Growth and Aflatoxin B1 biosynthesis rate of model Aspergillus flavus NRRL 3357 exposed to selected infrared wavelengths

Abstract

Aflatoxin B1 (AFB1) is a highly toxic substance produced mainly by Aspergillus spp., which are known to contaminate a wide variety of foods and feeds. The objective of this study was to understand the growth and AFB1 production rate of Aspergillus flavus NRRL 3357 and investigate the impact of different infrared (IR) heat intensities on the growth and aflatoxin-producing potential of A. flavus. Thirty healthy corn kernels were inoculated with 1 × 106 spores/mL of A. flavus spores and incubated at 25 °C. Then, A. flavus plate count, ergosterol, and AFB1 were measured every 24 h. In another experiment, inoculated corn incubated for 24 h was exposed to different IR heat intensities and heating durations. Afterward, the IR-exposed A. flavus were incubated for additional 3 and 6 days (4 and 7 days of incubation in total), and the ergosterol and AFB1 concentrations were measured. For non-IR exposed A. flavus, the highest AFB1 concentration (32.2 μg/g) was observed after 6 days of incubation. Treatment at high IR heat intensities and heating duration resulted in low AFB1 and ergosterol concentrations. However, IR heat treatment at low intensities (e.g., 1.86 kW/m2) for 20 s resulted in high AFB1 and ergosterol concentrations (97.83 and 34.84 μg/g, respectively). The sublethal IR heat intensity may have increased the potential of the exposed A. flavus NRRL 3357 to grow and produce AFB1. The outcome of this study will contribute to and enhance the continual efforts of mitigating AFB1 contamination of economically important grains.