Winemaking is the process through which grapes are transformed into wine. Also known as vinification, the production of wine can be broken down into stages starting from the fruit in the vineyard, to the labelled bottle on a wine store shelf.
Winemaking has thousands of years of history and every winemaker has their own set of preferences and techniques to make sure the final result is the highest expression of the cultivated grapes.
The first stage of winemaking is harvesting: when grapes are picked from the vines and transferred to the winery.
Nowadays mechanical harvesting has become quite a popular option, especially due to more cost-efficient technology. However, the finest winemakers still prefer their grapes to be handpicked: not only this causes less stress to the grapes, but it also allows the human eye to perform some checks. Some producers eliminate rotten or not fully ripen grapes on site, before moving them to the famous “sorting table”. As for the size of harvest containers, the smaller the size, the lower the chance for grapes to get crushed.
The time for harvest generally happens at the end of September, however, due to global warming, harvests have occurred earlier and earlier over the past 40 years. In France, harvests are now happening around the second week of September.
Crushing & Pressing
Straight after being sorted but before they are left to ferment, grapes are crushed. Skins and pulp are burst into a free-flow juice called wine must. Some might choose to include (in some cases only partially) or not to include stems in fermentation, with the former known as full-cluster: normally this technique results in more delicate white wines or in red wines with softer tannins.
Back in the day, the grapes were folklorically stomped on with bare feet. Today instead, grape crushers will do the job and are intended to comply with efficiency and hygiene standards.
After crushing, the grapes are moved into the wine press: the first juice flowing is called “free-run”, but further pressing is still necessary in order to get more juice. It’s not uncommon that free-run juice and pressed juice are kept separate and either blended or sold separately later. For example, in Champagne, the terms “cuvee” refers to the first 2,050 litres of grape juice obtained from 4,000 kilos of grapes.
The passage in between crushing and pressing is worth mentioning: for white wines, grapes are pressed immediately after crushing to avoid skin contact and to extract the desired colour, while for red wines, the grapes are pressed only after fermentation.
A ripe grape is full of natural sugars in the pulp and wild yeasts live on the skins. When the skin of the grape is broken after crushing, the fermentation process can begin: yeasts turn sugar into alcohol and the process continues until all the sugar is converted – in the case of dry wines – or when the alcohol level reaches around 15%.
The amount of sugar in a grape depends on the ripening stage: the more sugar, the higher the alcohol level. “Chaptalization” is a technique by which sugar is added during fermentation to increase the level of alcohol , however a natural wine is fermented only with its own sugar.
It takes between 5 and 14 days for primary fermentation. If the must is not separated from skins, colour and tannins will accumulate. Secondary fermentation can potentially take another 5 to 10 days. Also called “malolactic fermentation”, it can either happen later or overlap with the primary stage: harsher tasting malic acid is converted into softer lactic acid, reducing acidity while increasing complexity.
Fermentation is commonly carried out in stainless steel tanks but may well occur in wooden open vats, in wine barrels or, in the case of Champagne, inside the bottle.
Wine can be described as “clear” when there are no particles floating in it. After fermentation, there are two different methods to remove unnecessary or unpleasant residual.
Fining implies the addition of a fining agent to the wine that gathers all particles in a conglomerate of sediment that can be easily removed. The most common organic fining agent is egg white, although this often represents a concern for vegans. Other fining agents can be bentonite clay or activated carbon from charcoal.
Filtration is a more straightforward finishing technique. However, it has proved to be less effective at removing smaller sediment, as several stages are often required to achieve satisfactory results.
Several premium producers either avoid or reduce fining and filtration to a minimum, as that might alter the wine or compromise aromas, flavours, colours, texture or ageing potential.
Ageing & Bottling
Ageing is a way to improve or enhance certain characteristics of a specific wine.
Not every wine is suitable for ageing and each grape has different ageing potential. The duration of the ageing time period depends on the winemaker and the grape variety, but it usually varies between 1 and 5 years and it takes place in oak barrels.
The age of the oak is a key component when it comes to flavour: new oak imparts character and rounded flavours to the wine, while old oak encourages oxidation, ultimately resulting in a smoother and softer taste. Producers usually opt for both old and new oak to keep a balance in their wines – with one being preferred over another according to personal style – and then blend the wines before bottling.
Wine in the cellars is usually kept at a temperature not higher than 10 degrees to slow down the ageing process. As a result of ageing, the colour shifts to deep gold in white wine, while reds turn to brown and brick shades.
Some further ageing can be done directly in the bottles before they’re released for sale.