No abstract

-In spite of its high production

Cantal is the third French Protected Denomination of Origin cheese. The Cantal cheesemaking process is similar to Cheddar cheese. Both processes involve a milling and a dry salting step which results in a homogeneous salted curd. In order to determine the key parameters of the manufacturing process acting on the specific characteristics of this cheese variety, an extensive and kinetic study repeated three times was carried out at nine stages from the raw milk to 120 d ripened cheese. The microbial ecosystem was explored by numeration and by direct extraction of DNA and PCR-Temporal Temperature Gradient Electrophoresis. Lysis of the lactic acid bacteria was checked by quantification of the intracellular lactate dehydrogenase activity. Carbon sources changes, solubilisation of minerals, proteolysis, lipolysis, and formation of neutral volatile compounds were also assessed. Cheese microstructure modifications and bacterial localisation were determined by confocal scanning laser microscopy. The controlled manufacturing conditions and the use of a complex mixture of starters led to very similar ripened cheeses. The compositional attributes (in particular total solids, fat, nitrogen forms), the lipolysis (0.7 ± 0.2% fat) and proteolysis final extent (34.4 g•kg-1 free amino acids in juice) were similar as well as major neutral volatiles compounds (2-butanone, ethanol and 2-butanol). Nevertheless, lactose and citrate metabolisms differed between the three trials and some free amino acids (Arg, Pro, Ser, Cit, Homocys) concentrations varied drastically during the ripening time course. CLSM micrographs showed that fat globules were disrupted during pressing and bacteria were preferentially localised at the fat/protein interface. As the lactic starter species were the same in the three trials and predominant during the cheese manufacture, the observed differences could result of one or several of the followings: (i) the raw milk microflora which showed to be different leading to growth or metabolism activity of particular subdominant populations during the process and the ripening; (ii) the more or less early lysis of the lactic starters; (iii) the possible interactions between raw milk microflora and the added starters. This extensive characterization of Cantal cheese provides a strong basis for building a rational concept of the key steps in which either technological actions or complementary microbial inoculation could be done in order to limit day to day variations. raw milk cheese / manufacture / ripening / proteolysis / lipolysis / microbial ecosystem / microstructure 摘要-新鲜牛奶制造的法国原产地名号保护 Cantal 干酪的动力学特性。法国硬干酪 (Cantal) 在法国原产地名号保护 (PDO) 干酪产品中产量居于第三位。法国硬干酪的生产方法类似于 切达干酪，两种干酪的生产过程都有磨碎和干盐腌渍和形成均匀盐渍凝块的过程。为了确

Yeasts are commonly detected in cheese. Two yeast species, Kluyveromyces lactis and Pichia fermentans, were isolated at high populations from raw-milk Cantalet cheese, a French Protected Denomination of Origin hard cheese. To investigate the interest of these 2 species as adjunct cultures to promote flavor development of Cantalet cheese, they were added at 10(5) cfu/mL to microfiltered milk. The global microbiological, biochemical, and flavor changes induced by the presence of the yeasts in cheese were determined. Adjunct yeasts were present at 10(6) cfu/g in curd, declined to 10(4) to 10(5) cfu/g in cheese, and did not influence gross composition, content of free amino acids, or content of free fatty acids. By using 8-way gas chromatography-olfactometry in parallel with gas chromatography-mass spectrometry, 30 odorous compounds of Cantalet cheese were identified. The olfactory profiles of K. lactis cheeses contained significantly greater levels of 8 odorous compounds (ethanol, ethyl hexanoate, 4 aldehydes, and 2 branched-chain acids) compared with the control and P. fermentans cheeses. Sensory analysis of cheeses flavor discriminated K. lactis cheeses on only 2 attributes (acetaldehyde and alcohol odors). This study shows that yeast contribution is species-specific and that K. lactis, at a population of 10(6) viable cells/g, can influence Cantalet cheese flavor.