Isolation and identification of flavour volatile compounds in milk and a derived mountain cheese

The study of the volatile fraction of cheese plays an important role in evaluating aroma. Two varieties of Quartirolo, a typical Italian mountain cheese, during 5 processing steps (milk, curd, mould, salting and 45 d of ripening) were examined in order to isolate and identify flavour volatile compounds. Simultaneous distillation extraction was carried out using methylene chloride added with n-nonadecane as internal standard. After 2 h, the procedure was stopped and the extract dried over anhydrous sodium sulphate. Aroma compounds were analysed by gas chromatography and detected by mass spectrometry. About 70 compounds were identified by comparing GC retention times with those of known standards and by mass spectra; they included 12 aldehydes, 13 ketones, 19 free fatty acids (FFA), 11 alcohols, 6 hydrocarbons, 1 sulfur compound and 5 furans. These compounds increased during the cheese making process and reached their maximum at the end of ripening. These changes were evaluated and discussed.