Not all grapes are the same. Big ones, little ones, maybe more juicy if it rains close to harvest, maybe more flavorsome but less plump if they have been left to ripen longer. But as a general rule, about 600 to 800 grapes go into each 750ml bottle.
But that is only one answer. Perhaps we could ask how many different varieties of grapes go into bottles of wine. There the number is much much larger.
Most wine drinkers could name a dozen or more grape varieties. Try it yourself – Cabernet Sauvignon, Chardonnay, Pinot Noir, Riesling, how long a list can you think of? If you visit Cavender Creek winery, your mind may turn to Petit Manseng or Norton. There is even a club (http://www.winecentury.com/ ) for people who claim to have tasted at least 100 grape varieties.
But how many different varieties are there?
To say “nobody knows” doesn’t help. A recent attempt to name and describe grape varieties in a very weighty book gives us a list 1368 varieties which are grown commercially. Experts have made informed guesses of more than 10,000 varieties. To confuse the picture, many of these are called different names in different places (like Syrah and Shiraz, or Pinot Gris and Pinot Grigio).
There is an established science of grape genetics, tracing the ancestry of the grapes that end up in our wine bottles. The stories can be very interesting for wine lovers. For example, Zinfandel, first documented in USA in 1829 is a Californian specialty giving us rich, full bodied red wines (and sweetish pink “blush” wines). In the 1970s, it was identified as Primitivo from Italy. That sparked a small trade war – Italian growers began selling their Primitivo labelled as Zinfandel, much to Californian fury.
DNA testing is a science not limited to episodes of CSI and paternity tests. Plants have their own DNA. Now, with the coming of modern DNA testing, both Zinfandel and Primitivo have been identified as really being Tribidrag. This is a much older grape variety still grown in Croatia, written about as early as 1518.
But where did all these thousands of varieties of grapes come from? They didn’t emerge miraculously out of the mists of pre-history. That’s a story for another day.