Wine chemistry has always been a mystery even to enthusiasts of fermented grape juice. Yet some chemical processes are crucial to understand in order to increase wine appreciation.
While blending requires art and imagination, proper winemaking calls for in-depth chemistry. Wine’s chemical dimension underlies its beauty.
One of the most important “ingredients” of wine is oxygen and the way it affects taste. Oxidation (exposure of wine to excessive amounts of air) and reduction (excluding air to the extent possible) are linked opposites.
Oxidation occurs when electron flow diminishes, and reduction, when it increases. Hydrogen atoms increase reduction and oxygen reverses it.
Oxidized wines were quite common three decades ago. Even today some tradition- bound wineries in Western Europe and many in Eastern Europe make oxidized wines.
Wines stored in half empty upright casks for extended periods oxidize; severe oxidation takes place when barriques are improperly topped. Sloppy winemaking (leaky barrels, use of concrete fermentation vessels for too little volume, unsanitary conditions) causes oxidation, and can be easily prevented by using stainless steel tanks, inert gases to blanket half-empty containers and generally excluding oxygen whenever possible.
German winemakers pride themselves in using reductive technology to produce vibrant, fruity white wines. On the other hand, old Tokaji, sherry and Madeira wine makers prefer to use oxidative technology.
New World winemakers specializing in red wines have embraced reductive technology to produce fruit-forward, instantly appealing red wines. Such wines appeal to young consumers, who like to spend little and enjoy a fruity strait-forward wine
Reductive-technology-red-wines of low acid and pH value are meant to be consumed within a year or two of harvest.
Reductive technology wines can smell “foul” from too much fruit (hydrogen atoms in excessive quantities are responsible for this), but reverse once the bottle is opened and the wine is exposed to oxygen for a few hours.
In some cases eight to 12 hours may be required to “liberate” the wine. This time can be substantially reduced by decanting wine in a well-designed (broad bottomed) decanter. If you consider the surface of wine exposed in the neck of a bottle and that in a suitable decanter, you can visualize the difference. To accelerate the process, decant the wine back and forth for a few times. On the other hand very old red wines should be decanted (to eliminate sediments), and consumed within approximately 30 minutes.
Old wines (40 or more years) tend to oxidize, and literally turn mahogany to black within minutes after decanting. You can easily determine the difference in taste by opening six bottles of the same wine at different time intervals (first 12 hours, second 10 hours etc) and decant into identical decanters.
Taste all “blind” to determine the difference among all. Once you pinpoint the optimal time, use it as a guideline.
Longer oxidation will fail to improve the wine; in fact the process will reverse.
The idea of barrel aging is slow of oxidation – a process in which the density of wood plays a significant role. In hard wood barrels, oxidation would be minimal and in porous wood (grown in warm climes) much faster. Of course, barrels impart flavours, tannins, and textural changes in addition to oxidation.
Even some very famous and expensive white Burgundy, Cotes du Rhone, Jura, Tokaji from Hungary, and sherries benefit from long, controlled oxidation.
Proper red wine making requires controlled oxidation.
Consumers and sommeliers can tale advantage of this principle whenever they consume or serve wine.