What are the mycotoxins in figs?

Figs, particularly dried varieties, are notably susceptible to mold contamination, which can produce toxic secondary metabolites. These toxic compounds, known as mycotoxins, can pose significant health risks if consumed and are a major concern in global food safety.

Quick Summary

Dried figs are prone to contamination by mycotoxins, most notably carcinogenic aflatoxins and potentially carcinogenic ochratoxin A, produced by certain molds during drying and storage.

Key Points

• Aflatoxins are Carcinogenic: The most significant mycotoxins in figs are aflatoxins, particularly B1, which are classified as highly carcinogenic.

• Ochratoxin A Affects Kidneys: Another primary mycotoxin is ochratoxin A, which poses risks to kidney health and is a possible human carcinogen.

• Drying Increases Risk: Dried figs are most susceptible to mold and mycotoxin contamination during the sun-drying phase and subsequent storage.

• Preventive Measures are Crucial: Proper harvesting (daily collection), controlled drying, and effective storage at low temperatures are critical for prevention.

• Sorting and Inspection are Key: Producers use UV light to detect fluorescence associated with aflatoxins, while consumers should visually inspect figs for any signs of mold or discoloration.

• Other Mycotoxins Can Occur: Besides aflatoxins and OTA, other metabolites like fumonisins, cyclopiazonic acid, and alternaria toxins have been found in figs.

What Mycotoxins Are Found in Figs?

Mycotoxins are naturally occurring toxins produced by certain molds and can contaminate agricultural products, including figs, especially when conditions are warm and humid. Dried figs are particularly vulnerable due to their drying process, which often involves being left on the tree and ground. Several mycotoxins have been identified in figs, with aflatoxins and ochratoxin A being the most concerning due to their toxicity and frequent occurrence.

Aflatoxins (AFs)

Aflatoxins are potent, genotoxic carcinogens produced primarily by Aspergillus flavus and Aspergillus parasiticus. The most common types found in figs are aflatoxin B1 (AFB1), B2, G1, and G2. AFB1 is the most frequent and most toxic of the group. These molds can infest figs at multiple stages, from ripening on the tree to drying and storage. Research has also surprisingly identified aflatoxin M1 (AFM1), a metabolite of AFB1, naturally occurring in dried figs.

Ochratoxin A (OTA)

Ochratoxin A is another significant mycotoxin in figs, classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen (Group 2B). OTA is produced by various species of Aspergillus and Penicillium, particularly Aspergillus carbonarius. It is known for its adverse effects on the kidneys and has been linked to human kidney disease in some areas. Contamination with OTA can occur during the drying and post-drying stages.

Other Mycotoxins

Beyond the primary culprits, other fungal metabolites have been detected in figs, including:

• Fumonisins (FB1, FB2): Produced by Fusarium species, often associated with fig endosepsis. While more common in corn, they have been found in figs.
• Alternaria Toxins: Such as tenuazonic acid, which has been found in all tested fig samples in some studies, although at variable concentrations.
• Kojic Acid: Also a fungal metabolite, found in significant quantities in some fig samples.
• Cyclopiazonic Acid (CPA): Produced by Aspergillus flavus, and in some cases, is more common in figs than aflatoxins.

Factors Contributing to Mycotoxin Contamination

Mycotoxin contamination in figs is influenced by a range of agricultural and environmental factors throughout the production process.

Agricultural Practices

• Harvesting Technique: The traditional method of allowing figs to over-ripen and drop to the ground before collection increases the risk of mold infection from soil. Daily collection is recommended to minimize soil contact and damage.
• Drying Method: Sun-drying, where figs are exposed to the elements, can create ideal conditions for mold growth, especially in warm, humid weather. Controlled solar drying or artificial drying is more effective at preventing mold.
• Insect Damage: Pests can damage the fruit, creating entry points for mold spores. Effective pest control is a critical prevention step.

