Occurrence of Penicillium verrucosum in retail wheat flours from the Spanish market

In Spain, low ochratoxin A (OTA) levels have been detected in wheat and different wheat products but no information has been published about the fungi involved in this OTA contamination. Some species of the genera Penicillium and Aspergillus are known to form OTA but few of them are known to contaminate foods with this mycotoxin. Penicillium verrucosum, an important OTA producer typical of temperate and cold climates, is much more frequently found on cereals in countries where they occasionally have OTA problems as in North European countries compared with South Europe, where levels of OTA generally seem to be lower or is not detected. The aim of this study was to determine, identify and characterize the occurrence of potential OTA-producing Aspergillus spp. and Penicillium spp. from retail wheat flours purchased in the Spanish market and used for human consumption. A total of 105 Aspergillus isolates were analyzed in order to know whether they are able to produce OTA and/or citrinin (CIT). None of these isolates were able to produce these mycotoxins. However, 17 suspected P. verrucosum isolates were recovered and confirmed by RAPD analyses. Eleven isolates were OTA producers and 14 isolates produced CIT. Our results confirm the potential risk of OTA and CIT production in wheat flours if stored improperly and the occurrence of P. verrucosum in South European countries. This was the only species able to produce these mycotoxins.