Vinification

The next stage in the creation of wine is vinification, the conversion of those grapes into wine. This is done once the grapes are harvested. Neither viticulture or vinification are better than they other, they complement each other. The grower should produce the best grapes he can from the vineyard and the winemaker must make the best wine he can from those grapes. In this context best will mean most commercially favourable. Many situations have the same person performing both jobs. The intinsic quality of any wine comes from the vineyard the grapes came from. A winemaker cannot make a good wine from bad grapes but a winemaker can make a bad wine from good grapes.

When it's been decided that the grapes have reached optimum ripeness in relation to the wine that is to be made, the date of vintage will be determined. Harvesting will then begin. In some areas a number of grape varieties are grown or a property may consist of a number of different parcels of vines there may be a spread of dates when the grapes achieve optimum ripeness.

Large wineries that purchase grape from a number of independant growers, and cooperative wineries, will also have to take the organisation of the grapes being recieved into account. Growers may recieve instructions to bring in certain grpes on certain days in order to spread the workload.

Constituents of the Grape.

The amount of sugar in the grapes determines the ripeness of the harvest. As the grapes ripen the density of the juice increases. By measuring the juice's density or "must-weight" the potential alchohol content can be arrived at.
A number of scales have been devised but the most often used are Beaume and Oechsle.. for comparison, the following table shows the Beaume and Oechsle scales alongside the potential alchohol.

Oechsle	Beaume	Potential Alc(% vol)
65	8.8	8.1
70	9.4	8.8
75	10.1	9.4
80	10.7	10.0
85	11.3	10.6
90	11.9	11.3
95	12.5	11.9
100	13.1	12.5
105	13.7	13.1
110	14.3	13.8
115	14.9	14.4

Must-weight is affected by other compounds within the grapes, not just sugar, so theoretical potential alchohol may differ from that achieved by the winemaker. Furthermore, the winemaking processes used will affect the final alcohol. For example, some alchohol will be lost during the manufacture of red wine fermented at high temperature. In general, 17 grams per litre of sugar will produce 1% alchohol by volume in white wines, but 19 g/l are needed for red.
The juice of a grape, contained in the pulp, is colorless with a few rare exceptions. If you peel back a black grape this can be easily seen. All the colouring material is in the skin, along with some flavouring constituents and tannins. On the outside of the grape skin is the waxy bloom that contains the yeasts needed to start the fermentation, and bacteria. There are two groups of yeasts; wine yeasts (Saccharomyces cerevisiae), which are anaerobic, (they can operate without oxygen, and wild yeasts,which need air (aerobic). The latter off-flavours in the final wine. Aceteobacter, is the most imortant bacteria present which will in the presence of oxygen , turn the wine into vinegar. The wild yeasts if uncontrolled, would start the fermentation process but die off at about 4% alchohol vol. The wine yeasts would take over, converting the remaining sugar to alchohol. This would then be destroyed by the acetobacter. Many of the functions of winemaking are concerned with controlling this natural progression.

Before the grapes are pressed, the stalks are generally removed . The role of stalks has diminished as time has gone by. In certain regions some growers still leave them in to add tannin to their red wine. Removing the stalks will damage the structure of the grape berry, so where white wine is made from red wine grapes the bunches will be left intact.

Gentle pressing of the grapes avoids the crushing of the pips thus avoiding the imparting of an unpleasant astringency that comes from them.

Pressing

The Development of the wine press.

Traditionally , all wine presses were vertical, with the pressure on the grapes coming from above through a screw. Horizontal presses have become more prvalent in usasge. Models such as Vaslin have the pressure come from the ends, again applied by way of a screw but can be controlled more exactly than in a vertical press. The latest preses (Willmes and Bucher) consits of an inflatable rubber tube within a perforated, horizontal stainless steel cylinder. here the pressure is gentle and gradual. A more delicate wine requires requires gentler pressing of the grapes and may indeed, be made from free run juice.

The volume of juice extracted from the grapes will vary from one variety to another and from one region to another. As a general rule, however, one kilogram of grapes will yield one bottle (75 cl) of wine.

