Potential mycotoxin contamination risks of apple products associated with fungal flora of apple core

During development apples may become infected with mycotoxin-producing fungi without showing surface symptoms at fruit maturity. Cores from five apple cultivars: Ambrosia, Honey Crisp, Golden Delicious, Red Delicious and McIntosh, were aseptically removed from surface sterilized fruit and incubated at 25 °C. The cores were screened for the presence of fungal mycelium and associated mycotoxins. The average percentage of cores with fungal presence was 53.3-58.0%. Twenty five fungal species were identified by sequencing internal transcribed spacers (ITS) of 18S rDNA. The fungi mainly belonged to Alternaria, Penicillium, Aspergillus, Fusarium and Trichoderma species. Fungal pure cultures were inoculated into the apple matrix and incubated for 14 days. Liquid chromatography-mass spectroscopy demonstrated that the isolated fungi had the capacity to produce mycotoxins patulin, alternariol, tentoxin, ochratoxin A and T2-toxin. In addition, mycotoxin-specific genes and/or their transcripts were detected in some of the fungal isolates, but their corresponding mycotoxins were not detected in all isolates containing the genes.