The moulds and mycotoxins that are considered to be of major public health and economic significance worldwide are listed in the table below (FAO, Food and Nutrition Paper 73 [www]).
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Aflatoxins
Aspergillus flavus and Aspergillus parasiticus are the two main sources of aflatoxin contamination during growth, or during post-harvest handling and storage of a wide range of agricultural products. Major foodstuffs commonly associated with aflatoxin contamination include: maize (corn), groundnuts (peanuts), tree nuts, spices, dried fruit, crude vegetable oils, cottonseed and copra. A. flavus and A. parasiticus reportedly grow well at high levels of water activity (around 0.99). Minimum water activity for growth has reported as 0.82 for A. flavus and 0.87 for A. parasiticus. [ i ]
The four main aflatoxins (B1, B2, G1, G2) usually occur together in varying ratios. Aflatoxins M1 and M2 are hydroxylated metabolites of B1 and B2 found in the milk of animals that have ingested contaminated feed. Both acute and chronic adverse effects of aflatoxin intake have been reported. According to the review carried out by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) [.pdf] at its 49th meeting, aflatoxins are among the most mutagenic and carcinogenic substances known, with aflatoxin B1 being the most potent carcinogen of the aflatoxins. The population risk of liver cancer caused by chronic exposure to aflatoxins increases greatly in the presence of hepatitis B infection.
The following Codex Alimentarius Commission [www] Standards and Guidelines pertain specifically to the regulation and control of aflatoxin contamination in foods:
- Aflatoxin M1: Maximum level (Codex STAN 232-2001)
- Maximum Level and Sampling Plan for Total Aflatoxins in Peanuts Intended for Further Processing (CODEX STAN 209-199; Rev. 1-2001)
- Code of Practice for the reduction of aflatoxin B1 in raw materials and supplemental feeding stuffs for milk producing animals (CAC/RCP 45-1997)
- Code of Practice for the Prevention and Reduction of Aflatoxin Contamination in Peanuts (CAC/RCP 55-2004)
T-2 toxin and Deoxynivalenol
T-2 toxin and deoxynivalenol (DON) belong to a group of structurally related compounds known as the 'tricothecenes'. T-2 toxin contamination is commonly found in cereal crops particularly in cases where there is prolonged wet weather during the harvest period. Its production is mainly associated with the mould Fusarium sporotrichiodes. DON is commonly found in a variety of grains, especially wheat, barley, oats, rye and maize and less often in rice and sorghum. DON is the most widely occurring Fusarium mycotoxin, and is produced primarily by Fusarium graminearum, and F. culmorum. F. graminearum grows optimally at a temperature of 25°C at Aw levels above 0.88, while F. culmorum grows optimally at 21°C at Aw levels above 0.87.
An evaluation by JECFA in 2001 resulted in a recommendation for more epidemiological and toxicological studies on these toxins so as to provide a better basis for understanding the health impact of chronic exposure. It is thought that their adverse health effects may include immunotoxicity, hematotoxicity, and reduced growth. DON is also called 'vomitoxin' and is associated with feed refusal, especially in pigs. The 56th meeting of JECFA set a provisional maximum tolerable daily intake (PMTDI) level for DON at 1 µg/kg body weight and for T-2 toxin, the PMTDI was set at 0.6 µg/kg body weight.
The following Codex Alimentarius Commission Guideline pertains to the regulation and control of tricothecene contamination in cereals:
- Code of Practice for the reduction of mycotoxin contamination in cereals including annexes on Ochratoxin A, Zearalenone, Fumonisins and Tricothecenes (CAC/RCP 51-2003 [.pdf])
Zearalenone
Zearalenone is an important mycotoxin in temperate and warm regions. It is an oestrogenic mycotoxin produced by several fungi of the genus Fusarium, including F. graminearum, F. culmorum, F. cerealis, F. equiseti, and F. semitectum. The toxin has been found mainly in maize, but also at lower levels in rice, wheat, barley, malt and soybean. Toxin production reportedly occurs before harvesting, but post-harvest contamination is possible under conditions of poor handling. Pigs are especially sensitive where the symptoms range from missed ovulation to spontaneous abortion.
