Determination of Penicillium roqueforti toxin by reversed-phase high-performance liquid chromatography

Secondary Metabolites from Penicillium roqueforti, A Starter for the Production of Gorgonzola Cheese

The presence of mold in food, although necessary for production, can involve the presence of secondary metabolites, which are sometimes toxic. Penicillium roqueforti is a common saprophytic fungus but it is also the essential fungus used in the production of Roquefort cheese and other varieties of blue cheese containing internal mold. The study was conducted on industrial batches of Penicillium roqueforti starters used in the production of the Gorgonzola cheese, with the aim to verify the production of secondary metabolites. Nine Penicillium roqueforti strains were tested. The presence of roquefortine C, PR toxin and mycophenolic acid was tested first in vitro, then on bread-like substrate and lastly in vivo in nine cheese samples produced with the same starters and ready to market. In vitro, only Penicillium out of nine produced roquefortine C, four starters showed mycophenolic acid production, while no significant amounts of PR toxin were detected. In the samples grown on bread-like substrate, Penicillium did not produce secondary metabolites, likewise with each cheese samples tested. To protect consumers' health and safety, the presence of mycotoxins needs to be verified in food which is widely consumed, above all for products protected by the protected denomination of origin (DOP) label (i.e. a certificate guaranteeing the geographic origin of the product), such as Gorgonzola cheese.

Roquefortine C occurrence in blue cheese

Several strains of Penicillium are used for the production of mold-ripened cheeses, and some of them are able to produce mycotoxins. The aims of the research were the determination of roquefortine C and PR toxin in domestic and imported blue cheeses, the identification of the penicillia used as starter, and the investigation of their capacity for producing toxins in culture media. Roquefortine C was always found in the cheeses at levels ranging from 0.05 to 1.47 mg/kg, whereas the PR toxin was never found. The identification of the fungal strains present in the domestic cheeses included Penicillium glabrum, Penicillium roqueforti, and Penicillium cyclopium in the Gorgonzola "dolce" and Penicillium roqueforti in the Gorgonzola "naturale"; in one case, the presence of Penicillium crustosum was observed. The strains isolated from the foreign cheeses belonged to P. roqueforti. The strains were able to produce between 0.18 and 8.44 mg/liter of roquefortine in yeast extract sucrose medium and between 0.06 and 3.08 mg/liter and less than 0.05 mg/liter when inoculated in milk at 20 degrees C for 14 days and 4 degrees C for 24 days, respectively. Linear relations between production of roquefortine in culture media and cheeses did not emerge. PR toxin ranged from less than 0.05 to 60.30 mg/liter in yeast extract sucrose medium and was produced in milk at 20 degrees C from only one strain. The low levels and the relatively low toxicity of roquefortine make the consumption of blue cheese safe for the consumer.