"Naturally" blue wine from Spain: a problem of chemistry ... and oenology

The Owl reported earlier this month on the introduction of blue coloured wine on the French market. Made in Spain, the producers claimed the wine begins life as a traditional white chardonnay but gets its blue tinge after being passed through a pulp of red grape skin that turns blue thanks to the natural pigment anthocyanin.

The oenophiles of France are not convinced about this "natural" business. The scientiic journal  Sciences et Avenir spoke with several scientists from the National Institute of Agricultural Research (INRA), who have doubts about the possibility of obtaining blue wine by this process without having to add other products.
Véronique Cheynier, director of research at the NRA Research, said: “I don’’t see how anthocyanin derived from red grape pulp can make this wine blue,” Dr Cheynier told Sciences et Avenir. “Even if anthocyanin-derived pigments that are blue in colour in an acidic medium have been successfully isolated in the laboratory, these pigments are only present in tiny quantities in grape skin pulp.”
Dr Cheynier added that the pigments are “red in an acidic medium, at low pH, and only turn blue in a basic medium, at a pH higher than seven.” The pH value of wine generally falls between three and four.


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