Enzyme-derived flavours from lipids

An important but imdefined role of milk fat in the development of natural cheese flavour characteristics is well known (Law et al., 1973). Free fatty acids and presumably lipolysis of fats, play a major role in the development of desirable flavours in mould ripened cheese (Nelson, 1972). Blue cheese t)rpe flavours could be developed from mixtures of skimmed milk and homogenized cream, the homogenization favouring liberation of free fatty adds by milk lipases (Hammer and Lane, 1937). 

Enzymes derived from the stomach of suckling calves and lambs have been found to be largely responsible for the development of characteristic flavours of Italian cheese. The properties of these enzymes (Richardson and Nelson, 1967) and the chemic nature of their activities have been studied. The development of the goaty flavour of Italian cheese, for example, is attributed to the production of low molecular weight fatty acids in milk fat, presumably induced by fat lipolysis. The production of cheese flavour components such as diacetyls and acetoin is facilitated by esterases (Magee et al., 1981). Present day cheese manufacturing practices involve the addition of external esterases to augment the production of the desired flavours. Enzyme modified cheese products are employed to fortify or intensity cheddar cheese flavour in some formulations. 

The direct lipase catalysed esterification process for fiavours has been described by Iwai and Tsujusaka (1984) and by Lazar etal. (1986) for producing geranyl butyrate and black current (2-methyl-pentanylolprenylester) flavours, respectively. The process by Lazar et al. (1986) circumvents the inherent problem of flavour impairment (Schmid, 1987) associated with chemical synthesis of the flavour. 

Lipase mediated production processes for producing flavours and fragrance esters from distillation by-products such as fusel oils have been developed (Welsh and Williams, 1989). Using lipase from Candida cylin-dracea, the fusel oils were converted to their acetic acid and butyric acid esters. Yields of 65.8% and 46.4% for mixed butyric acid esters and acetic acid esters, respectively, were obtained. 

---