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Identification of the yeasts and bacteria on the surface of Tilsit cheese

Three batches of Tilsit-cheese were produced in different dairies and deliberately smeared with 2 different commercial cultures of Brevibacterium aurantiacum and in one case with Debaryomyces hansenii following a defined protocol starting with the young cheeses. Five, 14 and 28 days after brining the smear of the cheeses was scraped off and approximately 20, apparently different colonies of each, bacteria and yeasts, were isolated from the smears.

The bacterial flora was analysed using a polyphasic approach including denaturating gel electrophoresis (DGGE)of DNA directly extracted from the smear and characterisation of 185 single isolates by phenotypic methods, rep-PCR, 16S-rDNA sequencing, PAGE of whole cell proteins and Fourier Transform Infrared (FTIR) spectroscopy. Despite the application of single strain smear cultures only from the early phase of batch 3 the smear starter was highly recovered (94% of all isolates) whereas recovery in batch 1 was just 40% and it was not isolated from batch 2. Beside Brevibacterium aurantiacum Corynebacterium variabile dominated the early phase of batch 1 but their number decreased during ripening while Microbacterium spp. increased. Batch 2 was dominated by Staphylococci in the early and middle stage of ripening. This genus was also frequently isolated from the middle phase of batch 1 and 3. Generally the complexity of the bacterial population increased with ripening and coryneform bacteria dominated the late phase flora in all three batches.

The yeast flora was investigated by the identification of 184 isolates by FTIR spectroscopy and phenotypic characterisation and appeared to very homogenous in all batches with Debaryomyces hansenii as the dominating species throughout ripening. During the late ripening stage approximately 20% of the isolates were pellet forming varieties of Geotrichum candidum. Batch 3 was unique by the isolation of Pichia triangularis and Candida tenuis from the early and middle ripening stage.

Concerning the identity of the dominant taxa isolated from tilsit surface our results are in agreement with those from previous publications. However, contrasting the results of Bockelmann et al. different population dynamics were obtained from products of different dairies and Corynebacterium spp. (Bockelmann 50-90%) did not predominate the population of any ripened cheese. The different populations obtained from the different products seem to be determined by various factors, including lactate fermentation, technological parameters, the conditions in the ripening cells and the in-house flora. On the other hand it is well documented that problems in the smear development allow the growth of contaminating pathogens.

This implies that by the maintenance of optimal conditions during cheese-making and ripening a relatively controlled smear development may be achieved thereby minimizing this risk.

Moreover, our pilot scale cheese trials demonstrated that by the application of more complex smear cultures, including Arthrobacter arilaitensis, Corynebacterium spp., Microbacterium gubbeenense and Brachybacterium alimentarium beside Brevibacterium aurantiacum and Debaryomyces hansenii reduced the ripening time of Tilsit and positively influenced texture and flavour of the cheeses.

Relevant publications:

Bonaiti C., Chamba J. F., Cogan T., Desmasures N., Gelsomino R., Goodfellow M., Guéguen M.,
Irlinger F., Larpin S., Scherer S., Sebastiani H., Swings J., Thomas A., Vancanneyt M.: Biodiversity and anti listerial activity of surface microbial consortia from Limburger, Reblochon, Livarot, Tilsit and Gubbeen cheeses
Congrilait, Paris 24.-27. September 2002.

N.Bora, H.Sebastiani, R.Gelsomino, M.Vancanneyt, J.Swings, M.Goodfellow, A.C.Ward:
Polyphasic study of actinomycetes on European bacterial smear ripened cheeses by culture dependent and culture independent methods. International symposium on biology of actinomycetes ISBA, Melbourne December 1-5th 2003

M.Hohenegger, N.Bora, R.Gelsomino, S.Goerges, M.Goodfellow, J.Swings, S.Scherer and H.Sebastiani: Surface Microflora of Tilsit-Cheese
IDF-Symposium on Cheese, Prague March 21.-25., 2004

M.Hohenegger, N.Bora, R.Gelsomino, S.Goerges, M.Goodfellow, J.Swings, S.Scherer and H.Sebastiani: Surface Microflora of Tilsit-Cheese
Antonie van Leeuwenhoek 2004 (submitted for publication).

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