How does alcohol or wine age?

Why a wine ages

This is the most technical and difficult chapter of this chapter, but it deals with a subject that is the most fascinating to all wine drinkers, so it needs to be written about. Perhaps it is the only chapter you will want to reread years later - and then, albeit late, it will have served its purpose. For all of these reasons, I have to use intimidating jargon and bother you with some biochemistry.

When is the best wine?

When you face the unavoidable question, "When is the best wine?" you need to understand at least some of the subject matter discussed here. First of all, you should understand that all properly produced and bottled wines are subject to certain inevitable and significant changes from the moment the bottle is corked in the bottling plant. To put it in very primitive terms, the wine will gradually lose its fruity aroma and flavor (as we saw earlier when describing the primary and secondary aromas and tastes) while at the same time gaining in complexity. It stands to reason that at some point there will come a point at which the complexity can no longer grow, and another point at which there is nothing more fruitful to lose. Sometime in between, or after the second case occurs, the wine will wear off and maybe tip over.

The age curve

The changes in aging are shown in simplified form in the graphic, with a color-coded zone around the point where the lines cross. This yellow zone also shows that the wine does not reach the peak of its development in one day and that it begins to decline the next day. Depending on how long it took to reach its peak, the wine enters a plateau phase in which it neither improves nor deteriorates. The faster he gets there, the shorter this phase will last, and the faster the case (the reverse is also true).

Most subjective judgment of all

However, the simple clarity of the graphic is clouded by a factor that is difficult to calculate: How important are fruity taste and freshness to you, how much value do you place on complexity? There is no right or wrong here, it is a very personal, subjective decision. What's more, it is a decision that will be different as you become more familiar with wine and as complexity gradually becomes more important than fruit sweetness.

The chemical processes

But now to the somewhat more complicated chemistry. The most important change process is the interaction of a small amount of dissolved oxygen (present in young wine) with tannins, anthocyanins, flavones and the various acids. The technical term for this is reduction, because the withdrawal of oxygen gradually reduces the potential for further changes (if new oxygen comes into the bottle because the cork has gone bad, the changes become both faster and more destructive).

Changes in red wine: polymerisation

The changes in red wine are not only easier to observe, they are also better researched than those in white wine. They fall into two main categories: polymerization and esterification. Polymerization occurs through the action of oxygen on the tannins and anthocyanins (the vegetable pigments are colored forms of tannin) and leads to a slow change in the red wine color from the vivid youthful purple to the dark red of middle years and finally to the pale brick red or tan red of old age. The reason for this is the progressive aggregation of anthocyanins and tannins, which first form a fine deposit and later deposits on the sides of the bottle. At the same time, but invisibly, the taste and structure of the tannins (which also change during polymerization) become softer.


This is the other major change that can be attributed to the action of oxygen, this time on acids and alcohol, which form esters and aldehydes. The experts do not entirely agree to what extent these changes have an influence on the bouquet, although pragmatic experience clearly suggests a profound influence. The different opinions are less about the facts of these changes than about the influence they have on smell and taste and how the interaction of all components changes taste and smell. In fact, esterification does not reduce the acidity of the wine: contrary to popular belief, the acidity (chemically) does not degrade as the wine ages. The acidity appears to soften as the wine peaks, simply because the complexity of the other flavor components increases.

Aging white wine: color

Nobody can claim to have deciphered the chemical process by which the color of a well-prepared white wine (fully matured between 5 and 20 years) changes from the light grass-green of its youth to a glowing buttery or golden yellow, still with a green shimmer. In the best of such wines, the color is truly remarkable, as if illuminated by a distant light. It is believed that this comes from the flavones (or flavonoids), a yellow pigment found in grape pods. The problem with this is that Australian Chardonnay, in whose productions the skins stay in the mash for a long time, has a significant proportion of flavones, while with Rhine Riesling there are only traces in the must and in the finished wine. Other variants arise in the Gew├╝rztraminer or Muscat, which can take on a pink shimmer from their pods; Still different is the brown hue that an oxidized or madeirized white wine can get that is insufficiently protected from sulfur dioxide, which is a sure sign of undesirable deterioration.


Because most Australian white wines (from the bigger firms and the best-stocked small wineries) ferment at low temperatures with specially selected yeasts and are strictly protected from oxidation after fermentation, they tend to have a more pronounced yeast at an earlier stage than European wines - and have a fruity aroma. This can range from tropical fruits to a shade of grapefruit (and is generally considered attractive, though not by all producers) but occasionally results in a slightly sweaty, stuffy aroma that I describe as the armpit aroma. As the wine matures in the bottle, the exotic fruity aroma will diminish and the sweaty tone will fade, both pretty quickly. The actual, true aroma of the grape will come out, and any hint of sulfur dioxide that was present when the bottle was filled will go away. Depending on the type of grape, a toasty, nutty or honey-like bouquet is built up, all in connection with the softening of the secondary fruit aroma and sometimes with a blurring of the varietal character of the grape.


The changes reflect those of the bouquet. After the exotic, extravagant, sparkling freshness of a sometimes unbridled youth, the wine becomes more harmonious and softer as it matures, also increasingly richer, with more honey tone, before it reaches the top and possibly loses its former sweet fruit taste - it "dries out". These changes can be felt directly in the mouth and also in the taste.

Red wine: color

The increasing decrease in color density, combined with the change in color tone, has already been explained. Suffice it to say that in Australia special emphasis is placed on both density and youthful purple color: a ripe wine can be light in color as long as it is clear and lively.


The smell of a six-month-old, not yet bottled Cabernet Sauvignon that is said to live twenty years or more is not for the faint-hearted or the uninitiated. He has the raw, untamed strength of a thoroughbred horse that has not yet broken in. Judging such wines at a wine show is a thankless task. But when the carbon dioxide is dissolved in the first fermentation and escapes during the subsequent malolactic fermentation, it takes with it some of the harsher and bitter volatile flavors. The other changes are closely related to polymerisation and esterification, which make the aroma softer and rounder. These changes continue (albeit more slowly) after the wine is in the bottle. Because there are more aroma and taste-forming substances in red wine than in white wine, the extent of the changes is more dramatic and the potential for complexity is much greater.


The reasons for the changes in taste are the same as for the bouquet. When the tannins and anthocyanins have polymerized, esters and aldehydes have formed, the way is free from the usually rough and hard fruit tone of a young red wine to a soft, delicately sweet fruit taste that gradually takes on a gentle earth tone. The tannins also become softer and the astringent young wine turns into a velvety softness. The intensely juicy strawberry-plum tone of a young Pinot, the impressive peppery spice of a young Shiraz, the mixture of black currant and Spanish pepper in a young Cabernet are correspondingly softer when a cedar-tobacco tone appears in the second and third place. Experiencing these changes and then deciding for yourself where you want to draw your line - therein lies a lot of the fascination of wine.