Post-Harvest Conditions

• Storage Temperature and Humidity: Molds thrive in warm, moist conditions. Storing figs at mild temperatures or in high humidity can promote mycotoxin production. Storage at low temperatures (<10°C) is recommended.
• Water Activity: Even after drying, if the water activity ($a_w$) is not low enough (below 0.60), xerophilic molds like Aspergillus flavus can still produce toxins.
• Cross-Contamination: Contamination can spread from one fruit to another. Good manufacturing practices, including clean equipment and storage facilities, are essential.

Mycotoxin Comparison in Figs

Feature	Aflatoxins (AFs)	Ochratoxin A (OTA)
Primary Mold Producers	Aspergillus flavus, A. parasiticus	Aspergillus carbonarius, A. ochraceus, Penicillium
Primary Health Concern	Genotoxic and carcinogenic (liver cancer)	Possible human carcinogen (kidney disease)
Contamination Stage	All stages, especially ripening and drying	Drying and storage stages
Detection	Often associated with bright greenish-yellow fluorescence (BGYF) under UV light	Requires laboratory analysis, not visually obvious
Regulation	Widely regulated with very low maximum limits (EU, Codex)	Regulated in many countries; EU has specific limits for figs

Prevention and Control Measures

For both producers and consumers, minimizing the risk of mycotoxin exposure from figs is crucial. Producers employ stringent measures, and consumers can take simple steps to ensure safety.

For Producers:

• Harvesting: Collect figs daily to prevent prolonged contact with contaminated soil.
• Drying: Use controlled drying methods, like solar dryers, rather than uncontrolled sun-drying. Optimal drying temperatures, such as those near 37°C, inhibit mold growth.
• Sorting: Implement sorting under UV light to identify and remove figs showing the characteristic fluorescence of aflatoxin contamination.
• Storage: Store figs at cold temperatures (<10°C) with low humidity and practice effective pest control.

For Consumers:

• Inspect Visuals: Check dried figs for any signs of mold, discoloration, or shriveling and discard them if they look unusual.
• Source Wisely: Purchase figs from reputable suppliers who follow strict food safety protocols and test for mycotoxins.
• Proper Storage: Store dried figs in a cool, dry place, ideally refrigerated, to prevent mold development.
• Buy Fresh: For the lowest risk, opt for fresh figs when in season, as contamination primarily occurs during the drying process.

Conclusion

Mycotoxins, particularly aflatoxins and ochratoxin A, are a documented risk in figs, especially dried varieties, stemming from mold contamination during ripening, drying, and storage. While their presence is a serious food safety concern, robust control measures exist at both the production and consumer level to minimize exposure. Consumers should remain vigilant, inspecting figs for any signs of mold and storing them properly, while the industry continues to implement strict monitoring and prevention protocols to ensure the safety of this popular dried fruit. Continued awareness and adherence to safety guidelines are the best defense against mycotoxin contamination in figs. For further information on food safety standards, consult the World Health Organization (WHO) fact sheets on mycotoxins.

Frequently Asked Questions

What are mycotoxins?

Mycotoxins are toxic chemical compounds naturally produced by certain types of molds (fungi) that grow on various crops, including fruits like figs.

Are mycotoxins found only in dried figs?

Mycotoxin contamination is primarily a concern with dried figs because the molds flourish under the warm, humid conditions during the drying process and can continue to grow if improperly stored.

How can I tell if a fig is contaminated with mycotoxins?

It is often not possible to detect mycotoxin contamination by smell or appearance alone. Some contaminated figs might show visible mold or discoloration, but mycotoxins can be present even without visible signs.

Can cooking or heating destroy mycotoxins in figs?

No, most mycotoxins, including aflatoxins, are heat-stable compounds and are not destroyed by typical cooking or heat-processing methods.

What are aflatoxins and why are they dangerous?

Aflatoxins are a group of highly toxic mycotoxins produced by Aspergillus molds. They are potent carcinogens that can cause liver damage and increase the risk of cancer in humans and animals.

What are the common sources of mold contamination in figs?

Molds can infest figs in the orchard, from soil contact after falling from the tree, or during improper storage due to high humidity and temperature.

What can consumers do to reduce mycotoxin exposure from figs?

Consumers can minimize risk by visually inspecting figs for mold or discoloration, purchasing from reputable brands that test their products, and storing dried figs in a cool, dry, or refrigerated environment.