Ochratoxins are toxic substances (mycotoxins) produced naturally by certain fungi or molds. Ochratoxin A (OA) is the most widespread and concerning contaminant in global food supplies due to its high toxicity. OA is stable, meaning it persists through many common food processing steps, posing a continuous risk to human and animal health. Minimizing exposure requires understanding the toxin’s source, biological impact, and control methods.
Fungal Origin and Primary Contaminated Foods
Ochratoxins are primarily produced by molds from the Aspergillus and Penicillium genera, including species like Aspergillus ochraceus, A. carbonarius, and Penicillium verrucosum. These fungi thrive in high moisture and warm temperatures, often during crop growth, harvesting, or storage.
The distribution is climate-dependent: Penicillium verrucosum is common in temperate regions, while Aspergillus species dominate tropical areas. Contamination usually occurs during post-harvest handling when commodities are not dried quickly or are stored in humid conditions, allowing the mold to proliferate.
Many food commodities are susceptible. Frequently contaminated items include cereals (wheat, barley, oats), coffee beans, cocoa, spices, and dried fruits. OA is also found in grape products (wine, juice) and cured meats, often due to contaminated animal feed.
Biological Effects on Human Health
OA exposure is primarily concerning due to its effect on the kidneys, classifying it as a potent nephrotoxin. Chronic ingestion can lead to kidney damage and is strongly implicated in Balkan Endemic Nephropathy (BEN), a progressive kidney disease found in specific rural areas of the Balkans.
BEN is characterized by chronic, irreversible tubulointerstitial damage in the kidneys. Chronic OA exposure is also associated with an increased incidence of urothelial tumors of the upper urinary tract in BEN-affected regions.
At a molecular level, OA exerts toxic effects by inducing oxidative stress and inhibiting protein synthesis. It also possesses genotoxic properties, causing DNA damage that promotes tumor formation. Based on animal studies, the International Agency for Research on Cancer (IARC) classifies OA as a Group 2B agent (a possible human carcinogen).
Secondary effects include immunosuppression, hepatotoxicity, and potential neurotoxicity. OA has a long biological half-life in humans (around 35 days), allowing the compound to accumulate over time. This slow elimination amplifies the potential for chronic toxicity.
Strategies for Monitoring and Minimizing Exposure
Regulatory bodies establish Maximum Permitted Levels (MPLs) for Ochratoxin A to limit consumer exposure. The European Union sets limits that vary by food matrix, applying stricter standards to vulnerable products like infant foods. Monitoring involves rigorous testing of high-risk imported and domestic goods, such as grains and coffee.
Minimizing contamination starts with preventive agricultural measures and good harvest practices. Rapid and adequate drying of crops immediately after harvest is a primary step, reducing moisture below the level required for fungal growth. Subsequent storage must maintain a cool, dry environment to prevent mold proliferation.
During food processing, several methods reduce the toxin. Simple physical actions like sorting, trimming, and polishing grains remove the most contaminated parts. Thermal processing, such as roasting coffee beans at approximately 250°C, can significantly degrade the toxin, sometimes achieving reductions up to 90%.
Other industrial decontamination techniques involve adsorbents (activated carbon or bentonite clay) that bind to the toxin in liquid products. Chemical treatments, including alkaline hydrolysis and ozone gas application, are also explored for breaking down the OA molecule. Consumers minimize exposure by practicing proper food storage and discarding visibly molded items.