Words by Karen Fick
Red wine is made from dark (red or black) grape varieties and can range in colour from intense violet, typical of young wines, through to brick red for mature wines and brown red for older wines. The colour depends on the grape variety used, the vintage characteristics, the health of the grapes, the wine making methods, the wines PH and the amount of time it has spent in tank, cask and bottle.
Red wines are produced in virtually all the world's wine regions though fewer are produced in cooler regions as a certain amount of heat is required for the grape to develop sufficient pigmentation to produce a proper red wine.
With the exception of the juice from Teinturier varieties of grape, which is red, the juice from dark grapes is actually greenish-white. The red colour of the wine comes from anthocyan pigments which are in the skin of the grape. Much of the process of making red wine is about extracting colour and flavour from the skins.
After harvest, the grapes are gently crushed. The crushing pressure is carefully controlled so as not to extract too many bitter tannins from the pips. In some less tannic grape varieties such as Pinot Noir some stem is retained to add structure to the wine but generally these days stems are removed as they tend to make wine astringent. The mixture of juice, stems, skins and pips is called the must.
After the red grapes are crushed fermentation takes place and it is as this point that red wine production differs from white wine production. Red wines are fermented with the skins, while white wines are fermented without their skins. Red wines are usually fermented at higher temperatures than white wine and until all the sugar is consumed. The higher the temperature the more colour and tannin will be extracted but lower temperatures give a better bouquet, freshness and fruit. Yeast is needed for fermentation and the winemaker can use the natural yeasts that occur on the grape skins and in the cellar or he can add a selected variety of cultured yeast which may or may not have a neutral flavour.
At this stage, if the must does not contain enough sugar to ferment enough alcohol, the winemaker can add beet or cane sugar, this is known as chaptalization. Tartaric, malic or citric acid can also be added now to increase the acidity of the must.
During fermentation the skins float to the top of the must to form a cap or manta. To ensure that maximum colour and tannins are extracted it is important that the juice remains in contact with the skins so the juice is pumped over the cap (remontage) or the cap is punched down into the must (pigeage). Fuller, darker more tannic wines are left in contact with the skins for between 10 to 30 days while lighter wines are separated after just a few days.
White grapes contain co-factors that help in the production of colour so sometimes a few white grapes are fermented with the red. The colour produced when co-factors are present appears to be more stable over time, and mouthfeel, texture, flavours and aromas are improved.
Once fermentation has ended the stems and skins are left to infuse in the wine to extract more colour, tannins and other phenolic compounds.
Techniques for handling tannins are one of the most crucial parts of the modern red wine making process. They begin in the vineyard when growers must ensure that skins and pips are ripe before harvesting. Tannin is extracted faster if there is alcohol present so a wine will have greater tannins if the wine and skins are macerated after fermentation. To obtain lower tannins but lots of colour the maceration process takes place before fermentation begins. This is known as a cold soak.
Carbonic maceration is a maceration process used to obtain light fruity wines which are bright in colour and low in tannin. These wines are intended for drinking young and have a characteristic aroma and flavour of bananas or bubblegum. Whole clusters of uncrushed grapes are put in a closed fermentation vat, smothered with carbon dioxide and left for between one and three weeks. In the absence of oxygen, intracellular fermentation takes place which as well as producing some alcohol produces aromatic compounds, glycerol and reduces sharp tasting malic acid levels. The grapes are then pressed and a normal fermentation process follows. A lesser degree of carbonic maceration will occur even if the closed vat isn't filled with carbon dioxide as grapes at the bottom of the vat are crushed by the weight of those above and some juice is extracted. This juice ferments and gives of Carbon Dioxide thus excluding oxygen at the top of the vat.
The wine is now separated from the skins. The free run wine or vin de goutte runs out of the vat when the tap is opened into wooden barrels or stainless steel, cement or fibreglass vats. The remains (the grape skins, pips and other solids) are put into a press to extract the dark tannic press wine. This will be matured separately and blended in later. Some red wines are now fermented again without their skins.
If the wine is kept at a low temperature and not allowed to oxidise (red wine tends to be oxidised more than white wine) it will not change or develop and will retain its youth and freshness. However, this is not the case if it is put into oak casks. A small exchange of gasses through the pores of the oak supplies oxygen which softens the young wine and reduces the fresh primary aromas. Old oak barrels impart no flavour of their own, but new oak imparts vanillin which has a taste affinity with some grapes, particularly cabernet sauvignon. Small new oak casks (usually 225 litre barriques, also known as barriques Bordelais because they are the size traditionally used in Bordeaux) are sometimes used for maximum flavour. Oak can also help fix the colour and aid polymerization (lengthening of the molecular chains) of the tannins, which softens their taste. If Malolactic fermentation is to take place it is often done in the barrique.
Malolactic fermentation or conversion is almost universal in red wine production. This secondary bacterial fermentation changes the sharp tasting malic acid in the wine to riper tasting lactic acid. The total acidity in the wine is not reduced but the taste becomes less aggressive and the weight in the mouth improves. A winemaker will choose whether to put all, some or none of his wine through this process.
Red wine is aged for between four months (although Beaujolais Nouveau is aged for just days) and four years. During this time the wine is racked (soutirage) several times by running it from one barrel or vat to another to separate the clear wine from the settled sediment or lees. Racking can also provide aeration which can be beneficial to the wines maturation as it can cure wines suffering from reduction and can remove malodorous and volatile sulphides from young wines. The wine may also be fined with a fining agent to remove very small molecules such as proteins so that they do not form a haze in the bottle. The proteins bind to the fining medium which makes them heavy and therefore drop to the bottom of the container.
Some red wines are not fined or filtered and should be decanted before drinking.
Each vat or barrel is tasted separately and the winemaker then puts together his final blend which is then bottled.