Application of essential oils in maize grain: impact on Aspergillus section Flavi growth parameters and aflatoxin accumulation

The antifungal activity of Pimpinella anisum L. (anise), Pëumus boldus Mol (boldus), Hedeoma multiflora Benth (mountain thyme), Syzygium aromaticum L. (clove), and Lippia turbinate var. integrifolia (griseb) (poleo) essential oils (EOs) against Aspergillus section Flavi was evaluated in sterile maize grain under different water activity (a_w) condition (0.982, 0.955, and 0.90). The effect of EOs added to maize grains on growth rate, lag phase, and aflatoxin B₁ (AFB₁) accumulation of Aspergillus section Flavi were evaluated at different water activity conditions. The five EOs analyzed have been shown to influence lag phase and growth rate. Their efficacy depended mainly on the essential oil concentrations and substrate water activity conditions. All EOs showed significant impact on AFB₁ accumulation. This effect was closely dependent on the water activity, concentration, and incubation periods. Important reduction of AFB₁ accumulation was observed in the majority of EO treatments at 11 days of incubation. Boldus, poleo, and mountain thyme EO completely inhibited AFB₁ at 2000 and 3000 μg g^?1. Inhibition of AFB₁ accumulation was also observed when aflatoxigenic isolates grew with different concentration of EOs during 35 days.