Ochratoxin A (OTA) is a naturally occurring mycotoxin produced by several species of the genera Aspergillus (primarily A. ochraceus and A. carbonarius) and Penicillium (primarily P. verrucosum). It is one of the most widespread food-contaminating mycotoxins in Europe, classified by the International Agency for Research on Cancer (IARC) as a Group 2B possible human carcinogen, with nephrotoxic (kidney-damaging), immunotoxic, and teratogenic properties.
OTA forms on a wide variety of commodities during storage or drying when temperature and humidity conditions are suboptimal. Aspergillus species are predominantly responsible in warm, tropical climates, while Penicillium verrucosum is the primary producer in cooler, temperate European conditions. Key commodities at risk include cereals (especially wheat, barley, and rye), dried vine fruits (raisins, currants, sultanas), coffee (especially green and roasted), cocoa, wine and grape juice, dried fruits, spices (especially chili and paprika), and licorice products.
OTA is chemically stable at high temperatures and is not significantly reduced by normal food processing. It accumulates in kidney tissue due to its long biological half-life in humans (approximately 35 days). Monitoring and routine mycotoxin screening are the primary tools for compliance verification under EU food safety regulations.
Analytical Methods
- HPLC-FLD (High-Performance Liquid Chromatography with Fluorescence Detection) — Primary analytical method for OTA in food and wine. OTA exhibits strong native fluorescence, making HPLC-FLD particularly suitable (excitation 330 nm, emission 460 nm). Combined with immunoaffinity column (IAC) or solid-phase extraction (SPE) clean-up. Reference method per Commission Regulation (EC) No 401/2006.
- LC-MS/MS (Liquid Chromatography-Tandem Mass Spectrometry) — Confirmatory multi-mycotoxin method. Enables simultaneous determination of OTA alongside aflatoxins, DON, and other regulated mycotoxins from a single sample extraction, offering high specificity and low detection limits.
- ELISA (Enzyme-Linked Immunosorbent Assay) — Rapid immunochemical screening suitable for high-volume testing of wine, cereals, and coffee. Commercially available with detection limits suitable for EU maximum level compliance. Confirmed positive results require HPLC-FLD or LC-MS/MS.
- Immunoaffinity Column (IAC) Clean-up — Specific OTA antibody-based columns used to selectively extract and concentrate OTA from complex matrices (wine, coffee, spices) prior to HPLC-FLD or LC-MS/MS analysis, significantly improving method sensitivity and selectivity.
EU Regulatory Framework
Maximum levels for ochratoxin A (OTA) in food are set by Regulation (EU) 2023/915 (Annex I, Section 1.3), significantly updated by Regulation (EU) 2022/1370 (effective 1 January 2023). Selected maximum levels:
| Food product | OTA maximum level (µg/kg) |
|---|---|
| Dried currants, raisins, sultanas, and figs | 8.0 |
| Other dried fruit | 2.0 |
| Roasted coffee | 3.0 |
| Instant (soluble) coffee | 5.0 |
| Cocoa powder and chocolate products | 3.0 |
| Wine and grape juice | 2.0 |
| Bakery products, cereal snacks, breakfast cereals | 2.0–4.0* |
| Other cereals and processed cereal products | 3.0 |
| Sunflower, pumpkin, hemp seeds, soybeans, pistachios | 5.0 |
| Dried chili, cayenne pepper, paprika | 20.0 |
| Other dried spices | 15.0 |
| Dried herbs | 10.0 |
| Licorice confectionery (≥97% licorice extract) | 50.0 |
| Other licorice confectionery | 10.0 |
| Cereal-based foods for infants and young children | 0.5 |
* The 4.0 µg/kg limit applies to products containing at least 20% dried vine fruit or figs; 3.0 µg/kg for products containing oilseeds, nuts, or dried fruit; 2.0 µg/kg for other products.
The EFSA Tolerable Weekly Intake (TWI) for OTA is 120 ng/kg body weight per week. Sampling procedures are governed by Commission Regulation (EC) No 401/2006.
Frequently Asked Questions
What is ochratoxin A and why is it a food safety concern?
Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium fungi, classified by IARC as a Group 2B possible human carcinogen. Its primary toxicological concern is nephrotoxicity — it accumulates in kidney tissue with a biological half-life of approximately 35 days in humans, causing progressive kidney damage with chronic exposure. OTA is also immunotoxic and teratogenic. It is widespread in European cereals, dried fruits, coffee, wine, spices, and cocoa.
Which foods have the highest ochratoxin A limits in the EU?
Dried spices (chili, cayenne, paprika) have the highest EU maximum level at 20.0 µg/kg, reflecting their naturally higher contamination potential. Licorice products can contain up to 50.0 µg/kg (products with ≥97% licorice extract). Dried vine fruits (raisins, currants, sultanas) are limited to 8.0 µg/kg, while wine, coffee, and cereals must not exceed 2.0–5.0 µg/kg depending on the product type. The strictest limit (0.5 µg/kg) applies to cereal-based infant foods.
Can ochratoxin A be destroyed by roasting or cooking?
OTA is heat-stable and is not fully eliminated by normal cooking or roasting. Coffee roasting reduces OTA content by approximately 40–80% compared to green coffee beans, but does not eliminate it entirely. Baking bread reduces OTA in grain products to some extent. Because processing cannot guarantee removal of excess OTA, raw material quality control through testing is essential before processing begins.
What analytical methods are used to detect ochratoxin A?
HPLC with fluorescence detection (HPLC-FLD), combined with immunoaffinity column (IAC) clean-up, is the EU reference method for OTA per Commission Regulation (EC) No 401/2006. This method exploits OTA’s strong native fluorescence. LC-MS/MS is used for confirmatory multi-mycotoxin analysis covering OTA alongside aflatoxins, DON, and other regulated compounds simultaneously. ELISA enables rapid high-throughput screening of wine, cereals, and coffee.
What is the EFSA Tolerable Weekly Intake for ochratoxin A?
The European Food Safety Authority (EFSA) has established a Tolerable Weekly Intake (TWI) of 120 nanograms per kilogram of body weight per week (120 ng/kg bw/week) for ochratoxin A, based on a benchmark dose approach for nephrotoxic effects in pigs. Monitoring data indicate that dietary exposure from cereals, wine, and dried fruits can approach or exceed this TWI in certain population groups, particularly children and high consumers, underpinning the strict EU maximum levels.