Treatments

Chaptalisation
In some circumstances it can happen that there is insufficient natural sugar in the grapes for the wine to reach a satisfactory degree of alcohol. This is usually in cooler climates. When this condition arises then chaptilisation (also called must enrichment) may be carried out. This is the addition of sugar to the must , either before or during fermentation, to increase the alcohol content to the required level. This process is forbidden in many parts of the world, and is strictly controlled where it is permitted. If judiciously used , chaptilaisation can improve wines, can can also ruin them if abused.

Sulphur
A indispencible compound used in the winery is sulphur dioxide (SO 2). It acts as an antisceptic and an anti-oxident. The killing of wild yeasts and bacteria is now a widespread practice. These are present on the grape and their treatment with S0 2 before fermentation starts avoids the off-flavour that would otherwise be imparted into the wine.

Traditionally winemakers would cleanse their casks by lighting a sulphur candle in each one, which would give off So 2 gas as it burnt.

Sulphur dioxide is also useful after fermentation. Bulk wines will have SO 2 added to avoid oxidation and to kill any bacteria or yeasts present which would cause spoilage.

Sulphur can be added in the form of metabisulphite compound , as present in Camden tablets used in home brewing , or in gas form from pressurised cylinders.

Care must be taken not to use excessive amounts as this will result in an unpleasant smell and taste in the wine. Because of this the European Community has set strict limits on the amounts permitted in various types of wine, ranging from 160 milligrams per litre for dry red wines to 260 mg/1 for sweet white wines.

Yeasts
Once the grapes are crushed fermentation will naturally start. This is because there are yeasts present in the millions on the grpe skins and in the winery.
It is becoming more common especially in New World wineries, for the winmaker to select particular cultivated yeasts that are most suitable for the wine to be made. Cultured yeasts normally added in the form of dried powder, reduce the need to add So 2 and may be selected to give a particular character to the wine. Specially cultivated yeasts are essential in the production of certain wines. for example , the second fermentation in Champagne needs yeasts capable of operating at high pressure.

Other Adjustments
A particular region may or may not permit a number of other treatments. These include acidification of those wines lacking acidity, or deacidification of those wines with too much. Acidification is normally carried out by the addition of tartaric acid in powder form, although citric acid is sometimes used. In Europe, the process is limited to the warmer regions, but is common in many New World wineries. De-acidification is carried out by neutralizing excess acidity byt he addition of potassium bicarbonate. It is most common in cool climates. If there is insufficient tannin, this to may be added in the form of a powder, or by including some of the stalks in the vat, although this is less common in modern wineries than it was once. Legal controls exist for all these treatments.

Fermentation

Heat is also generated during fermentation, and this will need to be controlled, especially for white wines. During the fermentation , the temperature of the must in each vat will be monitored and recorded on a graph. If necessary the vat will be cooled by the se of a water-jacket or by pumping the wine through aheat exchanger. The density of the must is recorded at the same time on the same graph, as illustrated. The reduction in density shows the decrease in the sugar content and the increase in alcohol content.

One of the most important advances in modern winemaking is the temperature control during fermentation. From the moment that the grapes are brought in to the press-house, temperature's will be controlled as the character of a wine can vary considerably depending on the temperature at which it has been fermented.

More and more frequently, grape picking is done at night so the grapes arrive at the press-house cool. This is happening in hotter climates. In more marginal climates , however, such as Burgundy, the ambient temperature may be so low that fermentation will not start naturallly. in such a case the must has to be heated gently, often by passing warm water through a metal coil, either within the fermentation tank, or round it's exterior.
Red, rose and white wines are vinified differently, each using similar equipment but in a different sequence.

Red and Rose Wine Vinification
Black grapes are generally used to make red and rose wines. Picking the grapes in perfect condition is particularly important. The grapes cannot be affected by rot as this will lightgen the colour of the wine.

The classic treatment is for them to be destalked and crushed. The resultant mass is put into a vat where it is allowed to ferment.

Red Wine
With red wines the fermentation should begin at about 20 C, but will cease to function if the temperature reaches about 35 C. It is essential therefore that the temperature of the fermenting mass is controlled . The ideal temperature may very well vary from region to region and from grape variety to grape variety. For the Pinot Noir in Burgundy somewhere between 30 C and 32 C is perceived to be ideal. The temperature is higher for reds than whites to aid the extraction of color.

