Microbiological, compositional and biochemical characterisation of PDO Canestrato Pugliese cheese

Microbiological, compositional and biochemical characterisation of the Protected Designation of Origin (PDO) Canestrato Pugliese cheese made from raw ewes' milk is reported. Very few differences were found between two batches of cheese analysed during 150 d of ripening. Fully ripened cheese contained a total of log 7.7 cfu g-1 mesophilic bacteria, log 4.6 cfu g-1 presumptive enterococci and log 4.0 cfu g-1 presumptive staphylococci. Coliforms were detectable in fresh but not in fully ripened cheeses. Streptococci decreased, while lactobacilli increased during ripening. Lactobacillus delbrueckii, L. fermentum, L. helveticus, Streptococcus thermophilus, Lactococcus lactis subsp. lactis, L. plantarum, L. casei and L. reuteri were identified during ripening; the thermophilic strains were probably derived from the natural starter used, the others were probably components of the adventitious microflora. Urea-PAGE electrophoresis of the water-insoluble fraction and the Reverse Phase-HPLC of the ethanol-soluble sub-fractions were good indices of cheese-ripening time. As shown by multivariate statistical analysis, samples after 90 to 150 d of ripening were differentiated from the others. Fully ripened cheese contained ca. 10 mg g-1 of total free amino acids. The concentrations of total free amino acids and, especially, of glutamic acid, lysine, leucine and valine increased throughout cheese ripening. Fully ripened cheese contained ca. 1,315 mg kg-1 of free fatty acids; butyric, caproic, palmitic, oleic and linoleic acids were found at the highest concentrations. In contrast to proteinase and lipase activities, peptidase, as well as esterase activities, increased progressively during ripening. The greatest increase in the peptidase activity occurred when the number of lactobacilli in the ripening cheese was at its highest level.