Aflatoxin

Aflatoxins are mycotoxins produced by fungal species such as Aspergillus flavus, Aspergillus parasiticus, and Aspergillus nomius. These toxins are commonly found in both animal feed and food products consumed by humans. Contamination can occur at all stages from crop cultivation through processing to consumption. Aflatoxins are frequently detected in peanuts, hazelnuts, corn, wheat, rice, cocoa, coffee, dried fruits, milk and dairy products, as well as spices such as red pepper, black pepper, ginger, and turmeric. The presence of aflatoxins varies depending on climatic conditions, regional differences, product type, agricultural practices, and storage conditions.

Chemical and Physical Properties

Aflatoxins are heterocyclic compounds with a difuranocoumarin structure. The main types are AFB1, AFB2, AFG1, AFG2, AFM1, and AFM2. AFB1 and AFB2 emit blue fluorescence under ultraviolet light, while AFG1 and AFG2 emit green fluorescence. AFB1 is the most toxic and most prevalent aflatoxin type. The double bond at the C–8,9 position of the furanofuran ring and the lactone ring attached to the coumarin moiety play a decisive role in the interaction of aflatoxins with DNA and proteins. This structure forms the basis of aflatoxin’s mutagenic, teratogenic, and carcinogenic effects.

Contamination Conditions and Formation Mechanism

Environmental conditions are critical for aflatoxin production. The optimal temperature for the growth of aflatoxigenic fungi is 24–35 °C and the relative humidity must exceed 70%. Water activity (aw) and temperature directly influence toxin production. For example, A. flavus requires an aw of 0.73 for growth and 0.85 for toxin production; moisture content ranges between 8–12% and 17–19%. A. parasiticus can grow at a minimum temperature of 6–8 °C with an optimum range of 25–35 °C. Contamination also depends on the moisture content of the product, drying rate, ambient relative humidity, fungal spore density, plant stress, activity of insects and other pests, microbial competition, and plant species. Research has shown that aflatoxin levels in inoculated crops can increase rapidly within a few days.

Presence in Food and Feed

Aflatoxins are found in many cereal products, especially peanuts, hazelnuts, corn, wheat, and rice. Dried fruits and oilseeds are also at risk. Spices, particularly red pepper, black pepper, ginger, and turmeric, are highly susceptible to aflatoxin contamination. AFM1 can be detected in milk and dairy products 12–24 hours after ingestion of AFB1. AFM1 is resistant to thermal processes such as pasteurization, and processing of milk-based products does not significantly alter aflatoxin levels. The contamination level of products varies according to climate, production, and storage conditions.

Effects on Human and Animal Health

Aflatoxins cause both acute and chronic toxicity in humans. Acute exposure can lead to poisoning potentially fatal, while chronic exposure is associated with liver toxicity, hepatocellular carcinoma, teratogenicity, and mutagenicity. The order of toxic potency is AFB1 > AFG1 > AFB2 > AFG2. AFB1 particularly affects the liver and can enhance toxicity in the presence of conditions such as hepatitis B infection. In children, it is linked to kwashiorkor and can cross the placenta if detected in cord blood. In animals, aflatoxins can cause reduced productivity, decreased weight gain, immunosuppression, and cancer development.

Decontamination and Detoxification Methods

Complete removal of aflatoxins from food is difficult. Decontamination methods are classified as chemical, physical, and biological. Chemical methods include sodium hypochlorite, chlorine dioxide, chlorine gas, inorganic and organic acids, and alkalis (sodium hydroxide, ammonium hydroxide). Physical methods include microwave heating, ozonation, UV irradiation, and γ-irradiation. For example, γ-irradiation can reduce aflatoxin levels in peanuts by 75–100%. In biological methods, lactic acid bacteria and Streptococcus lactis are effective in reducing AFB1 levels. However, most of these methods show limited efficacy and may affect the nutritional value, taste, odor, color, and texture of the food. Prevention of contamination is possible through maintaining hygienic conditions from production to consumption and by inhibiting fungal growth.

Legal Regulations and Traceability

Legal limits for aflatoxins have been established in Türkiye and many other countries. According to the Turkish Food Codex:

• Maximum AFB1: 8 μg/kg; total aflatoxins: 15 μg/kg in peanuts and nuts
• AFB1: 2 μg/kg; total aflatoxins: 4 μg/kg in cereals
• Total aflatoxins: 10 μg/kg in hazelnuts, pistachios, and tree nuts
• AFM1: 0.05 μg/kg in milk and dairy products; 0.025 μg/kg in infant formulas
• AFB1: 0.10 μg/kg in infant complementary foods
• AFB1: 5 μg/kg; total aflatoxins: 10 μg/kg in spices

These regulations ensure traceability from production to consumption and control of contamination. Prohibiting the consumption of foods with high aflatoxin levels is essential for protecting public health and preventing economic losses.

Economic and Social Significance

Aflatoxin contamination causes serious economic losses in agriculture and the food industry, in addition to public health risks. Consumption of foods containing high levels of aflatoxins, particularly in export markets, leads to significant financial losses. Therefore, monitoring foods and animal feed using analytical methods from production to consumption is crucial for preventing contamination and inhibiting aflatoxin formation.