Why Is Red Wine Red?

An odd question you might be thinking, but it’s surprising how many people believe the answer is because the juice from red grapes is red. The truth is the juice from red grapes is the same color as the juice from white grapes, which is how there can be White Zinfandel or why blanc de noir Champagne appears indistinguishable from blanc de blanc. So where does the color come from?

It comes from grape skins, and herein lies a major key to understanding a number of useful things about red wine.

The fermentation process, which turns grape sugar into alcohol, begins with the grapes being smashed. In the old days this was done by getting into a vat and stomping on them. The stompers often got a bit smashed themselves, and great fun was generally had by all. Today the crushing is less romantic but more efficient. Still, the end product remains the same -- a slushy mush called the “must,” in which grape juice, grape flesh, grape skins, grape seeds, and vine stalks are all mixed together.

Yeast is needed to set the fermentation process in motion. Most grapes come with their own yeast attached, so they can in fact begin fermenting without any help. However experience has shown that natural yeasts can yield less than desirable results, therefore special strains have been developed to meet the needs of winemakers. The natural yeasts are killed off using sulfur dioxide gas and a preferred yeast is added. This is not the only thing for which sulfur dioxide is used and its use is a matter of debate and controversy. If you’ve smelled a rotten egg or burnt match, you know what sulfur smells like and can imagine what it can do to a wine if misused.

Once the action gets going the fermentation vat quickly takes on the semblance of a bubbling witch’s cauldron. As the yeast bacteria digest the grape sugar they produce three by-products: alcohol, carbon dioxide gas, and heat. The heat can become so extreme it “cooks” the wine, and this will appear as a defect in the final product. The wine will have a burnt taste. Today heat can be controlled by means of water-cooled stainless steel vats. The combination of heat and alcohol “macerate” the grape must, leeching from it the ingredients that will eventually account not only for a wine’s taste and smell, but its overall quality and survival potential as well. Think of the fermentation vat as stew pot. Just as with a good stew, the longer the contents “simmer” the richer and more complex the result will be.

The release of carbon dioxide gas churns the must, but it also floats the grape skins, seeds, and stalks to the top of the vat where they form a crust called the “cap.” In order to ensure the maximum extraction of ingredients, this cap is periodically broken up and “punched down” into the must. Pumps are also used to draw wine from the bottom of the vat and spray it continuously over the cap. Again the goal is to exact as much as possible from the must by way of taste, smell, and color.

Grape skins are the source of two essential red wine elements, tannin and pigmentation, and the longer their contact with the grape juice the darker and more astringent it will be. If you have ever eaten grape skin by itself, or bitten into a grape seed, or tasted over-steeped tea, then you know what tannin is like. It’s bitter and gives your mouth a dry and puckered feeling. While tannin does not taste good, it plays a vital role in a wine’s evolution. It acts as a preservative, an anti-oxidant that helps keep the wine from spoiling.

Pigmentation is just that, color. And here finally we find the answer to our question What makes red wine red? Or a blush wine blush for that matter. As we noted, the longer the gape juice is in contact with the skins the darker it will be. The French call rose wines vins de nuits (night wines) because their encounter with the grape skins is, so to speak, a one night stand, or quickly encounter. Is it any wonder blush wines blush?

The length of time the skins remain with the juice is first determined by the amount of time it takes for the yeast to do its job. The more sugar present the longer it takes. The other factor is heat. If the must gets too hot or too cold the fermentation process will stop, or become “stuck” as winemakers say. There is a well defined temperature range in which yeast will work. Yeast will also go on strike if the alcohol content gets too high. These limitations can be overcome or controlled through the use of designer yeasts or by employing special fermentation vats that allow water to circulate around their outside through channels and cool things down.

However, once the fermentation process is over, the winemaker may elect to leave the skins with the juice for days or even weeks. Again, as you can imagine, the resulting wine will be that much darker and tannic. In fact such “supersaturated” wines can contain so much tannin they will be virtually undrinkable when young. I’m sure you’ve had such wines, ones that taste harsh and astringent and cause you mouth to feel dry and puckered. Is this a fault?

Not at all, or certainly not necessarily. Most of the truly great red wines do not taste good when young, which is why quality red wines need to be aged, sometimes for years and years, before they reach their full potential. I have said elsewhere that the maturation process is a race between a wine’s tannin and its fruit. Recall the relationship between fruit ripeness, sugar, and alcohol. Really good fruit is ripe fruit and its elevated sugar content means not only that wines made from it will be high in alcohol, but it also means they must remain in contact with the skins and seeds longer, because it takes longer to convert all that sugar to alcohol.

So the “fruitiest” wines can end up with the most tannin as well. When they are young the harshness of the tannin can overpower the more delicate fruit taste, so the wine will not “drink well.” As time passes the influences of the tannin are ameliorated through oxidation and it settles out of the wine in the form of that sludge-like deposit you find at the bottom of older bottles of wine. Then result is a softer, rounder tasting wine.

But just as tannin diminishes over time so too does fruitiness. And this is the race I was talking about. With every passing year the effect of the tannin is lowered a notch or two, but so too is the freshness and strength of the fruit taste. The two, however, do not subside at the same rate and this is what gives we wine lovers hope. Tannins tend to soften faster than fruit dies; so, if there is enough fruit to begin with, and if manages to hang on long enough, there will come a point at which the fruit and tannin will come into balance. It’s at this point of harmonization that a wine is said to be fully mature. It’s at this moment it will taste it’s most glorious, and that can be truly wonderful. This balance can last for years, but eventually the fruit diminishes to a point where the wine turns bad or insipid. The good news is this can take a hundred years or more with some wines.

It should also be evident that if enough fruit is not present from the beginning, or if there is so much tannin it outlasts the fruit, you will end up with a wine that tastes dead, harsh, and alcoholic. In fact, if at any time, or for any reason, the tannin is more assertive than the fruit, you will have a wine that tastes of tannin. In some young wines, or in some matches of food and wine, this can produce pleasant or desirable results. In fact there are those who like the taste of tannin in their red wine and, in moderation, I agree it can add an interesting dimension.

So, why red wine is red? Because of the skins. And the redder it is the more tannin it has absorbed. This information should assist you in your selection of wines or in anticipating how they might taste. If you encounter a wine from a recent vintage that is an inky-dark purple and high in alcohol, the chances are excellent you are faced with a big, powerful young wine that is very liable to taste of tannin. If the wine is light red and limpid, then you are no doubt dealing with one that is less harsh, especially if the alcohol level is respectable (over 12.5%).

A Note on Color and Transparency: These are good indicators of age. Wines become more “limpid” or translucent the older they get, so if you can’t see through the bottle or glass when you hold it up to light, then the wine is probably big and young. When young, red wines are a deep purple. Over time they become crimson, then red, then brick red, then reddish brown. In advanced age, the wine will turn tawny, or orange-brown. So, if you tip your glass and see brown at the wines edges, it’s old.

Color is also a clue to grape variety. This because both the thickness of the skins and the pigment itself differs from variety to variety and this influences hue and depth of color. Gamay, for example, which is responsible for Beaujolais, is cherry red. Pinot Noir is brick-red. Zinfandel a dark but bright purple, while Nebbiolo is almost black.