Limited Effectiveness of Penicillium camemberti in Preventing the Invasion of Contaminating Molds in Camembert Cheese

Mold-ripened cheese acquires a distinctive aroma and texture from mold cultures that mature on a fresh cheese wheel. Owing to its high moisture content (a_w = 0.95) and pliability, soft cheese is prone to contamination. Many contaminating mold species are unable to grow at colder temperatures, and the lactic acid produced by the cheese bacteria inhibits further infiltration. Thus, Camembert cheese is generally well protected against contamination by a wide range of species. In this study, cocultures of Penicillium camemberti and widely distributed mycotoxin-producing mold species were incubated on different types of agars, and purchased Camembert samples were deliberately contaminated with mycotoxin-producing mold species capable of growing at both 25 °C and 4 °C. The production of mycotoxins was then monitored by the extraction of the metabolites and their subsequent measurement by means of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) based targeted metabolite profiling approach. The production of cyclopiazonic acid (CPA) was highly dependent on the species cocultivated with Penicillium camemberti, the temperature and the substrate. Contamination of Camembert cheese with Penicillium chrysogenum, Mucor hiemalis, or Penicillium glabrum induced CPA production at 25 °C. Although mold growth on cheese was not always evident on biofilms for certain cultures, except for Penicillium citrinum, which stained the monosaccharide agar yellow, mycotoxins were detected in many agar and cheese samples, as in all monosaccharide agar samples. In conclusion, cheese should be immediately discarded upon the first appearance of mold.