The role of propionibacteria in the volatile profile of Pategras cheeses

Pategras is a typical semi-hard cheese of Argentina. Over the years, successive technological changes have been applied to its manufacture, being the addition of propionibacteria (PAB) one of the most relevant. The aims of the present work were to determine some physicochemical parameters and volatile composition of commercial samples and evaluate the effect of PAB on volatile profile during ripening, by comparing cheeses made at pilot scale, with or without added PAB. Commercial samples displayed some differences in terms of rough composition, mainly ripening degree. Acids, especially short-chain fatty acids (C-2 to C-4), were the most representative group of volatile compounds, being propanoic acid the most abundant. Alcohols and ketones were other chemical groups that prevailed in the volatile profiles whereas esters and aldehydes constituted a minority fraction. For cheeses made at pilot scale, the levels of several compounds such as diacetyl, acetoin, primary alcohols, ethyl esters, branched-chain aldehydes, branched-chain alcohols, branched-chain acids, and short-chain fatty acids were significantly influenced by the presence of PAB. Most of the changes observed in the volatile fraction during ripening and the differences found between cheeses made with and without added PAB were in agreement with published data. This work provides detailed information about the volatile composition of Pategras cheeses made with the inclusion of PAB, which contribute to the characterization of the most traditional Argentinean semi-hard cheese.