Twenty three strains of Penicillium expansum, as a predominant species, were isolated from 23 (92%) out of 25 grape samples of 17 different grape varieties. The results of the identification of P. expansum strains were confirmed by a PCR method. Most of the isolates of P. expansum (21/23, 91%), when tested for toxigenicity, were bi-toxigenic: they produced citrinin (CIT) and particularly high amounts of patulin (PAT). A validated UPLC-MS/MS method for the determination of PAT and CIT was applied. The limits of quantification (LOQ) for PAT and CIT in grape must and toxigenicity testing samples were 100 and 2 ng/g, respectively. The results of PAT and CIT quantification in 23 grape must samples demonstrated the occurrence of PAT in 10 (43%) grape must samples (mean: 171 ng/g; median: 50 ng/g; and range: 143-644 ng/g) and the occurrence of CIT in two (9%) grape must samples (mean: 1 ng/g; median: 1 ng/g; and range: 2.5-3.5 ng/g). This is the first report on the natural occurrence of CIT in grape must. A validated HPLC-UV-VIS method for the determination of PAT in wine samples was applied, and concentrations in all 23 wine samples were below the LOQ (<10 ng/g).

Center for Health Nutrition and Food National Institute of Public Health Prague Palackeho 3a CZ 61242 Brno Czech Republic

Central Institute for Supervising and Testing in Agriculture Hroznova 65 2 CZ 65606 Brno Czech Republic

Department of Biology Faculty of Science University of Hradec Kralove Rokitanskeho 62 CZ 50003 Hradec Kralove Czech Republic

International Agency for Research on Cancer 150 Cours Albert Thomas 69372 Lyon CEDEX 08 France

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