Everything About Aflatoxin
Aflatoxins are poisonous carcinogens and mutagens that are produced by certain molds (Aspergillus flavus and Aspergillus parasiticus) which grow in soil, decaying vegetation, hay, and grains. They are regularly found in improperly stored staple commodities such as cassava, chili peppers, cottonseed, millet, peanuts, rice, sesame seeds, sorghum, sunflower seeds, sweetcorn, tree nuts, wheat, and a variety of spices. When contaminated food is processed, aflatoxins enter the general food supply where they have been found in both pet and human foods, as well as in feed stocks for agricultural animals. Animals fed contaminated food can pass aflatoxin transformation products into eggs, milk products, and meat.
What are Aflatoxins?
Aflatoxins are a member of closely related secondary metabolites produced by some strains of moulds. These are one of the most toxic mycotoxins and are such highly toxic compounds that even low levels of contamination can be dangerous. Different food products, including nuts, cereals, cocoa, dried fruit, spices, pulses, oil seeds, and beans, are contaminated with Aflatoxin. The Pistachio nut is a product with the highest risk for aflatoxin contamination. Since aflatoxin contamination is unpredictable and unavoidable, authorized aflatoxin levels are regulated in many countries worldwide.
“Institute of Standards and Industrial Research of Iran (ISIRI) has set a MTL of 5 and 15 ng/g for AfB1 and total aflatoxins, respectively (ISIRI. 2016). European Commission regulating set limits for AFB1 and total AFs 2 and 4 to 10 ng/g respectively in pistachio. Due to the significant health risks associated with the presence of aflatoxins in foods, it is important to establish a data collection on the occurrence of these toxins in nuts as valuable foods.”
How to prevent Aflatoxin contamination?
A prevention plan should consider different steps from cultivation through harvesting, post harvest handling, drying, post drying storage, processing, post processing storage, transportation and marketing.
Harvesting
- Pistachio trees should be harvested ASAP after maturation to prevent quality loss and reduce problems such as fungal attack and infestation with insects and bugs.
- Signs of harvesting time are: separation of the hull from the shell; drying of kernel and hull, decrease in fruit removal force.
- In hand-picking of younger trees, you should use clean traps to prevent contact of the nuts with litter and soil.
Post harvest handling
- Pistachios should be dried and hulled soon after harvest to reduce shell staining and corrosion to assure safety.
- The nuts should be sorted before cold storage to eliminate imperfect nuts, leaves, twigs and other foreign substances.
Drying
- In the two-stage process, the hulled nuts are first dried for about three hours in a column dryer or a rotating drum dryer (air temperature around 82°C) to reach kernel moisture of 12 to 13 percent. Nuts are then transferred to a flat-bottomed grain bin (second stage) where they continue drying with warm air (temperature less than 49°C) for one to two days to reach a moisture content of 5 to 6 percent.
- In the single-stage process, a self-unloading bin dryer is used at an air temperature of 60° to 66°C. Drying time is eight hours.
Conclusion
Further research is required to explore other ways of preventing mold contamination and aflatoxin production. These could involve prevention of contamination in the field by the use of biological control agents that are pathogenic to Aspergillus flavus, such as fungus or harmless bacteria, and that could serve as ecologically friendly bio-competitors. Experts are investigating a genetically engineered antibody to virus production, which could be executed when conditions are favorable to toxin production.