Development of a synthetic cheese medium for fungi using chemometric methods

Growth, color formation, and mycotoxin production of six cheese-related fungi were studied on nine types of natural cheeses and 24 synthetic cheese media and compared using principal component analysis. The synthetic cheese media contained various amounts of Ca, K, Mg, Na, P, Fe, Cu, Zn, lactate, lactose, and casein. A robust, well-defined, and easily prepared cheese medium was developed for Penicillium commune, the most frequently occurring contaminant on semi-hard cheese. Growth experiments on the medium were repeatable and reproducible. The medium was also suitable for Penicillium camemberti. The medium had the following composition: 100 g of casein, 8.3 g of 90% lactate (90%), 7.9 g of lactose, 7.3 g of CaCl2×2H2O, 2.6 g of MgSO4×7H2O, 26.0 g of NaCl, 20 g of agar, 0.025 g of FeSO4×7H2O, 0,004 g of CuSO4×5H2O, and water to a total weight of 1 kg. The synthetic cheese medium was less suitable for Penicillium roqueforti, Penicillium discolor, Penicillium verrucosum, and Aspergillus versicolor. However, another synthetic cheese medium could be recommended for P. roqueforti and P. discolor. The medium had higher contents of P (5000 ppm, wt/wt), K (5000 ppm), and Zn (50 ppm) and lower contents of Fe (1 ppm) and casein (1%) than did the medium that was suitable for P. commune and P. camemberti.