Wine is the fermented juice of freshly picked grapes – most of the time; because some people make an alcoholic beverage from fruits and flowers (elderberries, plums, rhubarb, dandelions, etc.) that they call “wine.”
Also, sometimes the grapes used in winemaking are not freshly picked. In some wine-producing regions, the vintners won’t press and ferment the grapes when they are newly harvested. The grapes will be dried on trays indoors for a few months in order to concentrate the grape sugars which will be used to make sweet wines.
But, for the purposes of this book, think of wine as the fermented juice of freshly picked grapes.
Fermentation
How much alcohol does wine contain?
Most wines contain at least 8% alcohol. Anything less than this amount of alcohol will mean the product is not really stable and will taste thin in the mouth. The average high-alcohol content in wine is 14%.
There are exceptions at both ends of the scale. The lack of alcoholic strength can be compensated by high acidity as in certain German Rieslings, and by natural grape sugar as in some Italian sparkling or still Muscat wines that can have an alcohol content as low as 5%.
Certain wines from warm growing regions can have an alcoholic strength of 16.5% if the grapes are dried before fermentation.
How is alcohol produced?
When grapes are crushed, their juice is released. When this juice comes into contact with yeast, a fermentation starts: the natural grape sugar is converted into alcohol giving off a by-product of carbon dioxide gas. This gas usually disperses into the air. If any CO2 gets bound into the wine, it will give a slight prickling sensation on the tongue. (This happens quite often with Beaujolais Nouveau, Muscadet and certain northern Italian white wines.)
Why does one wine contain more alcohol than another?
The amount of alcohol in the finished wine depends upon the amount of sugar in the grapes at the time of harvesting. Low grape sugars will mean low alcohol; grapes that are rich in natural sweetness will be high in alcohol. (Unless, of course, the fermentation is stopped before all the sugar has been converted to alcohol. This will leave residual sugar in the wine.)
Grapes grown in warmer climates will generally have more sugar than those grown in cool climates. Sunshine, direct or indirect, builds up grape sugars. (Cool nights build up acidity.) For instance, a wine such as Chateauneuf-du-Pape grown in the southern Rhone Valley will have higher alcohol than a Beaujolais grown in southern Burgundy because of the amount of sunshine the respective regions enjoy during the growing season. The French wine law recognizes this fact of Nature and states that for a red wine grown in Beaujolais to be labeled as such, it must contain a minimum of 9 percent alcohol. Chateauneuf-du-Pape, on the other hand, must have a minimum of 12.5% alcohol.
Can a winemaker artificially boost the alcohol content in a wine?
In poor or mediocre years in many wine regions of the world, winemakers will add granulated cane or beet sugar directly to the crushed grapes before or during fermentation to increase the amount of alcohol. These sugars will usually augment the alcohol content by 1 or 2%.
This practice of adding sugar is called chaptalisation after Napoleon’s Minister of Agriculture, Baron Jean-Antoine Chaptal, who first sanctioned the process in France although it had been practiced for centuries. The Romans used to add honey to their fermenting wines to build up the alcohol.
Cold climate wines by definition will contain less alcohol than those grown in hot climates. German wines grown at the northern limit of grape production are generally low in alcohol. Some German Rieslings grown in Mosel, for example, contain as little as 7% alcohol. Contrast this with southern Italian reds that can register as high as 16% alcohol.
What effects does alcohol have on wine?
Alcohol is a great preservative. As an antiseptic it will kill certain bacteria. It will also allow the wine to age without deteriorating if the bottle is properly cellared.
Alcohol also gives the wine weight and substance: the higher the alcohol content, the heavier the wine will feel in the mouth. Although alcohol has no smell, you can detect high alcohol content by the thickness of the residue left on the side of the glass when you swirl it. The heavier the “tears” that fall back to the surface of the wine, the higher the alcohol.
High-alcohol wines will also give the sensation of heat when you smell them and you can feel hotness in the mouth and throat.