The life of wine is long and complicated. It starts at the vineyard, passes through various stages of development at the winery and finishes in the bottle. All stages are important for the production but some are crucial for the quality of the wine. Professionals who create wine from the grapes to the final product in the bottle are called oenologists and the techniques used to make wine - oenological practices. In the next few lines, I will introduce you to some of the more essential and approved oenological practices.
1. Grape harvest. Choosing the right moment for picking the grapes is crucial for the production of high quality wine. The timing of the harvest varies with the different grape varieties and is determined by strict monitoring of several indicators – sugar, acidity, skin colour and aroma intensity. Sugar, acidity, skin can be monitored almost daily by labora- tory analysis and aromas are controlled by tasting.
Depending on the wine category, grapes can be picked by hand in small crates - for quality wines or by mechanical harvester in large containers - for wines produced in larger batches.
2. Sorting. Sorting is not a mandatory step but it is advisable if a winery would like to make quality wines. It is all about the removal of poor quality bunches or berries, as well as those that have been damaged or contaminated. Depending on the technological layout of the winery this can be done before or after destemming.
3. Destemming and crushing. Destemming is the process of separating the stems from the berries - done by grape destemming machines called crushers. This is an important step as stems contain a lot of green tannins and if they remain in the must wine can turn undesirably harsh.
The crushing is done by the same grape crushers, the grapes are crushed after destemming and the process facilitates their fermentation, though this practice is not mandatory either. Lately, quite often uncrushed grape berries are let to ferment. During crushing preserving the integrity of the seed is important as it can release unwanted phenols into the wine and make it taste bitter.
4. Cold maceration. This process can be applied to all wine categories and it is to be decided by the oenologist. The grape must is cooled down to 7-10 degrees Celsius in order to extract the aromatic and colour components from the berry skins before the start of the fermentation process. The duration of maceration is determined by the grape variety and the wine category; it can be from several hours up to few days. During maceration the quality of the must is monitored by tasting to avoid development of a harsh note.
5. Alcoholic fermentation (AF). This is the process of trans- forming sugar into alcohol, during which heat and carbon dioxide are released. Fermentation is started by adding pure cultured yeast to the must. Alcoholic fermentation is the real culprit for turning the grapes into wine. The quality of the future wine depends on the AF. Temperature and measured density (the dynamics of sugar content decrease) of the fermenting must are key indicators to be monitored during alcoholic fermentation.
For red wines it is essential to ensure a continuous contact between the “cap” (skins and other solids) and the liquid. Daily tasting of the fermenting liquid determine what technological manipulations are needed.
6. Malolactic fermentation (MLF). This is the process of transformation of malic acid into lactic acid carried out by selected lactic acid bacteria. The process is indispensable for red wines; the temperature of the wine is a crucial factor for its success. For red wines malolactic fermentation takes place immedi- ately after alcoholic fermentation. After the completion of the process red wines become milder and better balanced. Wines which haven’t undergone this fermentation remain harsh and are considered unstable.
7. Pressing. The separation of wine from the solids (grapes and grape skins) is called pressing. For red wines it is usually carried out in highly aerated environment.
8. Batonnage. A manipulation applied to all categories of young dry wines at the oenologist’s discretion. Its origin is French. The essence of the process is raising fine lees in the wine by stirring it. Depending on the type of tanks in which young wine is kept to ferment, batonnage can be performed with special sticks in barrels or by inert gas in bigger tanks. By working with fine lees wines acquire more body and flavour.
9. Racking. Racking is the process of transferring the wine from one container to another in order to separate in the best possible way the clear liquid from the bottom layer of sedi- ment. This is the simplest, yet most important stage of wine production. Many defects in the following stages of ageing and storing can occur if racking is skipped or not performed correctly. Racking is the mechanical separation of the wine from the sediment, which is beneficial in many ways. The sediment that forms in young wines contains a large quantity of yeast, bacteria, potassium bitartarate and other elements. These substances need to be removed as soon as possible in order to avoid aromas and flavours of mold, dirt and hydrogen sulphide, which can develop in young wine after a prolonged stay in the absence of air.
10. Blending. Blending can be performed at different stages of the production. In some cases wines are blended young and age in blended form, in others they are blended directly before bottling. We can blend wines from different varieties, wines with differ- ent analytical indicators aiming to achieve certain technological parameters or wines with differing organoleptic indicators in order to obtain a particular category of wine.
Blending is a delicate and difficult process, especially when its goal is to achieve a certain high quality category of wine. Tasting the wines that define certain blend is a must before the actual process.
Natalia Gadjeva, oenologist
