Varied volatile compounds are produced by Propionibacterium freudenreichii in Emmental cheese

Directing cheese flavour development requires to know the respective contribution of each of the cheese microflora. Volatile (flavour) compounds produced by Propionibacterium freudenreichii, the main secondary flora of Emmental cheese were identified by gas chromatography-mass spectrometry in mini Emmental cheeses, and in pure cultures of propionibacteria grown in cheese aqueous phase (juice). Selected compounds were quantified. Propionibacteria significantly influenced the amount of 57 out of the 69 volatiles identified in juice. Short-chain carboxylic acids (acetic, propionic, butanoic, hexanoic, and isovaleric acids), esters (mainly esters of acetic and propionic acids), and some ketones and alcohols were more abundant in the presence of propionibacteria, whereas most aldehydes were less abundant. Most of these volatiles were branched-chain compounds. In cheese, the fingerprint of propionibacteria on the volatile profile, despite being less pronounced, showed similar trends as in juice. Carboxylic acids and esters are the most probable cheese flavour-active compounds produced by propionibacteria.