A fermenting vat of red wine will soon have a thick mass of pulp and skins on the surface if left to itself. The juice will take on very little color if nothjing is done about this. It is essential that therfore, that as much coloring matter be extracted from the mass as possible. There are various ways of achieving this they include:

Pumping over (remotage)
Most of the red wine is now produced by pumping over . This involves drawing wine off from the bottom of the vat and pumping it on the top, thus breaking up the crust. This is normally done twice a day.

Heating
If the grapes are heated at the start of fermentation, the skins release their coloring matter more freely, resulting in a very deeply colored wine. The danger of this thermovinification process is that it can give the wine a "soupy" taste.

Breaking up (foulage or pigeage)
In this the crust is broken up from above. Traditionally this meant men getting into the vat and trampling the crust down. This was a dangerous operation as there was always a liklihood that they might beovercome by the VO 2 being given off. Now, the same effect is achieved with paddles or rakes.

Rotary Fermenters
This is a modern technique where red wines are fermented in horizontal tanks which can rotate to bring the skins back in contact with the juice. To concentrate the colour and tannin in a wine it is possible to draw off some of the fermenting juice, thus increasing the proportion of solids to juice in the vat. This also leaves the producer with a quntity of rose wine'. This is now becoming more common in Burgundy, but was particularly used in California when there was a movement to produce the gutsiest of all wines, particularly Zinfandel.

Ideas about the lenght of vatting required have changed. It used to be thought that the longer the wine and skins were left together (maceration), the more color tannin and flavour would be extracted.
Color extraction rapidly at the beginning of maceration, sslowing up slightly as the fermentation continues; tannin is slower initially so longer macewration is required for wines destined for long maturation.
Current thinking suggests that there is no reason why skin contact should be continued once all the sugar has been converted into alcohol.

Typical maceration time might be six days for a wine with good color and moderated tannins, but twelve of more for A tannic wine requiring ageing. if the maceration time is limited to two days and the wine drawn off to ferment without the skins , a rose' wine, with very low tannin will result.

The length of time required to complete fermentation varies from area to area and grower to grower , lasting anything from one to three weeks. The objective with virtually all red wines is to convert all the sugar in the juice to alcohol.

Carbonic Maceration Aside from traditional method of fermenting red wines, there are a number of other techniques. Of these, one of the most widely practised is carbonic maceration. In this, complete bunches of uncrushed grapes together with their stalks, are placed in vats under a blanket of carbon dioxide. The fermentation begins within the grapes themselves, they ultimately burst and a more normal fermentation then takes place. This extracts color but not tannin, and the resultant wines are soft and full of fruit. They generally do not age well. The Beaujolais region in the south of Burgundy uses semi-carbonicmaceration for the bulk of it's wines.

There are half-way houses between the the traditional and carbonic maceration methods, and often wines made in the two ways are blended together before bottling.

Whichever vinification method is used , when the vatting has finished the free run wine (vin de goutte) is drawn off. What remains, the grape skins gorged with juice, is then pressed. This gives the press wine (vin de presse), most of which will be blended in with the rest and then either put into barrels , or back into the vat, to under go the secondary, or malo-lactic fermentation, and aging. The final pressing of the skins often yields wines which are too tannic and coarse to be used for blending and these will be distilled.

Rose Wine
There are essentially three ways of vinifying rose' wines. In the first the grapes are pressed directly and the juice is then fermented, as in white wines. Technically this produces a vin de gris. Most traditional roses' produced in the European Community are made by an abbreviated red wine vinification, with crushed grapes being macerated for one to three days before the pale colored juice is run off to continue it's fermentation without the skins. The third method, the saignee method, requires the grapes to be stalked , but not crushed, and vatted for 12 to 24 hours - the lesser the contact the paler the color. The juice is then run off and fermented without skin contact. Rose' wines are usually fermented in tank rather than cask and bottled young.

In the European Community, with the exception of Champagne, it is forbidden to make rose' wines by blending together red and white.

White Wine Vinification
White wines have to be treated with more care than reds as the danger of oxidation of the grapes is much greater. The grapes are pressed on arrival at the press-house as color and tannin are not required, though there may be two or three hours contact with the skins at low temperature to impart more flavour and fruit. The juice is drawn off from the press, either into vats, or into casks where it is allowed to ferment.

