Summary - Proteolysis and volatile components of serni-hard cheeses manufactured from a mixture of cow's, ewe's and goat's milk, with reduced fat content and concentrated by ultrafiltration, were folJowed during ripening. A starter culture (IFPL), consisting of several strains of Lactococcus, Lactobacillus and Leuconostoc, selected previously for its high proteolytic activity, and the same starter with the addition of a concentrate of Lactococcus lactis subsp lactis TI, lacking the ability to utilize lactose and casein (Lac Prr), were tested with the aim of accelerating cheese ripening as compared with a commercial starter (FD). Casein hydrolysis was not affected by the type of starter culture employed, whereas appreciable differences were found in the non-volatile water-soluble nitrogen fraction. The peptide pattern allowed a clear distinction among cheeses made with different bacterial cultures. IFPL cheeses exhibited, after 1 month of ripening, a higher content of total free amino acids than FD cheeses after 3 months of ripening. Furthermore, the addition of L lactis TI to the IFPL culture noticeably increased the release of total free ami no acids during ripening, as well as the content of total volatile compounds. reduced-fat cheese / proteolysis / starter / volatile component / LacrPrt lactococci Resume - Proteolyse et composes volatils de fromages a teneur reduite en matiere grasse prepares avec du lait ultrafiltre et differents levains additionnes de lactobacilles et de lactocoques Lac-Prt-. La proteolyse et les composes volatils ont ete suivis pendant l'affinage de fromages a teneur reduite en matiere grasse, prepares a partir d'un melange de lait (vache, brebis, chevre) ultrafiltre. Pour accelerer l'affinage, un levain (IFPL) contenant plusieurs souches de Lactococcus, Lactobacillus et Leuconostoc (prealablement selectionnes pour leur activite proteolytique elevee), et le