Grape growing, winemaking and wine maturation

Grapes for red wine are usually crushed prior to fermentation. Crush is most often carried out at the same time as destemming. Some winemakers leave a portion of stems in the must to boost the amount of tannin in the wine. If the grapes and stems are not completely ripe, these tannins can be harsh, but stems in the fermentation tank actually make the fermentation easier. The stems help to aerate the cap during fermentation and provide a good drainage structure for the fermenting must to flow through the mass of grape skins.

Some winemakers choose to leave some whole berries in the must, as well. The sugar from these berries is released gradually when the grapes burst during fermentation, elevating the fruit component of the wine. Some producers in Burgundy leave a portion of whole clusters in the must during fermentation.

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In carbonic maceration, all of the clusters are fermented whole. The clusters are carefully placed in the tank and blanketed with nitrogen, which applies pressure to the grapes. Fermentation begins within the berries thanks to enzymes in the grapes. This enzymatic fermentation is called intracellular fermentation. After several days of intracellular fermentation, the berries burst and the fermenting must comes in contact with the yeasts on the outside of the grapes instigating regular alcoholic fermentation.

This form of fermentation gives the wine deep color and pronounced fruit aromas with very little tannins. For this reason, carbonic maceration is most often used to make easy-drinking, early-consumption reds. Beaujolais is a classic example of a region that frequently vinifies its wines using carbonic maceration. This is also a traditional method important to the history of winemaking in Rioja.

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Red wine grapes often undergo a cool-temperature maceration, or "cold soak," on the skins before fermentation. This cold soak helps extract more anthocyanins, the coloring agent in grapes which intensify the color of the wine. Sometimes a cold soak will occur naturally in a cool cellar and the must will need to be warmed slightly to commence fermentation.

If employed, once the pre-fermentation maceration is finished, fermentation is begun, either using indigenous or cultured yeasts. In red wine making, the fermentation is normally carried out at 26–30°C (79-86°F), although, as in white wine making, there is considerable variation depending on the goals of the winemaker.

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When making red wine, it is necessary to extract color and tannin from the skins of black grapes during red wine fermentation. Both the coloring compounds and the tannins are found in the skins of grapes. The juice from most grape varieties is colorless when pressed from the grapes. Coloring compounds and tannins are types of phenolic compounds, or polyphenols.

Extracting tannins is more complicated than extracting color because it's important to only extract the right type of tannins. Tannin molecules create astringency in the mouth because they react with proteins in saliva, rendering them insoluble. Tannin molecules link together to form chains. When the chains of tannin molecules are short, the astringency is compounded, giving unripe, green or harsh tannins. These short tannin chains are the result of harvesting grapes too early before the polyphenols have fully matured. Harsh extraction methods will also lead to harsh tannins. Silky tannins, on the other hand, are produced when grapes are harvested at the peak of physiological ripeness.

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Since tannins are more soluble in alcohol than in water and are more easily extracted at higher temperatures, extraction occurs most effectively once fermentation is under way. One method of extraction is to pump the juice from the bottom of the tank and let it drain through the cap of skins, the process called "pumping over" or remontage. This method also keeps the cap moist and helps prevent the development of volatile acidity. This practice is widely used in Spain's Ribera del Duero, where winemakers feel pumping over is more effective than punching down, which tends to be too aggressive and extracts harsh tannins in their Tinto Fino (Tempranillo) grapes.

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Some winemakers believe that pumping over is too harsh for thin-skinned grapes, like Pinot Noir and Nebbiolo. These winemakers prefer to punch down the cap, submerging it in the juice, rather than breaking it up. Still others use a combination of pumping over and punching down.

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Another method of extracting tannins and color is called déléstage or “rack and return.” In this method, the fermenting must is drained from its original tank into another and then slowly fed back into the tank containing the skins, stems and seeds (called pomace or marc). This method is both highly effective and comparatively gentle. Some winemakers feel this method is a faster, gentler and more effective method than pumping over.

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There are other methods of extraction that draw out more polyphenols, but they are rather harsh on the wine. One method is to heat the grapes before they are crushed (thermovinification), which can impart a cooked aroma and flavor to the wine. This method is used for inexpensive wines.

Another method uses rotofermenters, or rotating tanks that keep the marc constantly mixing with the must. This valuable tool can sometimes be overused, producing awkward, over-extracted and out-of-balance wines.

Winemakers in Port use autovinifiers, that rely on the pressure of the CO2 generated by the fermentation to draw wine up a pipe, which is then sprayed over the pomace when the tank reaches a certain fill level.

The vessel used for fermentation is just as important for red wines as it is for white wines. Wooden vessels of different sizes are used quite often. The alternatives are the same as for white wines: temperature controlled stainless or concrete.

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Once fermentation is complete, red wines are often left to macerate on the skins for a period that lasts anywhere from a few days to a month. Excessive maceration can lead to over-extraction. As with fermentation, more polyphenols are extracted at higher temperatures.

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After maceration, the pomace is pressed, and the wines undergo malolactic fermentation. For the most part, press wine is kept separate from the free run juice until blending. During the blending process all, some or none of the press wine will be added to the blend. Press wine is very concentrated in polyphenols, but also somewhat lacking in fruit. If used to excess, press wine can add harshness without elegance. If used judiciously, press wine can result in great wines. The legendary consultant and mentor Emile Peynaud said the use of press wine is critical to the quality of the final blend. At Ridge in California, up to six press wines are meticulously produced and all are used in the final blend.

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