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  Corkscrew Issue 50, March 2007   
Making Wine: After the FermentationMaking Wine: After the Fermentation  Contents 
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Making Wine: After the Fermentation

At the end of alcoholic fermentation, it is now time to do the first racking and to let the wine towards the indispensable journey of aging

 Alcoholic fermentation - or primary fermentation - is an essential process allowing the transformation of the must into wine. At the end of the fermentation, despite what it is obtained can already be defined as “wine”, our beverage still needs to undergo other procedures in order to be fully appreciated. At the end of the fermentation is necessary to do some controls on the stability of wine and on the absence of any possible fault, in order to prepare it in the best possible conditions for the next phase: aging. In the production of wine, every operation plays a fundamental and important role, and most of faults which can be found in wines widely depend on the phases following alcoholic fermentation, in particular in home wine making. Alterations and faults which can develop during the aging of wine are in fact many, it will be therefore needed to adopt specific preventions in order not to damage the job done do far.

 

During the Fermentation of Red Wines


The cask is the most common tool for the aging
of red wines
The cask is the most common tool for the aging of red wines

 The fermentation of red wines requires a higher care than white wines. Skins are allowed to macerate with the wine and, because of the effects of the carbon dioxide developing during the fermentation, they will tend to move upwards by literally floating on the surface. As they get to the surface - therefore in contact with the air - skins represent a serious risk factor for the stability of wine and for fermentation. When in contact with the air the skins tend to dry and, even worse, it can also develop vinegar and negative effects, such as mold, therefore damaging the wine. For this reason it is of fundamental importance the skins are always and completely plunged in the wine, by constantly keeping them wet and avoiding the contact with air. In order to avoid this inconvenience, it will be necessary to periodically “punching-down” the skins - two or three times a day, at regular intervals and for all the period of fermentation - consisting in plunging the skins by means of a stick or a similar tool. This operation ensures a better extraction of coloring substances and polyphenols from the skins, as well as favoring the oxygenation of yeast, therefore making it more active.

 The substances extracted during the maceration of the skins in the must, are essential for the color of wine and, in particular, the extraction of polyphenolic substances - tannins - give the wine a proper structure. The quantity of substances extracted from the skin depends on the type of grape, temperature and maceration time, therefore it will be paid proper attention, during the fermentation, to check the quantity of color and polyphenols, in order to remove skins at the proper time. When the desired quantity of color and polyphenols will be extracted - also before the end of alcoholic fermentation - we will proceed to the separation of the skins from the wine. Skins will be then pressed and the wine obtained from this operation will be added to the fermenting mass. It should be remembered this operation is done when the wine gets the desired quantity of color and polyphenolic substances, a condition which can also happen at the end of alcoholic fermentation as well as during this process.

 

After the Fermentation

 Alcoholic fermentation is over and the tumultuous bubbling of the wine has now reached its quiet, just like the sea after the storm. Despite the appearance would suggest the fermentation process is over, indeed the tumult is now replaced by other fermentative activities, equally important, just like the primary fermentation. Wine is an “alive” beverage, therefore in continuous evolution and in continuous change. Before tasting the result of our job, it will be necessary to do some and indispensable operations, of which the first one is the so called “first racking”, that is the separation of the wine from the solid parts which have sedimented during the fermentation. These solid parts, made of yeast residuals and solid substances found in the must, will be separated after the alcoholic fermentation in order to avoid their degradation with the risk of damaging the stability of our wine.


 

 When the alcoholic fermentation visibly diminishes its tumultuous activity, solid parts begins to sediment on the bottom and therefore it is now the moment to do the first racking. In general terms, the first racking is done when in the wine there are about 1-2% of residual sugar left - which will be subsequently fermented during the so called “slow fermentation” - however the time of the first racking is determined according to the type of wine to be made. Young wines, destined to an immediate consumption and allowed to macerate with the skins for four or five days, are racked at the end of fermentation, when in the wine are still found 3-5% of non fermented sugar. For quality red wines - however destined to an immediate consumption - and wines produced with overripe grapes, it is preferred to do the first racking at the end of the alcoholic fermentation, that is when there are no residual sugar left. Wines destined to long aging or however full bodied and structured wines, are usually racked after some days from the end of fermentation, therefore allowing the wine to further macerate with the skins - such as in case of red wines - and with lees, therefore giving a higher structure.

 During fermentation, it may probably happen the development of some negative smells - such as the one of sulphurated hydrogen, typically associated to the smell of “rotten eggs” - therefore it is always suggested to do the first racking “in contact with the air”, by favoring a strong oxygenation. The oxygenation of wine done during the first racking will also be useful to the “reactivation” of yeast, therefore favoring the so called “slow fermentation”, that is the fermentation of residual sugar and which is done in the days following the first racking. For the first racking we will need a flexible rubber pipe, which will be used to transfer the wine from the fermentation container to the one used for the keeping and aging, while avoiding to transfer solid parts and lees. During the first racking, because of the contact with the air, part of volatile sulfur dioxide will be lost and - despite it is replaced by combined sulfur dioxide - the total quantity of SO2 contained in the wine will diminish, therefore increasing the risks of degradation and oxidation.