Normally, fermentation will take place at a lower temperature (usually between 15 and 20 C, sometimes even as low as 9 C) and over a longer period than red wine. This is to concentrate the fruit flavours of the wine and to avoid loss of freshness. Given that the fermentation reaction itself creates heat, this may well mean that the must will need cooling. In a modern winery, this is a straight forward process, for each vat will normally have it's own individual refrigeration/heating system.

If the wine is fermented in barrel the lees are often stirred up, to impart even more flavour to the wine. A number of winemakers are producing white wines fermented in new oak. Once the fermentation is over, the wine will be racked (transferred into clean casks) to avoid spoilage caused by over-long contact with the lees.A sweet white wine can be created in a variey of ways.

The best wines are made from grapes that are so rich in sugar, often as a result of concentration by botrytis, that the fermentation stops naturally when the yeasts have converted as much sugar into alcohol as they can.
This happens both in wines such as Sauternes and Tokaji, which have an Trockenbeerenauselese which can be as low as 7% vol.

If a fermenting must is filtered using a membrane filter, which is so fine that it removes all the yests, before the sugar has been consumed , a sweet wine will result. as not all the sugar has been fermented the wine will also be light in alcohol.

For lesser quality wines the yeasts can be killed before they have finished their work by the addition of SO 2.

In some countries, particulary Germany, medium-sweet wines are made by the addition of unfermented grape must or sussreserve. This is a sterile product made by membrane-filtering must before fermentation starts, or by dosing it with SO 2. Sussreserve is added to dry wine after fermentation to sweeten it and, in many cases, to balance the acidity.

A cheaper method, also caried out once the fermentation has been finished , is the addition of concentrated must. This is not used for high quality wines as the concentrated must tends to give the wines a "varnishy" character. The yeasts can also be killed off by the addition of alcohol, as in the production of Port, Vins Doux Naturels of France and other similar wines.

Malo-lactic Fermentation
During malo-lactic fermentation, lactic bacteria convert the tart malic acids (as in apples) into the softer lactic acids (as in milk). For red wines this fermentation is considered to be necessary and may be encouraged by keeping the temperature high and SO 2 levels low.

With many white wines, themalo-lactic fermentation is not permitted to take place, refreshing acidity being welcomed in most white wines. It is discouraged by the use of higher levels of S0 2.

Maturation

To survive medium or long term ageing the wines will need high levels of tannin, acidity or alcohol, but more importantly must have a high level of fruit.

The question of cask ageing is one for the winemaker to decide.
Generally, the better the wine the greater the need for barrels - and for new oak. They will add tannin to a wine and also soften out some of the other characteristics by means of a very slow oxidation. Factors that might well be taken into consideration when selecting new barrels are the source of the oak, the way it has been cut, aged and whether it has been "toasted' or not. Small casks have a more marked affect on the wine than large ones as a result of the greater ratio of wood surface to wine. The standard small cask is the barrique, which contains 225 litres, the equivalent of 300 bottles, or 25 cases. It has now been adopted by wineries in most parts of the world.

New oak adds an aroma and flavour of oak to the wine, usually identified by a smokey or vanilla character, and adds wood tannins. This effect diminishes as the cask gets older, so a one year old cask gives less flavour than a new one and by the time the cask is four years old very little flavour or tannin is added.

A declining scale of contribution that the vessel used for ageing makes to a wine might read something like:

Small new oak barrels
Second-hand oak barrels (one or two years old)
Large oak barrels
Neutral vats:stainless steel, epoxy, glass lined

Normally, a cask-aged red wine will spend a maximum of eighteen months to two years in cask before bottling. During this time the casks will be topped up (ouillage) regularly and racked every six months or so.
Before final racking, the wine will usually be fined (see below). To settle any suspension present.

While most white wines will have been fermented in vat, some will then be aged in cask for a short period of time. This is because of the extra flavours that the wood imparts to the wine. Sadly, there are now many short-cuts, such as addition of oak flavour, which can achieve the same effect. Most white wine is simply bottled young for early consumption. >br>

Fining

During the life of a wine in bulk too, a number of heavy particles will naturally fall to the bottom of the vat or cask. Wine will also contain a certain amount of lighter matter which would naturally remain in suspension. In order to clear this there are certain agents which when mixed with wine, will coagulate the suspension and cause it to fall to the bottom. Amongst such substances are albumen (egg white), diasmaceous earth (bentonite) and isinglass, as well as many propriety products. These agents combine with the suspension, forming heavier clusters of matter which settle under the effect of gravity. The process is known a fining, and may take place on one or several occasions during a wines life in bulk.

