Cheese flavour is an important quality attribute, and is mainly formed during cheese ripening. Besides compounds that are formed from protein and carbohydrates, milk fat-derived compounds are essential for cheese flavour. Before, but mainly during ripening, free fatty acids, lactones, ketones, esters, alcohols and aldehydes can be formed from milk fat, compounds that all contribute their own special character to the final cheese flavour. The formation mechanisms that lead to these compounds are not completely understood, and therefore cheese flavour formation is not under full control.
In this research, firstly an analytical method was developed to detect these fat-derived compounds simultaneously. With this method available, the ripening of a number of cheeses was followed, which showed that notably free fatty acids, lactones and esters are important compounds in Gouda cheese and similar types. Within the free fatty acids, a clear difference appeared between the long- and short chain acids. The latter are predominantly formed in the initial ripening phase, presumably by the native milk enzyme lipoprotein lipase. The short-chain fatty acids are formed in a more evenly fashion, notably by esterases, enzymes from lactic acid bacteria. These enzymes are also crucial for the formation of esters in cheese. Large differences in the formation of short-chain free fatty acids and especially esters prove to exist when different cheeses are compared. Particularly lactic acid bacteria from the –accidentally present– secondary flora seem to be very potent in the formation of these flavour-active compounds. Unlike the current views, the formation of two other classes of compounds, lactones and ketones, seems to be of non-enzymatic nature. In vitro experiments led to the reaction mechanisms and the kinetic data that could explain the formation of these compounds. Combined with the results from a relatively simple determination on milk fat, this also enabled the prediction of the development of lactones and ketones in ripening cheeses up to about 40 weeks.
These results offer tools to cheese producers to increase the control on the formation of fat-derived compounds during cheese ripening.