The chronic adverse health effects of zearalenone are due to its oestrogenic and possibly carcinogenic properties. The 53rd meeting of JECFA set a provisional maximum tolerable daily intake of 0.5 µg/kg of body weight.
The following Codex Alimentarius Commission Guideline pertains to the regulation and control of zearalenone contamination in cereals:
- Code of Practice for the reduction of mycotoxin contamination in cereals including annexes on Ochratoxin A, Zearalenone, Fumonisins and Tricothecenes (CAC/RCP 51-2003 [.pdf])
Fumonisin B1
The fumonisins are a class of mycotoxins that are produced mainly by Fusarium moniliforme (also called F. verticilloides, especially in Europe) and several other Fusarium species. These mycotoxins are a structurally related group of compounds - at least 12 fumonisin analogues have been identified and classified into series A, B, F and P. The B series is the most commonly occuring and the most toxic of the analogues. F. moniliforme is a soil borne organism often associated with maize, which is the food commodity that is most commonly affected by fumonisin contamination. Higher levels of fumonisins are usually found in warmer regions.
The fumonisins are suspected carcinogens and are associated with liver damage. The 56th meeting of JECFA set a provisional maximum tolerable daily intake at 2 µg/kg body weight for fumonisins B1, B2 and B3, alone, or in combination.
The following Codex Alimentarius Commission [www] guideline pertains to the regulation and control of fumonisin contamination in cereals:
- Code of Practice for the reduction of mycotoxin contamination in cereals including annexes on Ochratoxin A, Zearalenone, Fumonisins and Tricothecenes (CAC/RCP 51-2003 [.pdf])
Patulin
Patulin is a mycotoxin produced by many species of mould belonging primarily to the genera Aspergillus, Penicillium and Byssochlamys [= Paecilomyces]. It is particularly associated with the apple rotting fungus, Penicillium expansum. Patulin is found in many fresh and processed fruit and vegetables but even in cereals and fodder. Patulin is water soluble and it is heat and acid stable. Monitoring of patulin in apple juice has revealed widely varying levels of contamination.
Patulin has immunotoxic effects and is suspected to have carcinogenic properties. At its 44th meeting, JECFA set a provisional tolerable daily intake level at 0.4 µg/kg body weight.
The following Codex Alimentarius Commission [www] standards and guidelines pertain to the regulation and control of patulin in foods:
- Code of practice on the prevention and reduction of patulin contamination in apple juice and apple juice ingredients in other beverages (CAC/RCP 50-2003)
- Maximim limits for patulin in apple juice and apple juice ingredients in other beverages (CODEX STAN 235-2003)
Ochratoxin A
Species of only two genera - Penicillium and Aspergillus - are considered to produce OTA. Two species of Penicillium, P. verrucosum and P. nordicum, are now accepted as bona fide OTA )
producers. Members of the Aspergillus ochraceus group, and isolates of A. niger, A. carbonarius and A. terreus are also reported to produce OTA. There are several analogues of OTA, such as ochratoxin B and C, which are all fungal metabolites. However, OTA is the major compound found as a natural contaminant of plant material. OTA contamination is commonly associated with cereals, fresh grapes, dried vine fruit, wine, beer, coffee and cocoa.
P. verrucosum grows only at temperatures below 30°C when the Aw level is above 0.80. It is commonly associated with OTA contamination in cereals produced in temperate zones and is considered to be primarily a problem of post-harvest handling and storage.
OTA is a nephrotoxic, carcinogenic, teratogenic and possibly genotoxic substance. At its 56th meeting, JECFA confirmed a provisional tolerable weekly intake level of 0.1 µg/kg body weight.
The following Codex Alimentarius Commission Guideline pertains to the regulation and control of ochratoxin A contamination in cereals:
- Code of Practice for the reduction of mycotoxin contamination in cereals including annexes on Ochratoxin A, Zearalenone, Fumonisins and Tricothecenes (CAC/RCP 51-2003 [.pdf])
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