Role of Selected Yeasts in Cheese Ripening: An Evaluation in Foil Wrapped Raclette Cheese

The purpose of this study was to investigate selected yeasts (Galactomyces geotrichum, Pichia jadinii, Yarrowia lipolytica, Debaryomyces hansenii) for lactic acid utilization, lipolysis, proteolysis and flavour development in foil ripened Raclette cheeses. Foil ripening was chosen in order to exclude the influence of the surface flora. An unreplicated 24full factorial experimental design in two blocks of eight vats was used. In the mature cheeses, the lactic acid content was increased, probably as a result of increased lactic acid bacteria due to the release of yeast metabolites. Yeasts seemed to show either esterase or lipase activity. Furthermore, yeasts revealed peptidolytic activity leading to an increase in smaller peptides and free amino acids. Except for Gal. geotrichum, they also enhanced the formation of biogenic amines.Y. lipolytica was capable of improving the overall sensory characteristics of cheese, but all other species influenced the flavour rather negatively. Since hardly any viable yeasts were detectable in the mature cheeses, the action by yeasts could be attributed to enzymes released after cell lysis.