Evolution of the volatile components of ewes raw milk Zamorano cheese. Seasonal variation

The evolution during ripening and the seasonal variation of the volatile fraction of Zamorano cheeses were studied by using purge and trap extraction and GC-MS analysis. Concentrations of acetaldehyde, propanal and branched chain aldehydes, 2-methyl ketones, higher molecular weight alcohols, and most esters increased significantly with ripening time. Branched chain aldehydes were more abundant in spring and winter cheeses. 2-Heptanone showed lower concentrations in autumn cheeses, opposite to 2,3-butanedione and 2,3-pentanedione. Alcohols were in general lower in autumn cheeses, except ethanol and 2-propenol, which were lower in summer cheeses. Methyl-, propyl- and 2-butyl esters were in general less abundant in autumn cheeses. Discriminant analysis classified correctly 90% of the cheeses for the season of manufacture and 100% of the cheeses for the dairy of origin. Principal component analysis showed a positive correlation between odour intensity, aroma intensity, pungent taste and branched chain aldehydes, phenyl acetaldehyde and acetophenone. Odour and aroma qualities were negatively correlated with branched chain alcohols, butyl acetate and 2-butyl acetate.