Biological Methods General Concepts

Historically, biological assays have played a vital role in the detection and isolation of unidentified fungal metabolites in food and feed. In the classic studies of the early 1960s (156), a duckling bioassay was an instrumental tool in the isolation and purification of aflatoxin from groundnut meal. Since then biological assays have aided in the characterization of most mycotoxins. In general, chemical assays are preferred over biological assays for mycotoxin analysis because they are more rapid, reproducible, and specific. However, chemical analysis cannot be used until the toxin has been chemically characterized, standards purified, and appropriate methodology developed (157).

Before using a bioassay as a routine procedure for monitoring mycotoxins, several factors should be considered

(157). First, the bioassay should be able to respond to a diverse range of mycotoxins. Second, the sensitivity and repeatability of the assay must be acceptable. Third, the cost of the assay should be relatively low. Fourth, the results should be obtained in a short time (preferably less than 24 h). Fifth, blanks should be included to determine if toxic effects occur with solvents or carrier reagents. Finally, the occurrence and frequency of false positives should be minimal to none (157). Bioassays can be classified by the organism used—microorganisms, animals, and plants. Vertebrate animals are the most dependable for detection of vertebrate toxins and they include intact animals, skin tests, and chick embryo assays. Bioassays can be highly specific or general, and the choice of type depends on the application. Excellent reviews on the use of biological assays for screening mycotoxins were written by Yates

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