The ripening of blue and Roquefort cheeses is accomplished by the concerted and controlled actions of enzymes of the mold Penicillium roqueforti. The properties and effects of the enzymes involved in flavor development (i.e., proteases, lipase and beta-ketoacid decarboxylase) are reviewed. The metabolic activities of both spores and mycelia of P. roqueforti in relation to fatty acid metabolism and flavor generation are discussed. The chemical composition of blue cheese flavor and the simulation of this flavor by fermentation and formulation are briefly surveyed. Some nutritional aspects of blue cheese are cited.

SummaryThe development of the unique flavor of blue type cheese depends on the concerted action of numerous enzymes of Penicillium roqueforti involved in protein and lipid metabolism. Protease(s) by degrading casein modify the texture and background flavor of the ripening cheese. Lipase by hydrolyzing milk triglycerides provides flavorful fatty acids and precursors of methyl ketones. The enzyme complex involved in the partial oxidation of free fatty acids and the properties of 8-ketoacyl decarboxylase which generates the major flavor components of blue cheese are discussed. Fermentation of P . roqueforti for the rapid production of methyl ketones is briefly reviewed.

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A BSTR A CT The ultrastructural changes occurring during germination of spores of Penicillium roqueforti were examined using transmission electron microscopy on thin sections and freezeetch replicas. The cell wall of the resting spore was composed o f four distinct layers. The outermost layer ruptured and peeled o f f as the spores became swollen during the initial stages of germination. The germ tube, which emerged from the spore, had a thin cell wall which lacked the outer layers observed in the resting spore. As the germ tube transformed to mycelia it acquired extra outer layers so that the cell wall possessed three layers o f material. Germinating spores were multinucleated. Membranous sacs and vesicles and endoplasmic reticulum were observed both in germinated spores and in mycelia.Freeze fracture techniques revealed that the surface of spores was covered with a layer of interwoven fibrils. This technique also confirmed the presence o f distinct layers in the cell wall.The capacity of snail digestive enzymes to hydrolyze cell wall material was demonstrated.