Search

Parallel productions of Austrian Bergkâse from raw or pasteurised milk were perfonned to monitor the effect of heat treatment on physical and sensory properties of the mature cheeses and, in sorne parameters, during ripening. Apart from sorne seasonal variations, analyses of variance showed that neither mechanical properties nor cheese body col our were influenced by the pasteuri- sation of the milk. However, sensory characterisation of smell and aroma as weil as of the basic taste categories of the mature Bergkâse samples showed that pasteurisation leads to reduced intensities of the typical Bergkâse flavour but increases bitterness scores significantly. In line with results from preceding papers, it may be concluded that it is essential to use raw milk for the production of Bergkâse with satisfactory product properties. © Inra/Elsevier, Paris. Bergkâse / raw milk flora / pasteurisation / physical property / sensory property

The effects of the indigenous raw milk flora on the chemical composition of Austrian Bergkâse was evaluated by means of repeated cheesemaking experiments from raw or pasteurised milk. GeneraIly, changes caused by the pasteurisation of raw milk did not significantly affect the gross com- ( position of the resulting cheeses but, as monitored by sampIing during maturation, systematically showed effects on proteolysis, Whereas degradation of ast-casein proved to be delayed in cheeses made from pasteurised milk due to effects caused by heat treatment and partial eIimination of the raw milk flora, an enhanced cIeavage of l3-casein was found in cheeses from pasteurised milk. These differences were also evident in the water-soluble fraction and, partly, in fractions containing smaller breakdown products and were presumably caused by heat-induced changes in the plasmin/plas- minogen complex. Additionally, effects of heat treatment and of indigenous raw milk flora on alka- line phosphatase and Iipolysis were observed. © InralElsevier, Paris. Bergkâse / raw milk flora / pasteurisation / composition / proteolysis

Dans un grand nombre d'experimentations faites a grande echelle, des emmentals ont ete fabriques a partir de lait cru, avec addition de 0, 10 et 20 % d'eau au melange caille/lactoserum apres decoupage du caille. Pendant l'affinage de 16 semaines dans des conditions standards, des echantillons appropries ont ete preleves dans les meules de fromages et soumis a des analyses. Les resultats montrent que les parametres de composition, c'est-a-dire les teneurs en matiere grasse, matiere seche et calcium, etaient en partie influences par l'affinage, mais restaient totalement inaffectes par le pourcentage d'eau ajoutee. Toutefois, la dilution du lactoserum reduisait la quantite de lactose fermentescible des fromages non affines et entrainait des differences dans le pH et la teneur en acide lactique. Du fait de l'acceleration du developpement des bacteries propioniques induite par le pH, la degradation des lactates a ete trouvee plus prononcee dans les emmentals fabriques avec une addition de 20 % d'eau. En consequence, les taux eleves d'acide propionique et l'acceleration de la formation de l'ouverture etaient evidents dans de tels fromages. D'un autre cote, la quantite croissante d'eau additionnee au melange caille/lactoserum entrainait une reduction de la degradation de la caseine α s1 et une baisse des parametres de proteolyse secondaire. De plus, la contrainte et la deformation a la fracture apparente etaient tres affectees par l'addition d'eau. Les emmentals fabriques avec 20 % d'eau montrent un taux significativement plus eleve de contrainte a la fracture, qui peut etre percu comme une mesure instrumentale de la fermete sensorielle. Comme de plus grands taux de deformation a la fracture impliquent generalement une elasticite sensorielle croissante du fromage, la technologie de l'addition d'eau semble etre un outil approprie pour minimiser les defectuosites sensorielles (fromage a « pâte courte » de consistance), ameliorer la capacite de stockage et diminuer le risque d'une fermentation tardive.

Summary - Randomly-selected Austrian bacterial surface-ripened cheeses were examined for changes in the microbiological composition of the smear. The bacterial counts of the Tilsit cheeses from 14 cheese plants and of 3 types of soft cheeses selected varied fram 1()4 ta 109 cfu/cm2 smear 3 d after manufacture and fram 108 ta 109 cfu/cm2 smear after a ripening period of 3 weeks. The flora tolerated a NaCI content of at least 80 g/kg in the plate count agar. A total of 386 isolates of coryneform bacteria were identified. The bacterial flora proved ta be of mixed population. However, Brevibacterium linens accounted for a large share of the flora, comprising 30% of the total bacterial count, Besides Brevibacterium linens, the other main types found ta be present in the heterogeneous flora were creamcoloured and yellow-pigmented coryneforms, which were predominantly identified as Arthrobacter globiformis and Brevibacterium ammoniagenes. The coryneforms isolated fram the cheeses 3 d after manufacture were more prateoly1ic than those isolated at later stages of ripening.