Proteolysis and volatile components of reduced-fat cheeses made from ultrafiltered milk and different starters supplemented with lactobacilli and Lac-Prt-lactococci

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 Rsum -Protolyse et composs volatils de fromages teneur rduite en matire grasse prpars avec du lait ultrafiltr et diffrents levains additionns de lactobacilles et de lactocoques Lac-Prt-. La protolyse et les composs volatils ont t suivis pendant l'affinage de fromages teneur reduite en matire grasse, prpars partir d'un mlange de lait (vache, brebis, chvre) ultrafiltr. Pour acclrer l'affinage, un levain (IFPL) contenant plusieurs souches de Lactococcus, Lactobacillus et Leuconostoc (pralablement slectionns pour leur activit protolytique leve), et le * Correspondence and reprints J Rodrfguez et al mme levain additionn d'une souche de Lactoccocus lactis subsp lactis Tl (LacPrc), ont t compars avec un levain commercial (FD). Le type de levain employ n'a pas montr d'effet sur l'hydrolyse de la casine, mais semble entraner des diffrences dans la fraction azote hydrosoluble non volatile. Les profils peptidiques des fromages prpars avec les trois levains taient diffrents et trs caractristiques. La teneur en acides amins des fromages prpars avec le levain IFPL aprs seulement un mois d'affinage tait plus leve que celle des fromages prpars avec le levain FD aprs 3 mois. L'addition de la souche L lactis TI augmentait la production des acides amins pendant l'affinage. Les fromages prpars avec cette souche avaient aussi la plus haute teneur en composs volatils (alcools, ctones, esters et drivs soufrs). fromage matire grasse rduite/ protolyse/ levain/ compos volatil/ lactocoque LacrPrt"