How white wine is made
As we have discovered previously, the colour of wine depends a lot of the process which is used to produce it. This post will delve a little deeper into the process of making a white wine.
Growing and harvesting grapes
As with all wine making the process starts with growing grapes. As we have discovered previously, the grapes used for making white wines can be either white (green) or red (blue / black) grapes. However, there are certain varieties of grape which lend themselves better to producing a white wine, rather than any other style. World wide, it is thought that Chardonnay and Sauvignon Blanc are the most prolific white wine grapes, followed by Riesling, Pinot Gris, Chenin Blanc and others. Probably the most popular red grape varieties used in white wines are Pinot Noir and Meunier. Both are used in the making of Champagne (and other sparkling wines).
In terms of harvest, there are generally two methods of harvesting – by hand, or by machine. Which method is used is determined by a number of factors. Some vineyards use hand harvesting largely because they are too steep or too narrow for machines to be viable. When hand harvesting, grapes are either picked as bunches or individual grapes, but usually as bunches. Machines almost always shake the vine until the individual berries (grapes) fall off. This means they are detached from their stalks.
Prior to pressing the winemaker will remove and MOG (matter other than grapes) which has been collected during the harvest. They may choose to destem any grapes which have been hand harvested depending on the style of wine being made.
It is fair to say that if a winemaker is making a very fresh aromatic style of white wine, it is common to harvest at night when temperatures are cooler to help keep the grapes fresh.
Crushing and Pressing
Once the winemaker is happy that he has grapes free from other materials, crushing can take place. While you may have romantic notions of grapes being crushed by barefoot workers, most crushing now takes place mechanically. As the grapes are crushed, the skins split and some juice is released. This is known as ‘free run juice’. The process of crushing is more delicate than it may sound. This is to avoid crushing the seed which contain oils which can add unpleasant bitterness to the wine.
Once the free run juice has been drained off, the remaining grapes will be pressed. However, it is possible that before this occurs that the winemaker may allow the juice to remain in contact with the skins. Doing this for a short period can add more flavours. Obviously, skin contact with red grapes will result in a rose or red wine, so that is avoided.
Clarification, fermentation and other winemaking processes
The pressed juice and free run juice are combined and clarified to create a clear liquid. The extent to which particles are removed will depend on style of the wine. However, it is generally thought that a clean starting liquid is desirable.
Once a clear juice is available is will fermented. There are a number of choices the winemaker must make about fermentation. Firstly, what type of yeast will be used. All grapes have a certain amount of natural yeast on their skins which can be used for fermentation in a natural style. However, most mass produced wines are fermented using tightly controlled yeast strains for consistency. The strain chosen may also add certain desirable characteristics, aromas or flavours to the finished wine. Secondly, the type of vessel which a wine is fermented in is important.
Generally, aromatic grapes (Sauvignon Blanc, Riesling, gewürztraminer, etc…) are now fermented in stainless steel tanks, which are airtight and temperature controlled. Non-aromatic varieties may be fermented this way, but may also be fermented in oak vessels. Oak has two potential impacts on the wine. It can add desirable flavours from the wood, but it can also allow a small amount of oxidisation which can add depth of flavour to the wine. The influence of the Oak will depend on the size of the vessel.
Once fermentation is completed (either because all the sugar has been converted to alcohol, or because the winemaker has stopped it in order to retain some residual sugar in the final wine) the wine is drained from the tank / barrel. We call this racking off the gross lees, which essentially means allowing the larger dead yeast cells to settle at the bottom of the vessel and taking the wine out leaving them behind. This process does not remove all the dead yeast, but the bigger less desirable cells.
In an earlier post on where wines get their flavours, we explored some of the other wine making processes which are available to wine makers such as aging the fermented wine in oak, leaving it in contact with its dead yeast (lees) to add yeasty flavours, and allow bacteria to convert the harsh malic acid to lactic acid to ‘soften’ the wine. These processes occur following fermentation, but are very much a choice. Again, aromatic varieties are less likely to go through these processes.
Finishing off the wine and bottling
Depending on the style of a wine, a winemaker may at this stage choose to blend the wine with other varieties of wine, or wines made from the same varieties made using different techniques in order to create a particular style. This wine may be matured further in oak if that is inkeeping with the final desired style.
Before the wine is bottled it will go through a final process of clarification and fining to clean it up and to remove any particles still present from the winemaking process. Again, the extent to which is is fined and clarified will depend on the winemaker. Some winemakers believe removing too many particles also removes desirable qualities from the wine. However, we have largely become accustomed to drinking wine which is clear in appearance.
At this stage, the wine will also be stabilised to ensure it does not go off in the bottle. This is where the level of sulphite in the wine will be examined and determined.
The final wine is then bottled and is ready for distribution.
So as you can see there is a lot more to winemaking than just putting the liquid in a tank and then taking it out to put into bottles! The job of a winemaker is, in my view, an incredibly hard one. Throughout the process you have to make a wealth of decisions, all of which could affect the final wine either positively or negatively. Get that wrong and you could struggle to create a saleable wine, get it right you could be winning awards. No pressure!
So next time you reach for a bottle of white wine, I hope you understand a little more about how it went from being a grape growing on on a vine to the final, hopefully enjoyable, end product in your glass. In the meantime, keep exploring this beautiful planet we live on, one glass at a time!