Detecting Aspergillus parasiticus in cereals by an enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was used for the specific dete ction of Aspergillus parasiticus molds in artificially contaminated corn, r ice, wheat and peanut, and also to detect naturally occurring aflatoxigenic molds in the same form cereals. After inoculation of Aspergillus parasitic us in the cereals, the growth of A. parasiticus was monitored by both plate count and ELISA, and the aflatoxin content was measured. Water activity (a (w)) affected the fungal growth, aflatoxin production and degradation. The higher a(w) level (a(w) = 0.98 vs, a(w) = 0.92) resulted in higher fungal g rowth rates and fungal masses in corn, rice and wheat, and the plate count and ELISA measurements were better correlated, with correlation coefficient s of 0.94, 0.93, 0.96 and 0.86, respectively for corn, rice, wheat, and pea nuts. Aflatoxin was also both produced sooner and degraded more rapidly at a(w) = 0.98. Although standard plate counting techniques detected A. parasi ticus/A. flavus in 5 out of the 40 cereal samples bought from retail stores , ELISA did not give a positive result in any of them. After moisturization and incubation of these commercial samples at 28 degrees C for 29 days, th e incident rates of aflatoxigenic molds increased to 65% and 52% by plate c ount and ELISA, respectively. (C) 1999 Elsevier Science B.V. All rights res erved.