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Agroscope

Characterisation of Raclette du Valais PDO

Agroscope Science, 115, 2021, 1-47

Agroscope has comprehensively characterised the cheese variety Raclette du Valais PDO (Protected Designation of Origin). With the reference values obtained, cheese-dairy advisory services will be able to identify cheese defects more easily in future.

Raclette du Valais is a smear-ripened full-fat semi-hard cheese produced from unpasteurised milk and mainly consumed melted. This cheese variety has been registered as a Protected Designation of Origin (PDO) cheese since 2007. The bulk of the annual production of around 2300 tonnes is produced in some 20 commercial cheese dairies which cover demand, particularly in the winter half-year when sales volumes are high. During the alpine summering season, Raclette du Valais PDO is also produced on over 100 alpine farms. A certain percentage of production is consumed unmelted as a semi-hard slicing cheese, or dry-ripened into an extra-hard planing cheese over a minimum of nine months.

How is a cheese variety characterised?

As consumers, we probably think first and foremost of the sensory characteristics of this popular cheese, which often inspires memories of bygone holidays in the Valais. For cheese experts, however, characterisation is a question of describing a cheese variety as comprehensively as possible using a wide array of sensory, chemical, physical and microbiological properties.

First-time characterisation of the bacterial microbiome

For the characterisation, a whole cheese wheel was acquired from 21 different cheese dairies producing this cheese year-round. As part of the chemical and biochemical studies, the composition, various fermentation parameters, ripening parameters, biogenic amines, volatile carboxylic acids and the fatty-acid profile were determined. The physical characterisation was conducted by determining curd and melting characteristics. In addition, the flavour profile as well as the sensory properties of the cheese in both a cold and melted state were recorded. Methodological advances achieved in recent years also enabled the  comprehensive characterisation of the bacterial microbiome of Raclette du Valais PDO for the first time, with both the microbiome in the cheese curd as well as the rind microbiome being analysed. Although some of the differences found can be explained by the use of different starter cultures, terroir-specific microbiota find their way into the cheese via the raw milk, thus contributing to the character of this traditional food.

The microbiome in the curd of the 21 cheese wheels examined consisted primarily of 12 bacterial species whose relative frequency in the individual cheeses varied dramatically; only the 12 bacterial species having a relative frequency of ≥ 1% in at least one of the 21 examined wheels are shown.

Valuable Tool for Practice

Numerous variety-specific reference values were developed as part of the characterisation. These are of great benefit to cheese dairy consultants in that they allow the reliable identification of the causes of cheese defects and suggest strategies for improving cheese quality in the event of quality issues (e.g. faulty fermentation owing to undesirable bacteria).

Conclusions

  • The microbiome of a Swiss cheese variety was examined in detail for the first time. A total of 46 different bacterial species were identified in the cheese curd, whilst the rind microbiome with its 203 species was significantly more complex in composition. The most common 12 species accounted for over 98% of the bacterial microbiome of the cheese curd. However, there were significant differences in the composition of the microbiomes between the cheeses of the different producers.
  • The flavour profile of Raclette du Valais PDO was recorded analytically for the first time on the basis of 53 flavour-active compounds assigned to seven flavour families. The flavour profile was decisively shaped by volatile carboxylic acids, which contribute greatly to the ‘cheesy’ taste.
  • During the ripening process, biogenic amines, which can cause health problems, may be formed in cheese. Fortunately, only moderate levels of biogenic amines were found in the 21 wheels of Raclette du Valais PDO examined.

Scientific article

Characterisation of Raclette du Valais PDO

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