When wine has a thirst for research. © FOTOLIA, Fotolia

When wine has a thirst for research

The broad palette of rosé wines

Controlling the colour of rosé wines is a crucial challenge for wine-makers so that they can guarantee the quality of their products.  A major study screened a collection of 298 wines from throughout the world in order to link their colour and their phenolic composition.  A high-throughput, sensitive and targeted metabolomics analytical method was developed for this purpose.

Updated on 10/14/2013
Published on 10/14/2013

Colour is one of the main criteria (if not the principal criterion) used to define rosé wines.  It is also an essential element when appreciating the quality of these wines.  In terms of both its nuances and its intensity, colour is intimately linked to the grape variety and the method used to produce the wine.  It is dependent on the presence of pigments (anthocyanins) and also of other phenolic compounds: phenolic acids (hydroxycinnamic acids, etc.) and flavanols (tannins, etc.) extracted from the grapes, and numerous derivatives arising from their reactions during wine-making.  Control of this colour requires a clearer understanding of these compounds, their colour properties and their reactivity.

Extraction of these different compounds during wine-making is dependent on their location in the grape, their solubility and on the winemaking process,  especially the duration of maceration.  Thus phenolic acids present in the flesh are the principal phenolic compounds found in white wines obtained by direct pressing.  The maceration used to produce red and rosé wines encourages the extraction of anthocyanins and also tannins from the skins.  In principle, therefore, the proportions of these families in rosé wines (short maceration) differ from those found in red wines (long maceration), which may have an effect on how these compounds react in the wines and the proportions of the different derivatives that develop.

 

Mapping of the pigments in 298 rosé wines from 21 countries

INRA, the Centre du Rosé and the French Vine and Wine Institute (IFV) Joint Research Unit Qualinnov thus initiated characterisation of the phenolic composition of 298 rosé wines in an attempt to link this with their colour.  These wines from 21 different countries were taken from the worldwide rosé wine collection held by the Centre du Rosé and the Union of French Oenologists.

 

A specific and sensitive method to quantify phenolic compounds

The Polyphenols Platform run by the INRA Sciences for Oenology Joint Research Unit (UMR SPO) developed a high-throughput method to analyse the phenolic composition of these wines.  This method, based on coupling ultra-high performance liquid chromatography (UHPLC) with triple quadrupole mass spectrometry (ESI-QqQ-MS) used in MRM (Multiple Reaction Monitoring) mode, enabled quantification of the phenolic compounds present in the wines.

Using this targeted metabolomics approach, analysis times were reduced from 80 minutes to 30 minutes, with a major gain in sensitivity. Thus 125 compounds could be identified, versus 36 found with the standard method used previously (HPLC-UV-DAD).

In parallel, the characteristics of wine colour were acquired using UV-visible spectrophotometry by the UMT Qualinnov.  The data resulting from these two analyses were then combined and processed using chemometrics techniques.

According to the initial results, the broad range of colours observed in the rosé wine collection resulted from a series of pigments arising from the reactions of anthocyanins from the grapes with hydroxycinnamic acids on the one hand and tannins on the other. Thus the styles of these wines could be linked to their polyphenolic profiles, which reflect the characteristics of the grape variety and wine-making mode.

Contact(s)
Scientific contact(s):

The Polyphenols Platform

Open to use by industry (analytical services, availability of equipment and/or contracted research projects), the IbiSA-accredited Polyphenols Platform offers a whole series of methods (mass spectrometry, nuclear magnetic resonance, spectrophotometry, chemometrics) that are specifically dedicated to the study of phenolic compounds.  The platform can provide technical and advisory support in response to three types of demands:

  • structural characterisation of phenolic compounds (plant constituents, products that form during food processing operations)
  • rapid characterisation of the phenolic composition of a large number of samples (polyphenolic profiles)
  • study of the organisation of supramolecular systems involving phenolic compounds in interaction with other compounds (proteins, polysaccharides)

Website: http://www5.montpellier.inra.fr/spo/structures_collectives/Plate-forme-Polyphenols

The rosé wine market

Rosé wines now account for slightly more than 9% of world wine production, or 24.1 million hectolitres, versus 20 million in 2002.  Three-quarters of this total volume is produced in  Western Europe, and a quarter of this in France, far ahead of the USA (15%), North Africa and Eastern Europe (2%, or 500,000 hectolitres).  France is thus the leading producer in the world of rosé wines (27% in 2011), or 6.5 million hectolitres (versus 4.5 million in 2002), followed closely by Italy, Spain and the USA, whose production is close to 4 million hectolitres.  With an annual consumption of 7 million hectolitres, France is thus a net importer of rosé wines.  Germany produces about 770,000 hectolitres and consumes twice as much, in the same way as Northern European countries that produce none.  With 1 million hectolitres, the Provence region alone accounts for nearly 5% of world production of rosé wines.

Source: CIVP/FranceAgrimer Agrex consulting