How is Red Wine Made?
Red wine! A fascinating drink, how is it actually made?
It all starts in the vineyard. After a season of hard work and with favorable weather, beautifully ripe grape clusters are waiting for harvest in September/October. The harvest can be done either by machine or by hand. The clusters are then brought to the winery. There, it typically starts with evaluating the grapes and removing leaves, rotten grapes, insects, and other unwanted pests. This is done on a Table de Tri, a conveyor belt that vibrates as it moves. On either side of the belt, people carefully separate the healthy grapes from any imperfections. This sorting step is not performed by every winemaker, as it’s understandably an expensive additional step. However, it does improve the quality, and it’s up to the winemaker to decide if it’s worth the effort.
De-stemming the Grapes
The second (or first) step is de-stemming the grapes. The stems of the grape clusters contain a lot of tannins, also known as tannic acid, which tastes very bitter. There are different types of tannins. The tannins in the stems and in the grape seeds are very bitter and harsh. The tannins in the skins, however, are a bit more gentle and give the wine body. This is often experienced as a slightly drying sensation in the mouth, particularly on the teeth and gums. Some grapes have more tannins in the skin than others, which is why some wines have more tannin than others. Sometimes, a winemaker will choose not to de-stem a portion of the clusters, allowing the harsher tannins to add more structure to the wine. The de-stemming process happens in an égrappoir, a de-stemming machine. This device brings the grapes in at the top, where the individual grapes come out at the front, and the stems are deposited at the bottom. Such an égrappoir performs this precise work at high speed with a loud, confident rumble. It’s an impressive machine.
Crushing the Grapes
The freshly de-stemmed grapes are then carefully crushed, but not yet pressed. By crushing the grapes, the skin is gently broken, and the juice begins to mix with the skins. The skins soften during this maceration process, and the natural yeast cells on the grape skins dissolve into the juice. By the way, blue grapes give transparent juice. The color is in the skins, and only by macerating the skins with the juice does the color slowly turn red. If the skins are removed earlier, rosé can be made. From blue grapes, you can also make white wine, known as blanc de noir. Besides the colorants, tannins, and yeast cells, additional compounds such as aroma compounds, bacteria, and fungi are also released from the skins. This mixture of grape juice and solid particles is called must. It’s a rather murky, confused, and sweet substance at this point, which doesn’t yet resemble the beautiful bottled product.
Most winemakers aim to make a deep red wine, as this is often seen as a sign of quality by consumers. However, this perception isn’t always correct, as a light red wine can also have great complexity. This is more dependent on the grape variety used. For example, Pinot Noir has thin skins with much less colorant but can produce fantastic wines with great complexity. There are various techniques to extract as much color from the skins as possible.
For example, macération à froid (cold soaking). The grapes are allowed to soak for a few days in a cool environment after crushing. This softens the skins, so they release more color during alcoholic fermentation. This is done at a low temperature to prevent the fermentation from starting too early. The yeast cells on the skins are already soaking in the juice, but they won’t activate properly below 10°C. They start working only at 15-16°C.
Alcoholic Fermentation of Red Wine
After maceration, alcoholic fermentation can begin. The sugar in the grape juice is converted into alcohol and carbon dioxide by the yeast cells. The fermentation starts at 15-16°C, and during fermentation, alcohol and carbon dioxide are produced along with some heat. This causes the temperature of the must to rise to 32-33°C. If the temperature continues to rise, fermentation will stop. It is therefore important to keep the must at the right temperature with cooling elements. Nowadays, winemakers rarely use only the natural yeast from the grape skins. This method is difficult to control, and fermentation can sometimes stop halfway. At that point, the alcohol percentage is still low, and there’s still a lot of residual sugar in the wine. That’s why winemakers prefer to add artificial, cultivated yeasts, which better guarantee fermentation. These yeasts are also available in different aromas, allowing the winemaker to guide the final flavor profile of the wine.
When alcoholic fermentation is complete, the young wine is separated from the solids by draining. The wine that naturally flows out of the vats, about 85% of the must, is called vin de goutte (drainage wine). The remaining solids (skins, pulp, seeds) are pressed.
Pressing the Must
After alcoholic fermentation, the mass is pressed. By now, we refer to it as wine, not must anymore. The name alone sounds better, doesn’t it? Pressing is done carefully to ensure that the seeds remain intact and do not release their bitter tannins. A modern, so-called horizontal press consists of a large, horizontal cylinder with holes. The grape mass is placed inside, and a large inflatable balloon inside the cylinder gently presses the juice through the holes. The pressure on the balloon is pneumatically controlled. The wine resulting from this pressing is called vin de presse. This wine is strong in flavor and contains a lot of tannins and plant matter.
By the way, pressing is not always necessary in the vinification process; the winemaker may choose to let the juice flow into another vat without pressing. Most of the solids remain in the first vat. This wine is softer and friendlier than the pressed wine.
Aging the Red Wine
The next step is aging the wine. This can be done in wooden barrels, stainless steel vats, or large concrete vats. Young wine is often still a bit harsh, and with aging, it becomes softer and smoother. The decision to age in wood or not depends on several factors. The wine must benefit from wood aging; it should have a certain fullness that complements the oak aging. Additionally, wood aging is simply expensive.
Malolactic Fermentation
Red wine often undergoes malolactic fermentation. This is a second fermentation that occurs naturally, where the sharp malic acid in the wine is converted into the milder lactic acid. This process is typically not done with white wine, as the malic acid in white wine adds extra freshness, which is usually desired. It’s called a second fermentation, but technically, it’s not a fermentation because it’s carried out by bacteria. Just wanted to keep you properly informed.
Filtering the Red Wine
Finally, the wine is filtered. Consumers expect a clear wine. However, filtering also removes some flavor. That’s why some winemakers choose not to filter as rigorously, or at all. The wine is then ready to be bottled and sealed with a cork or screw cap. Generally, the bottles are stored inside the winery for some time before they are distributed.
