Ageing in the Barrel

Once the wine is in the barrel the process of barrel aging begins. Several factors will act on the wine while it is in the barrel, some of them natural, some of them introduced by the winemaker.

How long the wines age in the barrel is up to the winemaker, but for fine red wine it is usually 12 to 24 months. When the wine enters this phase it is young and rough. Hopefully, when it emerges from this phase it will have gained stability, grace, and maturity. How well all this happens is dependent on the following factors:

The Effect of the Oak

Many different types of vessels have been used over the centuries for storing wine, but oak barrels are almost universally used for the storage of fine red wines. There are several factors which make oak barrels uniquely suited for this task.

Oak Flavoring

Perhaps the most obvious quality imparted to the wine from the barrel is the taste of the oak itself. Along with this 'oaky' taste comes additional tannins (giving the wine more 'backbone'), added sugars from the toasting process (giving the wine more sweetness), and enhanced complexity (making the wine more 'interesting'). The effect of this flavoring is directly related to the age of the barrel, type of oak, and toasting treatments during its manufacture. In general, a barrel that is new will impart a lot of oak flavors, but the flavor level will diminish over the years that it is in contact with wine such that barrels that are more than 3 years old will be considered 'neutral', that is, imparting no added flavoring to the wine.

With all this to be gained it should be obvious that winemakers are often tempted to over-use this resource, allowing a condiment to become the main course. I personally feel that many wines today are just too oaky. I prefer the flavor of the oak to be a restrained compliment to the taste of the fruit.

Oxygenation

Oak is a wood with a very large, porous grain. The holes in the grain are small enough that water cannot pass through, but large enough that oxygen can. This allows a small amount of oxygen to be passing into the wine throughout the aging process. This slow aeration has the effect of softening the wine. Two samples of wine tasted side by side would be noticeably different if one were stored in oak and the other in glass, steel, or some other impermeable substance. (It should be noted that, unlike the flavoring of oak, the oxygenation provided by oak barrels will not diminish over time.)

At the end of the day the quality of wines that have been stored in oak are better. This alone is reason enough to use them to store wine until it is ready to bottle.

Racking the Wine

Racking is the process of pumping the wine out of the barrel or tank. This action achieves two purposes; first, the wine is aerated. The addition of oxygen feeds the natural aerobic bacterial processes that are occurring in the wine and second, the various components that precipitate out of suspension in the wine may be cleaned from the bottom of the container. If done carefully the wine that is produced may be crystal clear without any fining or filtering being used.

The first racking is one of the most important, since the volume of precipitate is going to be very high. When the wine is first pumped into the aging vessel it is a cloudy purple color that gradually clears. The materials that sink to the bottom (dead yeast, bits of skin, seeds and pulp) can be permanently removed from the wine in this way.

As the wine ages there are regular cycles of chemical activity that can be tasted. After racking the wine receives a big dose of oxygen. This brings out the fruitiness in the wine and it can taste very good. As the weeks go on the fruit goes to the background and the acids and tannins become more predominate. Gradually the oxygen in the wine is used up and the flavors 'dry up', leaving the wine either tasteless or slightly funky in flavor. At this point racking is done once more and the process starts all over again.

Malolactic Fermentation

Once the wine completes the process of fermentation the wine is not yet considered to be 'finished' wine. Already present in the wine is bacteria that, left to its own devices will convert the malic acid in the newly fermented wine into lactic acid and carbon dioxide. Malic acid has a very hard, sharp flavor, while lactic acid (the same acid found in milk) has a smoother, softer flavor.

This process is not a true fermentation, but was given that name back before the chemical processes that caused it were adequately understood. Ancient winemakers were generally farmers and a rather superstitious lot. They would watch their vats of wine and notice that as the weather warmed up the Spring after harvest the wine would begin to bubble around the same time that the sap would begin to rise in the grape vines as they emerged from their dormant Winter state. It was assumed that there was still some spiritual connection between the vine and it's wine, but we now know that the reason the process started when it did was due to the warmer temperatures that accompany the onset of Spring; the malolactic bacteria is paralyzed by cooler temperatures.

The process of malolactic fermentation (ML) is almost universally used in red wine production to soften the acids and make the wine more stable. Should ML occur once the wine is in the bottle the results would be disastrous; the carbon dioxide would swell the wine and push the cork out of the bottle. The only way to prevent ML from happening is to either sterile filter the wines.

Sulfuring the Wine

The introduction of Sulfur Dioxide to the winemaking process is the single event that led to the modern winemaking industry, since without it wine could not be stored for very long or transported very far. Sulfur dissolved in wine performs two essential functions, as an anti-septic and an anti-oxidant.

Sulfur and Oxygen

There are numerous bacteria found in finished wine that are just waiting for the opportunity to spoil the party, the only thing they lack is oxygen. If the seal on the bottle remains sound and the bottle is not exposed to any extremes of temperature there will be no oxygen for these bad bacteria to work with. The trouble is that we don't live in a perfect world, so sulfur is the second line of defense in keeping free oxygen from being used for bad purposes by evil bacteria. The way it does this is by binding with any free oxygen it finds, thereby removing the oxygen from circulation. If the sulfur binds with the oxygen it will not be available for the malicious bacteria to use for bad purposes.

Sulfur and Infection

The second use of the sulfur is that many negative bacteria are not resistant to it, meaning, they cannot operate in the presence of sulfur. A low level of sulfur in the wine will inhibit most of the processes (both aerobic or anaerobic) that might spoil the wine. In fact, before the use of sulfur wine could not be reliably stored beyond the year in which it was made due to the effects of all these bacteria run amok in the bottles.

Sulfur Allergies

There are some people in this world who are allergic to sulfur, but they are very, very few in number. There are a number of people who assume they are allergic to sulfur because when they drink wines (particularly red wines) they have allergic reactions to it and assume that since the only chemical added to the natural wine is sulfur that they must be allergic to sulfur. As mentioned before, there are more than 500 know constituents to red wine. There is a greater chance of being allergic to one of those 500 compounds than there is of being allergic to sulfur (which happens to be one of the naturally occurring elements in the winemaking process, though in much smaller quantities).