Volatile Fraction of Ewe's Milk Semi-Hard Cheese Manufactured with and without the Addition of a Cysteine Proteinase

Abstract

A dynamic headspace technique (purge and trap) coupled to gas chromatography-mass spectrometry was used for the study of the volatile fraction of pasteurized ewe's milk cheese. The effect of the addition of the cysteine proteinase of Micrococcus sp. INIA 528 to milk on the formation of volatile aroma compounds in cheese was also evaluated. Forty-five compounds, in total, were identified, including hydrocarbons, alcohols, ketones, aldehydes, esters, terpenes and sulfur compounds. The abundance of most volatile compounds increased significantly (P < 0.05) with ripening time, except those of ethanol and 2,3-butanedione which decreased. Acetaldehyde and some minor components did not vary remarkably during ripening. Acetaldehyde, 2-methyl-I-butanal, 3-methyl-I-butanal, 2-propanol, 2-pentanone and 3-methyl-3-buten-1-ol were the only compounds affected by the addition of cysteine proteinase. The more extensive proteolysis in cheese with cysteine proteinase might have enhanced the formation of volatile compounds derived from amino acids, such as acetaldehyde, 2-methyl-1-butanal and 3-methyl-I-butanal, formed from threonine, isoleucine and leucine breakdown, respectively.