Quality and shelf life of white mould cheeses

Penicillium camemberti is the species taxonomically accepted as being responsible for surface ripening of white mould cheeses. The rate of ripening is determined by the rate of germination, mycelia growth, sporulation and enzymatic production by P. camemberti. The appearance of the cheese is determined by the structure and colour of the combined mycelial growth and formation of conidia by P. camemberti. A rapid germination and mycelial growth is also required for P. camemberti to compete effectively against phenotypically closely related contaminating mould i.e. P. commune and P. caseifulvum and other contaminants including strains of Geotrichum candidum and Mucor spp.
The interaction between P. camemberti and the cheese surface as well as external environmental factors e.g. relative humidity and oxygen and carbon dioxide level are important for the uptake of nutrients and the viability of the culture. When cultures degenerates the mould growth on the surface collapses and become brownish. This is a strong limiting factor for the shelf life of white mould cheeses.
Starter cultures of P. camemberti and G. candidum and related contaminants will be screened for rate of germination, mycelial growth, sporulation, appearance and stability on the surface of a cheese model substrate. For selected cultures detailed studies on the effect of environmental factors and cheese compositions will be carried out. The interaction between the primary starter culture and P. camemberti will be included in the studies. In experiments with a model system and cheese the interaction of P. camemberti with the surface and the viability of the culture will be studied in detail by scanning electron microscopy.
Based upon these studies optimal conditions for white mould cheese will be found.