Volatile organic compounds associated with postharvest fungi detected in stored wheat grain

Abstract

Stored wheat grain from across Australia was tested for the presence of postharvest fungi by measuring the production of volatile organic compounds (VOCs). Headspace analysis combined with gas chromatography flame ionization detection (GC/FID) and gas chromatography-mass spectrometry (GC-MS) was used to detect fungi in the grain, based on identification of peaks associated with species such as Alternaria alternata and A. infectoria. A total of 57 possible compounds were detected by GC/FID. Grain from Queensland, Victoria and New South Wales produced less VOCs compared to grain from South Australia and Western Australia. These compounds appeared at both the early and later stages of fungal growth. For example, A. alternata produced volatiles after two days that were only produced by A. infectoria after seven days. Gamma-irradiated grain (controls) did not produce these VOCs. A further analysis of the 57 VOCs by GC–MS identified three VOCs: Cyclooctasiloxane, hexadecamethyl-(CAS 556–68-3) produced by A. alternata, and Pentadecane (CAS 629–62-9) produced by A. infectora. We conclude that fungal VOCs may be useful for early detection of postharvest fungi in grain, prior to visual symptoms occurring.