Changes in volatile compounds emitted by fungal pathogen spoilage of apples during decay

Postharvest diseases in apples are mainly caused by pathogenic fungi. Fungal contamination and decay can change some of the emitted volatile organic compounds (VOCs). In this study, three major pathogens isolated from Fuji apples; Penicillium expansum, Botryosphaeria dothidea, and Alternaria alternata, were inoculated onto disease-free Fuji apples. The VOCs released were analyzed using gas chromatography-mass spectrometry combined with solid-phase microextraction to compare the changes in VOCs according to the decay index and pathogen species. After apples were inoculated with pathogens, ethanol, 3-methylbutan-1-ol, benzaldehyde, styrene, limonene and some ethyl esters constituted the main VOCs emitted during decay. The main volatile compounds according to pathogen species were (E)-hex-2-enal, 1-methoxy-3-methylbenzene, methyl heptanoate, diethyl carbonate, ethyl 2-phenylacetate, propyl octanoate, and ethyl decanoate produced in P. expansum, (E)-hex-3-enyl acetate, 1-methyl-4-propan-2-ylbenzene, 2-phenylethanol, α-terpinene, and α-terpinolene in B. dothidea, and phenylmethanol, 2-ethylhexan-1-ol, and acetophenone in A. alternata. The increase of fungal VOCs can be affected by tissue degradation and/or fungal metabolism of apples during decay.