Do Sesame Seeds Have Aflatoxins? Understanding the Risk

October 31, 2025 •

4 min read

Yes, studies have confirmed that sesame seeds can and do become contaminated with aflatoxins, a type of toxic mycotoxin produced by certain molds. This contamination occurs most often during improper harvesting, transportation, or storage, especially in hot, humid conditions that favor fungal growth. Understanding these risks is the first step toward minimizing them effectively.

Quick Summary

This article explains how and why sesame seeds can be contaminated with aflatoxins, which are hazardous fungal toxins. It details the conditions that promote mold growth, examines how processing affects toxin levels, and outlines crucial prevention strategies for consumers and producers alike.

Key Points

Aflatoxin Occurrence: Sesame seeds can be contaminated with aflatoxins, a type of mycotoxin produced by mold, primarily Aspergillus flavus and A. parasiticus.
Contamination Factors: High temperature, high moisture, and poor storage practices are the main contributors to aflatoxin contamination in sesame seeds.
Processing Effects: Processing methods like washing and peeling can reduce aflatoxin levels, but roasting may not eliminate them completely, as aflatoxins are heat-resistant.
Prevention Strategies: Prevention is key and involves good agricultural practices, proper drying of seeds, clean storage facilities, and advanced sanitization techniques like RF or UV-C irradiation.
Health Risks: Aflatoxin exposure carries serious health risks, including liver damage and cancer, though regulatory standards aim to minimize consumer risk.
Consumer Action: Consumers should opt for reputable brands, store seeds properly in cool, dry conditions, and stay informed about food safety to reduce personal risk.

What Causes Aflatoxin Contamination in Sesame Seeds?

Aflatoxin contamination is not an inherent property of sesame seeds but is a result of infection by certain mold species, primarily Aspergillus flavus and Aspergillus parasiticus. This fungal growth can happen at multiple stages of the sesame seed value chain.

Environmental Conditions

Fungi that produce aflatoxins thrive in specific environmental conditions. High temperature and high moisture levels are the most critical factors. In many tropical and subtropical regions where sesame is cultivated, these conditions are prevalent, making contamination more likely. Other contributing physical factors include:

Relative humidity: Levels of 85% or higher significantly increase aflatoxin production.
Temperature: The optimum temperature range for aflatoxin production is 25–35°C.
Poor Drying: Inadequate drying of seeds after harvest leaves them susceptible to fungal growth during storage.

Agricultural and Storage Practices

Improper handling and storage are major causes of contamination, particularly during the post-harvest phase.

Harvesting: Physical damage to the seed husks from improper harvesting or insect activity creates entry points for mold spores.
Storage: Poor storage facilities with improper ventilation, damp floors, or exposure to pests can lead to ideal conditions for mold growth. Storing seeds in conditions with high moisture content is a primary risk factor.
Handling: Unhygienic handling practices, such as contaminated equipment or surfaces, can introduce mold spores to the seeds.

Are All Sesame Seeds and Products Contaminated?

No, not all sesame seeds and products are contaminated, and studies show significant variation. Research indicates that contamination levels differ based on the region of origin, agricultural practices, and processing methods. For instance, a study in Iran found that 55% of raw sesame seed samples were contaminated with aflatoxins, while tahini and tahini halva showed lower prevalence, at 45% and 32.5% respectively. This suggests that processing can help reduce but not fully eliminate contamination.

Effect of Processing on Aflatoxin Levels

Various processing methods can impact the final aflatoxin levels in sesame products:

Washing and Peeling: Washing and peeling sesame seeds can reduce aflatoxin levels, as some of the contamination is found on the outer hull.
Roasting: While heat can degrade some aflatoxins, the temperatures typically used for roasting sesame seeds (e.g., 100–150°C) are often insufficient for complete elimination. A study on tahini processing noted that roasting did not fully eradicate aflatoxins. However, some studies show significant reduction, and the effectiveness depends on temperature, time, and moisture content.
Dilution: For products like halva, the addition of ingredients such as sugar can dilute the overall concentration of aflatoxins, even if the source seeds were contaminated.

Mitigating the Risk: Prevention and Control

Controlling aflatoxin contamination requires a multi-pronged approach covering both pre- and post-harvest stages.

