Modified atmospheric conditions controlling fungal growth on cheese

Effective control of fungal growth on cheese under storage conditions is of great concern for the dairy industry. Therefore we designed a research project together with the Danish dairy industry on modelling fungal growth on cheese as affected by the combined effect of storage conditions (O2 and CO2 level, relative humidity and temperature) and the composition of the cheese. All fungal species commonly found on cheese, starter cultures as well as contaminants, were examined.The most important factors influencing fungal growth are temperature, water activity of the medium and the carbon dioxide concentration in the incubation atmosphere. Change in oxygen level from 3 to 25% and pH from 4 to 8 has no significant effect on growth of the fungi. The fungi can be separated into different physiological groups depending on the sensitivity to the tested factors. Fungi associated to the same ecosystem or ecological niche response similarly to the tested factors.Fungi capable of growing under microaerophilic conditions (Penicillium roqueforti and Geotrichum candidum) are both almost unaffected by elevated carbon dioxide level, but strongly affected by reduced water activity. Thus they has a competitive advantage over other fungi in moist conditions with high carbon dioxide levels, such as inside a roquefort cheese or in gas tight grain storage. The key to success in food packaging is to recognise the food ecosystem, as it enables us to identify which micro