Anomalous aflatoxin B1recoveries from whole peanuts and brazil nuts measured by enzyme?linked immunosorbent assay

Aflatoxin B 1 extraction solvent (acetonitrile?water, 1:1) was shown to be acceptable when performing an ELISA using a dilution of 1 in 20 of nut extracts in assay buffer in order to prevent reductions in assay sensitivity due to nut matrix interferences. An extraction period of 30 min using acetonitrile?water (1:1) was shown to be efficient for the removal of aflatoxin B 1 from peanuts. The extractions were performed immediately after spiking. This dilution was used when analyzing both raw and roasted peanuts, which are finely ground, whole without testa, or only the testa (for this last, only roasted samples were studied). A significant reduction in aflatoxin B 1 recoveries was observed when samples were left to stand overnight after spiking. This suggests that either the aflatoxin B 1 molecule establishes strong bonds with some of the components of the peanut surface, or that substance(s) (non?enzymic) existing at this surface will react with the aflatoxin B 1 molecule, causing it to break down, or modify it to give products that cannot be recognized using the ELISA procedure.