Stabilisation

Chemical Instability

Tartrates

The most common chemical instability leads to the formation of calcium or potassium-tartrate crystals, which look like sugar. White wines are particularly prone, with cold weather often the cause. this is natural and in no way affects the quality of the wine. However, because certain markets, particularly the United States and Japan, insist on wines remaining star-bright, many wines will be chilled in bulk when they are young in order that the tartrates are precipitated before bottling.

Casse
Casse is a term used to describe a number of chemical faults in a wine that give rise to haziness or a deposit, usually with off smells and flavours.
Technically, oxidation is a form of casse. Oxidation, or oxidic casse, is identified by an orange-brown color in the wine. It may be prevented with the use of SO 2 possibly with ascorbic acid or by physically preventing contact between the wine and oxygen. It is very difficult to cure.

It is possible that the proteins in a wine may be unstable and give rise to a casse, in this case a grey haze in the wine, but there is usually no associated off smell or taste. Fining with bentonite should prevent this, and may cure it.

Other cases result from over high levels of metals, particularly iron and copper, though better cellar hygiene and equipment means these are less of a problem now. Iron produces a grey deposit and a smell of bad eggs; copper produces an orange-brown color and a musty smell. The most common cure for both iron and copper casse is what is known as "bluefining", using potassium ferrocyanide. As this is potentially dangerous the treatment must be carried out by a qualified chemist.

Microbiological instability
Micro-organisms-yeasts, and especially bacteria are responsible for a number of problems as well as desirable reactions in wines. Sometimes it is simply a question of timing, as in the case of a further alcoholic fermentation after a wine has been bottled. Other potential problems acetic spoilage, caused by aerobic acebacter converting the ethanol in the wine to vinegar. This can spread from one cask to another so needs to be prevented by the addition of suitable doses of SO 2 which combines with oxygen and renders the acetbacter inoperative.

Wines may also suffer from rod bacteria, although this is now rare due to improved cellar hygiene. There are four forms of rod bacteria infection; tourne, giving a dull appearance and mousy smell, graise making the wine viscous and oily, amertume, causing bitterness and loss of color, and lactic taint, again showing as amousy smell and a turbid wine. All of these are prvented by the use of SO 2 and sterile bottling.

One way of preventing such unwanted problems is by killing the micro-organisms using SO 2 or heat. Pasteurisation, used mainly for red wines, is an example of the latter. This is generally achieved by a "flash" system , which heats the wine to a temperature of 95 C for 1 or 2 seconds only.
This is widely used amongst the larger producers in areas such as Beaujolais, where large volumes of wines of consistent quality are needed.

A more gentle method of eliminating unwanted micro-organisms, and certainly one that does less harm to a wine, is physical removal by filtration to create a "sterile" wine. This can be done at normal temperatures, and will usually be part of the bottling process.

Filtration

Most wine will be filtered through a plate filter which will remove any unwanted particles from the wine. Those which are light in alcohol, or have some residual sugar, are more prone to spoilage and often will be sterile filtered using a membrane, or cartridge, filter which acts as a sieve that is so fine as to be able to remove both yeasts and bacteria. As the cartridges are easily blocked, the wine will previously have been plate-fitered to remove large particles.
Sterilising grade membrane filters give a wine that is totally free of any micro-organisms, so it is important to avoid later contamination by ensuring complete sterility of the bottling lines, bottles and corks.

Bottling

As this is the last stage in the active treatment of a wine, it is essential that all the efforts that have been taken so far should not be wasted at the last moment.

Bottle Aging
For a period of time after a wine has been bottled, it can suffer from what is known as "bottle sickness". This can lead to it showing badly.

The majority of wines are bottled for immediate consumption. However, there are many which will then improve after many months or years further ageing in bottle: for example, Vintage Port may not reach it's peak until 30 years after bottling. It is essential that this ageing time be spent undisturbed in a dark cool place with a constant temperature (preferably about 13 C). The bottles should be stored lying on their side, so that the corks remain moist to provide the optimum seal.

NEXT