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Category: Applied and Industrial Microbiology; Food Microbiology
Toxigenic Aspergillus Species, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815912/9781555814076_Chap24-1.gif /docserver/preview/fulltext/10.1128/9781555815912/9781555814076_Chap24-2.gifAbstract:
Aspergillus species occur in foods as spoilage or biodeterioration fungi. The most important toxigenic Aspergillus species in foods are the aflatoxigenic molds, A. flavus and A. parasiticus, along with a recently described but much less common species, A. nomius, all of which are classified in Aspergillus section Flavi. The most effective medium for rapid detection of aflatoxigenic molds is A. flavus and parasiticus agar, a medium formulated specifically for this purpose. The combination of characteristics most useful in differentiation among the three aflatoxigenic species is summarized. A. flavus is widely distributed in nature, but A. parasiticus is probably less widespread, determination of the actual extent of its occurrence being complicated by the tendency for both species to be reported indiscriminately as A. flavus. Aflatoxins are one of the few mycotoxins covered by legislation. A. ochraceus is the most commonly occurring species in what was known as the A. ochraceus group by Raper and Fennell, now correctly known as Aspergillus section Circumdati. Aspergillus clavatus is the most common member of the section Clavati, subgenus Clavati, and is easily recognizable by its large, blue-green clavate (club-shaped) heads. The genus Eurotium is an ascomycete genus characterized by the formation of bright yellow cleistothecia, often enmeshed in yellow, orange, or red hyphae, overlayed by the gray-green (glaucous) Aspergillus heads of the anamorphic state. Aspergillus is one of the most important genera in the spoilage of foods and animal feeds, particularly in warm-temperate climates and the tropics.
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Aflatoxigenic fungi. (A) A. flavus head (magnification, ×215); (B) A. flavus conidia (magnification, ×1,350); (C) young A. parasiticus heads (magnification, ×215); (D) A. parasiticus conidia (magnification, ×1,350).
Some common mycotoxigenic Aspergillus species. (A) A. ochraceus (magnification, ×540); (B) A. versicolor (magnification, ×540); (C) A. fumigatus (magnification, ×540); (D) A. terreus (magnification, ×540); (E) A. clavatus (magnification, ×215).
Significant mycotoxins produced by Aspergillus species and their toxic effects
Distinguishing features of A. flavus, A. parasiticus, and A. nomius