Spitting it out is in, especially in Paris

Spitting is frowned upon in polite society -- unless the spitter is engaged in tasting wines. "It's by spitting out the wine that you will be even more distinguished in society," says Pierre-Jules Peyrat, a Paris wine specialist.

Visitors taste red wine at the Chateau la Dominique in Saint-Emilion, southwestern France. GEORGES GOBET / AFP

Holding forth before a rapt crowd at a wine-tasting in the French capital, Peyrat begins by sticking his expert nose into a glass of chilled rosé: it is important to get a good whiff before tasting the wine.

Once in the mouth, the wine is swirled around -- or chewed -- for a few seconds. The taster may then make a "duck face" to allow a bit of air in to detect further characteristics, a step called "grumage".

Next, the mouthful of liquid is spewed back out in an unapologetic burst into a spittoon.

For professionals -- winegrowers, oenologists, sommeliers, wine merchants -- tasting wine means assessing its appearance, or robe, its interaction with the surrounding air, its aromas and finally its taste, as well as its "structure" in the mouth.

The first step is to identify the wine's basic quality: is it bitter, sweet, salty, acid or umami -- that elusive taste between acid and sweet that is much prized in Asia?

The appraisal then turns to the tactile sensation the vintage creates: coarse, astringent, effervescent?

Spitting the wine out is intrinsic to a tasting.

"People think swallowing the wine will give you more aromas, but that's false," says Olivier Thienot, who founded the Ecole du Vin de France in 2003.

"The aromas often come after the spitting," agrees Christophe Marchais, an oenologist from western France near the city of Nantes, acknowledging that the act may seem "a bit bizarre" to the uninitiated.

Some object to the sight of good wine seemingly going to waste; others fear looking boorish or foolish, or staining their clothes.

Spitting, when the wine mixes with air coming from the nose, can bring out "other prevalent aromatic notes", Peyrat says, calling the phenomenon "retro-olfaction".

France, the world's leading wine exporter in terms of value, welcomes around 10 million oenotourists each year -- and their sophistication is growing.