García-Fontán, M. C.

Malcata, F. X.

Pintado, M. E.

Reis, P.

Tavaria, F.

English

Repositório Institucional da Universidade Católica Portuguesa

216 THE AUSTRALIAN JOURNAL OF DAIRY TECHNOLOGY. VOL. 61, NO. 2 – JULY 2006POSTER PRESENTATIONEffect of alternative technologicalmethodologies on the yeast profile inSerra da Estrela cheeseIntroductionSerra da Estrela cheese is probably the most popular traditionalcheese in Portugal. This semi-soft cheese has been produced forcenturies on farms in the interior, mountainous regions of Serra daEstrela and currently has a Protected Denomination of Origin(PDO) status – granted via Act 42/85 of 1985; these regions coveran area of 3140 km2. Serra da Estrela cheese is manufactured fromraw ewe’s milk of a native breed (Bordaleira da Serra da Estrela)using dried thistle flowers (Cynara cardunculus L.) as a coagulant– without the addition of any starter or secondary microflora(Anonymous 1985; Macedo et al. 1993). Since no starter cultureis added, the native microflora plays an important role throughoutcheese ripening.On the other hand, it is widely accepted that cheese offers aunique ecological niche that constrains the ocurrence and activityof specific yeasts (Fleet 1990; Viljoen 2001). Due to their inherentcapacity to adapt to complex matrices, yeasts may play either abeneficial or detrimental role in cheese production. Hence, theirprofiles were monitored in Serra da Estrela cheese, manufacturedaccording to alternative technological methodologies.Materials and methodsIn this study, two batches of experimental cheese weremanufactured; one of them was according to the traditionalprotocol (Macedo et al. 1993) and the other used a novel apparatus– a closed cylindrical, double-jacketed cheese vat with a 50 Lcapacity (it will allow semi-automated cheesemaking on a smallscale). Each batch was sampled at six ripening times (1, 7, 14, 21,35 and 60 d) and assayed for microbiological changes via theenumeration of yeasts on Potato Dextrose Agar supplemented with1%(v/v) lactic acid solution (10% w/v) and incubated at 25ºC for5 d. All experiments were performed in duplicate.Results and discussionThe average counts of viable yeasts in cheeses manufacturedaccording to the traditional protocol or the semi-industrial protocolare shown in Figure 1. Yeasts are present from the initial stages,as they are already present in raw milk. In general, yeasts wereoften found in cheeses manufactured according to the traditionalprotocol, possibly due to the poor prevailing sanitary conditions.Viable counts increased at later stage of ripening. In semi-industrialcheeses, yeasts were found at higher levels from the second weekon, possibly owing to environmental contamination in the ripeningrooms and the tools in contact with the cheese during manufacture;viable counts increased in the third week and then remainedessentially stable until the end of ripening.AcknowledgementsThe author, M.C. García-Fontán, acknowledges a fellowship(ref. SFRH/BPD/17996/2004) from the Ministry for Science andTechnology (Portugal) and POCTI.ReferencesFleet, G.H. (1990), Yeasts in dairy products. J. Appl. Bacteriol. 68, 199-211.Macedo, A.C., Malcata, F.X. and Oliveira, J.C. (1993), The technology, chemistry,and microbiology of Serra cheese: a review. J. Dairy Sci. 76, 1725-1739.Viljoen, B.C. (2001), The interaction between yeasts and bacteria in dairyenvironments. Int. J. Food Microbiol. 69, 37-44.The authorsM.C. García-Fontán, F. Tavaria, P. Reis,M.M.E. Pintado and F.X. MalcataEscola Superior de Biotecnologia, PortugalCorrespondence to: M.C. García-Fontán, Escola Superior deBiotecnologia, P-4200-072 Porto, Portugal.Fax: +351 22509 0351; e-mail: cgfontan@mail.esb.ucp.ptFigure 1: Mean values, and corresponding standarddeviations (error bars), of viable counts of yeasts incheeses throughout ripening: ■ (traditional protocol) and❐ (semi-industrial protocol). * (Viable counts < 102).

Effect of alternative technological methodologies on the yeast profile in Serra da Estrela cheese

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Effect of alternative technological methodologies on the yeast profile in Serra da Estrela cheese

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