International audienceThe principal pathways for the formation of flavour compounds in cheese (glycolysis, lipolysis and proteolysis) are reviewed. Depending on variety, microflora and ripening conditions, lactate may be metabolized by a number of pathways to various compounds which contribute to cheese flavour or off-flavours. Citrate metabolism by citrate-positive lactococci or Leuconostoc spp. is important in certain varieties (e.g., Dutch cheeses). Lipolysis results directly in the formation of flavour compounds by liberating free fatty acids (FFA). FFA may also be metabolized to alkan-2-ones and fatty acid lactones. Proteolysis of the caseins to a range of small- and intermediate-sized peptides and free amino acids (FAA) probably only contributes to the background flavour of most cheese varieties, but FAA are important precursors for a range of poorly-understood catabolic reactions which produce volatile compounds essential for flavour.Principales voies métaboliques conduisant à la production de composés aromatiques au cours de l'affinage (revue). Cet article passe en revue les principales voies métaboliques (glycolyse, lipolyse, protéolyse) conduisant à la formation de composés d'arômes dans les fromages. Selon les types de fromage considérés, la microflore et les conditions d'affinage, le lactate peut être transformé en de nombreux métabolites contribuant aux arômes du fromage ou produisant des défauts de flaveur. Le métabolisme du citrate réalisé par les espèces de lactocoques citrate-positives ou par Leuconostoc ssp. est d'une grande importance dans certains fromages, notamment de type Gouda. La lipolyse conduit directement à la formation de composés d'arômes résultant de la libération d'acides gras. Les acides gras libres peuvent également être transformés en alcan-2-ones et lactones. La protéolyse des caséines en peptides de différentes tailles (courts et intermédiaires) et en acides aminés libres ne contribue probablement qu'à la production d'arômes communs à la plupart des fromages, mais les acides aminés libres sont d'importants précurseurs d'une grande variété de réactions cataboliques encore mal élucidées, qui produisent des composés volatils essentiels pour la flaveur

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Cheeses manufactured from ovine raw milk using crude aqueous extracts of flowers of Cynara cardunculus as rennet were compared with cheeses manufactured with a commercial animal rennet. Changes in a number of microbiological, chemical, and biochemical characteristics throughout ripening were followed in attempts to get scientific insight especially into the primary proteolysis brought about by this plant rennet in cheese. Using averages and corresponding 95% confidence intervals, it was concluded that the type of rennet had no significant effect on cheese composition (e.g., moisture, fat, protein, salt, and pH at the center and at the surface) over the ripening period but lower microbiological counts of Enterobacteria, Lactococci, and Lactobacilli were obtained for cheese manufactured with plant rennet until 28 days of the ripening. Conversely, several biochemical differences in cheese became apparent as ripening progressed. Electrophoretic analyses of the water insoluble fractions from cheeses manufactured with either rennet showed that β-caseins were less susceptible to proteolysis than αs-caseins and that the animal rennet was more proteolytic on β- and αs-caseins than the plant rennet; cheeses manufactured with the plant rennet exhibited higher levels of WSN/TN than cheeses manufactured with the animal rennet, although the former showed lower levels of TCA/TN and lower levels of PTA/TN. The peptide profiles of water-soluble extracts of the cheeses obtained by reversed-phase HPLC exhibited different patterns at all stages of ripening for the two rennets utilized, thus conveying important qualitative information for fundamental differentiation of proteolysis effected by either rennet. Keywords: Rennet substitute; Cynara cardunculus; ovine cheese; ripening; proteolysis

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NaCl by cardosins in aqueous extracts of Cynara cardunculus flowers was investigated using urea-polyacrylamide gel electrophoresis and reversed-phase high performance liquid chromatography. Caprine caseinate underwent more extensive degradation than ovine caseinate under the same conditions (pH 6.5 and pH 5.5); proteolysis of ␤and ␣ s-caseins in ovine and, to a lesser extent, in caprine caseinates was reduced in the presence of 5% (w/v) NaCl. Peptide profiles of the pH 4.6-soluble extract had different patterns throughout ripening arising from the different specificity of cardosins toward ovine and caprine Na-caseinates. The major cleavage sites in ovine (caprine) caseinate were Phe105-Met106 (Lys116-Thr117) for-casein, Leu127-Thr128 and Leu190-Tyr191 (Glu100-Thr101, Leu127-Thr128, Leu136-Pro137 and Leu190-Tyr191) for ␤-casein, Phe 23-Val 24 (Phe 23-Val 24 , Trp164-Tyr165 and Tyr173-Thr174) for ␣ s1-casein and Phe88-Tyr89 (Ser9-Ser10, Phe88-Tyr89 and Tyr179-Leu180) for ␣ s2-casein.