Variability of bright, greenish-yellow fluorescent particles and aflatoxin in ground blends of Zea mays

Developing corn (Zea mays) kernels of single cross B73 X Mo17 grown near Columbia, MO, were inoculated with conidia of Aspergillus flavus or A. parasiticus. After harvest bright greenish-yellow fluorescing (BGYF) kernels were selected under ultraviolet black light (365 nm); they contained 3696 ng/g (A. parasiticus strain NRRL 3145) and 6666 ng/g (A. flavus strain UGA 5337) aflatoxins, respectively. The BGYF-free kernels were obtained from the same hybrid grown in northern Iowa. No BGYF kernels nor aflatoxins were found in 10 assays. To assess the variability in detection of BGYF particles and aflatoxin in ground corn blends, a series was developed by mixing BGYF kernels with BGYF-free kernels in various ratios. In the finely ground samples, standard deviations decreased significantly (P = 0.05) among blends for aflatoxin values in mixtures with higher levels of BGYF particles. Strain 3145 (A. parasiticus) was significantly (P = 0.01) different from strain 5337 (A. flavus) for aflatoxins concentration and the number of grams of BGYF in the blends (r greater than 0.99). The percent fines (passed a 40-mesh screen) in ground, 100% BGYF kernels was significantly (P = 0.01) higher for strain 3145 (A. parasiticus) inoculated samples than for strain 5337 (A. flavus) in spite of equivalent grinding procedures. This observation showed that the relationship between aflatoxin levels determined for a sample and the fraction of BGYF material in the blend was dependent on the fungal-strain source of the BGYF kernels used in the blend.