TODAY is an important day for the Chevaliers du Tastevin. The chevaliers are an organisation of Burgundy wine growers, shippers and dilettantes of the world of wine; they hold frequent soirees for which they bedeck themselves with black hats and nice red robes, and the piece de resistance of their haute chic is a silver tastevin, a little receptacle for tasting wine which hangs suspended from the neck with orange ribbons. The significance to them, and indeed to the world in general, of November 15th is that it is the day each year on which the Beaujolais Nouveau is released to the eagerly awaiting connoisseurs.
The essence of a good wine is notoriously elusive and ephemeral. Sun soil temperature and water all enter the equation, and even, some believe, the very bedrock over which the vines are cultivated. All these factors, and of course the topography and orientation of the vineyard, combine to varying and undefined degrees to provide what the French call the terroir, the totality of the growing environment of which the wine becomes the ultimate epitome.
Meteorologically, the recipe is simple. Grapes require about 1,300 hours of sunshine every year to thrive, and about 700 millimetres of rain for optimum growth. Ideally, the annual average temperature of a wine producing - region should lie between 14 and 16C, the temperature at certain critical times of the year should never drop below 10C, and extremes of any kind are undesirable.
Tradition has it, moreover, that "struggling vines make the best wine" - that high quality vintages come from poor soils where the plants are almost stunted. The brash producers of the New World, however, have a different explanation. They say that there is no known mechanism for flavour to be communicated from the soil, which therefore does not matter; all grapes really need is lots of sunshine, which leads to high concentrations of sugar, and more of the chemical compounds that contribute to colour, flavour and aroma - and hence to a better wine.
The reason why poor soils produce a good vintage, the modern sceptics say, is that plants continually stressed for lack of water have fewer and smaller leaves, allowing the sunshine unrestricted access to the fruit. The same result with dramatically greater yields, they argue, can be achieved by growing vines in fertile soil, and simply stripping away the foliage to let the sunlight in. But naturally the cognoscenti of the world of wine just sniff dismissively at such sacrilegious liberties with their eternal verite's.