Temperature aflatoxin contamination

Soil populations and aflatoxin contamination are influenced by weather patterns, with hot dry soils favoring the Aspergillus section Flavi. In terms of geographic location, A. flavus incidence is correlated with high minimum temperatures and inversely correlated to latitude. For example, corn ears that develop at temperatures of 28 to 32°C are far more likely to be contaminated by aflatoxin than ears grown later in the season at lower temperatures. However, late planting is not economically feasible due to lower crop yields. Besides hot dry weather, the level of insect and rodent activity in an area may also substantially favor colonization and aflatoxin production. Plant fertility, density, and disease also play roles in the level of aflatoxin contamination. 

Aflatoxins occur both in food crops in the field prior to harvest, and in improperly stored food where mould species have found an opportunity to grow. Fungal growth and aflatoxin contamination are a consequence of an interaction between the mould, the host organic material (i.e. crop, foodstuff) and the environment. The appropriate combination of these factors determines the degree of the colonisation of the substrate, and the type and amoimt of aflatoxin produced. Humidity, temperature and insect damage of the host substrate are major determining environmental factors in mould infestation and toxin production. 

Most data on the relation of temperature to aflatoxin formation have been obtained with A. parasiticus. Aflatoxin contamination of cottonseed by A. flavus in the field occurs primarily in low-altitude areas of Arizona and the Imperial Valley of California and not in the hot and humid Southeastern States. Chronic field contamination of cottonseed apparently requires daily mean temperature of 34 C or above (T.E. Russell, personal communication). The significant difference between Arizona and the Southeast cotton areas is the high night temperatures of 32-34 C in Arizona. 

Postharvest approaches include control of moisture and temperature and proper ventilation. Treatment of contaminated corn with 2% ammonia reduces aflatoxin levels (Park et al., 1988), however this treatment changes the nutritional value of the seed and causes an ammonia odor and a change in color. Ammoniation is not an FDA-approved detoxifying procedure for crops intended for interstate commerce - it can be used only for crops to be used within the confines of a farm. Furthermore, ammoniation is a hazardous procedure for those conducting treatment. 

Certain types of molds can produce mycotoxin. A. flavus and A. parasiticus, under favorable conditions of temperature and humidity, can produce aflatoxins. Produces that are commonly contaminated with aflatoxins are groundnut, maize, chili, spices, and cottonseed (Cotty and Jaime-Garcia, 2007 Kumar et al., 2008). Mycotoxins can also occur in milk and milk products as a result of animals consuming mycotoxin-contaminated feed (Moss, 2002 Cotty and Jaime-Garcia, 2007). P. expansum, causing blue mold rot, can produce toxin called patulin (Barkai-Golan and Paster, 2008 Kumar et al., 2008). 

Heat treatment of contaminated materials decreases mycotoxin concentrations in many cases. Aflatoxins are especially thermostable and a significant decrease in their content occurs at temperatures of about 200 °C. Ergot alkaloids and zearalenone are also very stable at high temperatures. 

Venezuela is a tropical country with high relative humidity and temperature making grains very susceptible to insect attack and mold contamination. This study was designed to provide preliminary information of aflatoxin occurrence on corn and corn flour, and the incidence of Aspergillus flavus or parasiticus contamination. 

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