A fruity flavour note is traditionally regarded as a defect in cheese varieties such as Cheddar (Bills et al. 1965; McGugan et al. 1975; Horwood et al. 1987). However, fruitiness is an attribute of other cheese varieties such as Parmesan and Parmigiano Reggiano (Dumont et al. 1974; Meinhart & Schreier, 1986). It is well accepted that esters such as ethyl butanoate and ethyl hexanoate cause the fruity flavour described as apple-like or pineapple-like in raw milk and cheeses (Bills et al. 1965; Engels et al. 1997; Friedrich & Acree, 1998). The development of fruity flavour is often attributed to the esterification of free fatty acids and ethanol by esterases from lactic acid bacteria and psychrotrophic pseudomonads (Hosono et al. 1974; Morgan, 1976).