 For this reason, at the end of the first racking it is always recommended to add a small quantity of sulfur dioxide - from 4 of 6 grams of potassium metabisulfite for every 100 liters of wine - in order to reintegrate the lost quantity. In case bad smells are still present after the first racking, it is suggested to proceed with another racking - still in contact with the air - in order to favor the dispersion of bad smells. Before proceeding with the first racking - and however before doing any racking - it is always suggested to check the stability and resistance of the wine, in order to adopt proper preventions. The easiest method which can also be used in home wine making is the so called “test of the air”, consisting in leaving a small sample of wine exposed to the air, that is by allowing it to be exposed to the effects of a critical condition. It will be enough to pour the wine to be tested in a glass - half a glass is enough - and to left it for one or two days to the air at room temperature.

 After one or two days, the wine is observed and checked: in case the color is not changed, there is no haziness and the taste did not become weak, then the wine has good qualities of stability and it is resistant, therefore we can proceed with the first racking - or with the racking - with no particular risks. In case the color of the wine has changed or it is observed some haziness, reduced limpidity, then the wine is affected by “oxydasic casse”. In this case it is necessary to postpone the racking and to add to the wine 10-20 grams of potassium metabisulfite for every 100 liters, according to the intensity of faults, and to repeat the air test after two or three days. In case in the wine are still noticed faults, it will be necessary to repeat the treatment with a half quantity and to repeat the air test until the wine has not become stable. In this case it is suggested to do the first racking with the least possible contact with the air - saved the case the wine has bad smells - as an excessive contact with the air can develop pretty serious faults.

 

Choice of Containers

 The type of container used for fermentation, keeping and aging of wine, plays a fundamental role. According to the type of wine to be made, in the many phases of vinification will in fact be used different type of containers, where the volume and the material used for the construction will play a fundamental role. Another essential role in containers used for the vinification is played by hygiene. It is of fundamental importance all the containers, before being used, offer hygienic conditions such not to negatively affect the organoleptic qualities of wine as well as its stability and health. Containers used in wine making are classified in two categories: inert containers and porous containers, made of wood. Inert containers - such as steel or cement vats and glass containers - do not alter the organoleptic qualities of the wine as they do not allow the exchange of the air with the outside, a characteristic which is typical in porous containers, such as casks, barriques and wood vats.

 All the type of containers can be used for the fermentation of wine, whereas only some of them can be used for the keeping and aging of wine. For the alcoholic fermentation of white wine are generally preferred inert containers, whereas for red wines can be used both inert containers as well as casks or wood vats. The fermentation in cask or in wood vat - which can also be used for white wines - because of the heat and the fermentative activity, favor the extraction of tannins and aromatic components from wood, which will be then passed to the wine. The quantity of components extracted from wood also depends on the age of the cask and on the number of times it has been used: the newer the cask the higher the quantity of components extracted. With time and with use, casks, barriques and wood vats will influence less and less the organoleptic qualities of the wine. For this reason in the commercial production of wine it is common the completely replace - or to use them for other purposes - casks and wood containers every two-four years.

 Every type of container offers both advantages and disadvantages which will be considered at the moment of the choice in according to the type of wine to be made. Wood containers - casks, barriques and wood vats - besides ensuring the essential exchange of air with the outside, indispensable factor for the aging of wine, will also give the wine their organoleptic qualities as well as ensuring a better isolation from temperature changes. A good isolation from temperature changes is also offered by cement tanks, which also have the advantage of being cheap and to be built according to the room needs of the cellar, however they do not allow the exchange of the air with the outside and they are therefore suggested for young wines or however for wines to be consumed within two or three years from production. Steel tanks are more expensive, offer very good hygienic conditions, however they are more sensitive to temperature changes and for this reason they need proper systems of thermoregulation. Fiberglass containers, very common in home wine making, offer the advantage of being cheap, however they are pretty sensitive to temperature changes. For small quantities can also be used glass demijohns, both for the fermentation and for the keeping.

 Before being used, containers must be scrupulously washed in order to ensure a good hygienic condition. Cement tanks, which must be covered inside with inert materials, are washed with a solution of hot water and 2% of soda. Fiberglass containers and steel tanks are washed with hot water. In all the cases the deposits or tartrates will be scrupulously removed. Brand new casks, never used or with repaired staves, are washed with a solution of hot water and 51% of soda, then must be scrupulously rinsed, allowed to dry and then will be burned one or two sulfur discs inside of it, according to the volume. Used casks, are cleaned with a brush in order to remove any deposit of tartrates, then washed with a solution of water and 10% of potassium metabisulfite. They are then scrupulously rinsed and some discs of sulfur will be burned inside, as mentioned above. In case the casks have stayed empty for a long time, before using them, it is better to make sure about their perfect tightness. In this case the casks are completely filled with a solution of water and 10% of potassium metabisulfite: in this way the staves are allowed to swell and to tighten any possible loss. After some days, the casks are then emptied and are therefore used the same treatment described for used casks.

 




 Events  Share this article   Share on Google+   Summary of Corkscrew column Not Just Wine 
  Corkscrew Issue 50, March 2007   
Making Wine: After the FermentationMaking Wine: After the Fermentation  Contents 
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