Prevention During Cultivation and Harvest

Biological Control: Using atoxigenic strains of Aspergillus can competitively inhibit the growth of toxigenic strains in the field.
Resistant Varieties: Breeding for and planting resistant varieties of crops can minimize the risk of fungal infection.
Timely Harvest: Harvesting crops at the optimal time can reduce field exposure and moisture.

Post-Harvest Management and Storage

Proper Drying: Seeds must be properly dried to a safe moisture level, typically below 12%, immediately after harvest.
Clean Storage: Store seeds in clean, dry, well-ventilated storage facilities. Regular cleaning of storage equipment and bins is essential.
Pest Control: Minimizing insect and rodent activity can prevent damage to seeds and reduce the risk of contamination.
Advanced Sanitization: Technologies like Radio Frequency (RF) can be used for pre-storage sanitization to reduce microbial load and moisture content. UV-C irradiation has also shown promise in reducing fungal growth and aflatoxin levels.

Comparison of Aflatoxin Reduction Methods


Method	Effectiveness	Application Stage	Pros	Cons
Proper Drying	Very High	Post-harvest	Low cost, essential for prevention	Requires proper equipment and monitoring
Biological Control	High	Pre-harvest	Natural, sustainable	Strain adaptability varies, regional availability
Optical Sorting	Variable	Post-processing	Removes heavily contaminated particles	Can be expensive, may not remove all toxins
Roasting	Partial to High	Processing	Reduces some toxins, improves flavor	Often insufficient for complete elimination
RF Technology	High	Post-harvest	Fast, chemical-free	Higher initial equipment cost
UV-C Irradiation	High	Post-harvest	Chemical-free, low cost	Requires careful dosage to avoid quality changes

What are the Health Implications?

Aflatoxins, especially B1, are potent carcinogens primarily affecting the liver. Chronic exposure to low doses or acute exposure to high doses can lead to various health problems. Long-term exposure is linked to liver cirrhosis and hepatocellular carcinoma, while acute exposure can cause severe liver damage, vomiting, abdominal pain, and even death. Although sesame seed contamination may be a potential source of exposure, regulatory bodies worldwide set maximum permissible levels to minimize public health risks.

Conclusion

Do sesame seeds have aflatoxins? The answer is yes, they can be contaminated. The risk is not inherent to the seed but depends heavily on agricultural, processing, and storage conditions. Fortunately, adopting proper prevention and control strategies can significantly minimize this risk. Consumers can protect themselves by purchasing from reputable brands that follow strict food safety guidelines, storing seeds in cool, dry places, and being mindful of product origin. Ultimately, a vigilant approach from producers and informed choices by consumers are key to ensuring the safety and quality of this nutritious food source.

Frequently Asked Questions

Aflatoxin-producing mold may be visible as a fungal growth on the seeds, but the toxins themselves are not visible to the naked eye. A batch of seeds can appear normal while still being contaminated, requiring laboratory testing for detection.

No, traditional roasting methods are often insufficient to completely destroy aflatoxins. While some reduction may occur, the temperatures required for full elimination are much higher than those typically used for roasting food products.

To prevent contamination, store sesame seeds in a cool, dry place in an airtight container. Ensuring the seeds are properly dried to a low moisture content (around 12% or less) before storage is crucial for inhibiting mold growth.

Not necessarily. While organic farming avoids certain chemicals, the susceptibility to mold growth remains, especially if post-harvest handling and storage are not managed properly. Contamination depends more on environmental factors and storage practices than on whether the product is organic.

Yes, products derived from sesame seeds, including sesame oil and tahini, can carry aflatoxins. Reputable processors, however, employ steps like washing, peeling, and testing to minimize contamination in finished products.

Maximum permissible levels of aflatoxins are set by regulatory bodies like the EU and USFDA. These limits vary for different commodities and regions but typically range from 2 to 20 ppb, with stricter limits for products like milk.

Aflatoxin contamination is most prevalent in regions with climates favorable to fungal growth, such as tropical and subtropical areas of Asia and Africa. Factors like poor post-harvest management and storage in these regions contribute to the problem.