n-Methyl ketones and Blue cheese flavour

Like that of certain other food products, the flavour of Blue cheese is often an acquired taste. Some people initially find the pugnent, almost peppery, flavour of varieties such as Roquefort, Stilton (shown above), Gorgonzola, Danish Blue and similar cheeses to be overly strong. However, when one becomes used to the flavour, it is quite delicious. The flavour of Blue cheese is dominated by a class of compounds known as n-methyl ketones (alkan-2-ones).
Spores of the blue mould, Penicillium roqueforti, germinate within mechanical openings in the cheese mass to form the blue veins characteristic of these varieties. P. roqueforti produces two potent extracellular lipases which dominate lipolysis in these cheeses which have the highest levels of free fatty acids of all cheese families. However, liberation of fatty acids from triacylglycerols is only the start of the process of producing Blue cheese flavour. P. roqueforti converts fatty acids to n-methyl ketones by a four-step pathway corrersponding to the early stages of beta-oxidation. Heptan-2-one and nonan-2-one (below) are the predominant n-methyl ketones in Blue cheese and contribute greatly to its pungent flavour.

Futher reading:

Collins, Y.F., P.L.H. McSweeney and M.G. Wilkinson (2003). Lipolysis and free fatty acid catabolism in cheese: A review of current knowledge. International Dairy Journal 13, 841-866.