My usual tipple is a pint of stout or, in warm weather, a pint of beer. But in recent years I have also become fond of a glass of red wine.
Irish people traditionally have not been wine-drinkers, but this is changing as the world gets smaller and we get more affluent. Wine is basically a very natural product. The history of wine-making extends back to the dawn of civilisation and will undoubtedly continue while civilisation exists.
Wine is an alcoholic beverage produced by fermenting the juice of grapes. The best grapes for wine are grown on thin, flinty soil in temperate climates worldwide. Many wines are classified according to their region of origin, e.g. Bordeaux, Burgundy etc. Fermentation is a biological process naturally carriedout by micro-organisms such as yeast. All organisms need energy to survive and this is extracted from food.
Yeast generates energy through the controlled breakdown of nutrient sugar in a sequence of chemical reactions whose end-product is alcohol (ethanol). The technical name for this breakdown process is fermentation.
Wine is made simply by crushing the juice out of ripe grapes and allowing the yeasts that grow naturally on grapeskin to ferment the sugar-rich juice. In addition to these natural yeasts, special strains of cultured yeast are often added.
The grape juice remains in the fermenting vats for periods ranging from days to weeks. Usually fermentation is allowed to continue until all the sugar in the juice is converted to alcohol.
Table wines are basically classified as either red, white or rose (pink). Red wines are made from dark grapes whose skins remain in contact with the fermenting grape juice for days or weeks. During this time, tannin and colour are absorbed from the grape-skin by the juice. The mild astringency of tannin is the main reason for the difference in taste between red and white wine.
White wine is either made from light-coloured grapes or from dark grapes, but in the latter case the juice is not allowed into contact with the skins. True rose wines are made from dark grapes, but the skins are allowed in contact with the juice only until they colour it a light pink. The alcohol concentration of table wine varies from about 9 to 14 per cent by volume. The concentration of alcohol in beer normally ranges from about 3.5 to 5 per cent.
Fortified wines such as sherry are so-called because their alcohol and sugar concentrations are increased and their fermentation foreshortened by the addition of a strong alcohol, usually a grape brandy. The alcohol content of fortified wines is usually 15 to 22 per cent by volume.
The world's first wines may have been made in the Caucasus or Zagros mountains of the Middle East as early as 6000BC. It is not difficult to imagine how wine-making was discovered - it can easily be made by accident. Sweet and colourful wild Eurasian grapes have flourished for 50 million years. They were surely popular with early human hunter-gatherers. A handful of squashed grapes in a rock crevice would naturally ferment within a few days. The caveman, or woman, would have been pleasantly surprised when he/she tested a finger-dab of this squash. After that, simple trial and error would have developed more sophisticated wine-making skills.
Wine-making developed naturally with civilisation. Domesticated animals and plants supported the first settled human communities. Grapes were probably cultivated in upland Middle Eastern regions. With more abundant food, Neolithic people had the time to experiment. Fermentation helped to preserve foods and make them more nutritious, yielding alcohol and other anti-microbial agents.
Alcohol is a mood-altering drug and, as readers well know, in moderate intake induces a pleasant feeling of relaxation and wellbeing. As people settled in permanent communities, and as community life became more complex, wine may have played a very important role in smoothing out tensions between people who had given up a more active (and exciting) hunter-gatherer way of life for the more sedate practices of agriculture. Would civilisation have survived without the assistance of alcohol?
Wine-making gradually spread throughout the ancient world. By 3000BC it was used for religious purposes in Egypt. The ancient Greeks cultivated grapes on a commercial scale and sold wine abroad. Greek wines were thick and viscous and had to be diluted with water for drinking.
And wine has always been an important religious drink. This is not entirely explained by observing that priests have always known how to look after themselves. The gas carbon dioxide is also produced during fermentation. Any reader who has peeked into the fermentation vat in a brewery will remember the frenzied appearance of the liquid as it boils off gas. Such bubbling would have added a magical aura to the fermentation process.
The Romans loved wine. As the empire expanded they planted vineyards everywhere the soil and climate suited cultivation of the grape, e.g. Spain, Gaul, North Africa etc.
Wine-making declined in Europe during the early Middle Ages. It was kept going mainly by monasteries since wine was needed for sacramental purposes. In the 12th century the important wine-growing districts began to recover. Today wine-making is a huge worldwide industry. The traditional wine-making areas of the world have been joined by growing industries in North America, Australia, South Africa, Chile and others. I am particularly partial to Chilean wine and I now propose to celebrate finishing this article in appropriate fashion.
William Reville is a senior lecturer in biochemistry at UCC