Production of alcohol
Alcohol is produced after fermentation of sugar (in grape, malt, etc) by yeasts. This process will carry on spontaneously until the alcohol concentration is 15%. At this point the alcohol will inhibit the yeast and no further fermentation will take place. The substances produced by this process are inter alia natural wine, beer and cider.
Distillation is a process whereby the alcohol level can be increased to absoluteor 95 to 100% alcohol. This process produces distilled beverages such as brandy, whisky, et cetera. Fortified drinks are produced by fortifying natural wine with distilled spirits (eg sherry and port).
The alcohol concentration of natural wine is therefore less than 15%, distilled spirits more than 40 to 42% and fortified beverages in the mid 20%. This is the reason why an opened bottle of distilled or fortified drink will retain its taste, as the alcohol at that percentage inhibits the growth of all yeasts, including those producing vinegar. The same does not apply to an opened bottle of white or red wine, as the alcohol is easily transformed into vinegar.