a large aggregate, and then test a portion, so the result represents the lot.
Next steps
Advanced Food Safety Management & Compliance covers supplier assurance and chemical hazards, and the Highfield Level 3 International Award in HACCP builds hazard analysis skills.
For related reading, see our guides to supplier approval in food safety, food traceability and recall readiness and measurement uncertainty in testing labs. Not sure which course fits your role? Speak to a counsellor.
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