Chapter 3: The winery--from grapes to bottle.
As mentioned in the previous chapter, wine is simply grape juice that has been fermented by yeast. Although this definition is quite simple, in the more than 6,000-year history of winemaking, wine production has evolved into a number of complex procedures that produce a variety of wines. Table wine is a wine designed to accompany food. It is produced in numerous forms, both red and white, and is the most common type of wine consumed in the United States, making up over 90 percent of the market (Adams Beverage Group, 2004). A table wine is a still wine (a wine without effervescence) and is also a relatively dry wine (without sweetness) having a moderate alcohol content of about 11 to 15 percent. To achieve this percentage of alcohol content, grapes are picked between 22 and 25 degrees Brix, or [degrees]Brix (the percentage of sugar by weight). In the United States, a wine must be less than 14 percent alcohol to be labeled a "table wine." This is an arbitrary number that was chosen for reasons of tax collection; wines with a higher alcohol content are taxed at a higher rate. The exact alcohol content has little to do with the true definition of being a wine made to complement food, and there are many table-style wines that are bottled at over 14 percent alcohol. Some table wines are also made with a small amount of residual sugar in an "off-dry" style.
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The Process of Fermentation
Fermentation is the process of yeast (unicellular or one-celled fungi) (Figure 3-1) converting the sugar in grape juice to alcohol and carbon dioxide, releasing some heat during the process. Yeast ferments sugar to produce energy to sustain life and reproduce. Other microorganisms can do this but yeast ferment with the most efficiency and can survive in the higher alcohol at the end of fermentation (Figure 3-2). The species of yeast that is best suited for winemaking is called Saccharomyces cerevisiae. The name Saccharomyces is derived from the Latin sugar fungus, while cerevisiae refers to grain. This is not surprising because the most common use of Saccharomyces cerevisiae is in bread making. When bread dough rises, it is from the bubbles of carbon dioxide that are produced inside the loaf during fermentation. Alcohol is also produced during bread making but it is baked off while the loaf is in the oven. This is what gives baking bread its distinctive smell. While the yeast used for winemaking and bread making is the same species, different strains are used which are adapted for their individual roles.
While this formula looks simple, it is actually a biochemical pathway with 12 separate reactions that are controlled by different enzymes in the yeast (Figure 3-3). The rate of fermentation is affected by a number of factors, including:
* temperature. The warmer the juice, the faster it will ferment; however, at temperatures above 100[degrees]F (38[degrees]C) yeast will die off.
* acidity. The higher the concentration of acid (lower the pH), the slower the rate of fermentation.
* nutrients. If the juice is low in nutrients, the yeast may not be able to ferment to dryness.
* alcohol. At higher concentrations, 13 to 16 percent depending on strain, yeast begin to die.
* sugar. Although sugar is required for yeast growth, if the sugar concentration is greater than 30 percent, it inhibits yeast growth.
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Winemakers use these factors to control the fermentation and make different styles of wine. As an example, Port wine is made by adding brandy to fermenting wine to kill the yeast before it can ferment to dryness. This way a stable, sweet wine can be bottled without further risk of fermentation.
Wine was made for thousands of years before anyone knew how fermentation worked or that there were such things as microscopic organisms called yeast. The conversion of grape juice into wine was considered a miracle of nature. Although early winemakers did not understand the mechanism, they knew how to use fermentation to produce good wine. There are still a few wineries that use this method of fermentation with natural or "wild" yeast to make wine. The winemakers at these wineries feel this method can give their wine more complexity, but there also is a higher risk of off-flavors or an incomplete fermentation. Today, most winemakers use commercially available strains of yeast that have been isolated from different wineries and manufactured for sale. These yeasts are usually sold in an "active dry" form that has a similar appearance to bakers' yeast, and they give the winemaker a clean, efficient fermentation with no off-aromas.
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Red Wine Crush and Fermentation
The harvest is the busiest time of year at the winery because the grapes must be harvested and processed as soon as they reach their peak of flavor. The weather conditions set the pace of harvest and it is not uncommon for winery workers to be on the job 12 hours a day for 7 days a week. Once the grower and the winemaker have determined that the grapes have reached their optimum ripeness and flavor, they are picked and brought to the winery. When the crop arrives at the winery it is weighed, inspected, and analyzed before being processed (Figure 3-4). If the grapes are being purchased and are not grown on the winery's estate, the results of inspection are very important. This is because grape contracts between growers and vintners often include bonuses and penalties that depend on the analysis at harvest and the overall quality of the fruit. Particularly at larger wineries, this inspection and analysis is performed by an independent third party to avoid conflicts of interest.
After the grapes are weighed and inspected, they are brought to the receiving hopper and unloaded. At the bottom of the hopper, there is either a screw or a belt conveyor that is used to transport the fruit to the stemmer-crusher (Figure 3-5). The stemmer-crusher has two functions: first it takes the berries off the stems, and second it breaks the berries open to release the juice. Stemmer-crushers are made up of a perforated stainless steel cylinder or drum that is 1 to 4 feet (0.3 to 1.2 meters) across. The perforations are holes that are large enough to let the individual grapes through, but not whole clusters or stems. Inside the cage is a set of bars that are arranged in a helix pattern. When the crusher is started, the bars begin to rotate at several hundred revolutions per minute (RPM), while the cage rotates at a much slower rate. The clusters of grapes enter in through the back of the cage and, when they come in contact with the bars, the berries are knocked loose and fall through the holes in the cage. The stems, once they have lost their grapes, are pushed out the front of the machine by the helix pattern of the bars (Figure 3-6).
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After the berries are destemmed, they fall to the second part of the machine--the crusher. The crusher is a set of rollers designed to break open the berries and release the juice. In modern crushers, the gap between the rollers can be adjusted to provide a greater or lesser degree of crushing. On some models the rollers can be removed entirely to allow whole berries to pass through. The mixture of approximately 80 percent juice, 16 percent skins, and 4 percent seeds produced by the crusher is called must. At this point, the must is liquid enough to be pumped to a tank for fermentation.
In modern wineries fermentation tanks are most often made of stainless steel (Figure 3-7), although vats made of wood or concrete are also still in use. The tank is filled to three-quarters capacity to allow room for expansion during fermentation and the must is analyzed and adjusted, if necessary. Usually, with the exception of the preservative sulfur dioxide, the compounds that are added to adjust the must, such as sugar, acid, nutrients, and yeast, are natural and already present in the must to some degree. Additives to wine are regulated and vary from region to region. For example, it is legal to add sugar to must in France but not acid, while in California the opposite is true. This is not a hindrance, however, because grapes grown in California seldom need additional sugar and French musts seldom need additional acid.
When the yeast is first added the must is homogenous; however, once fermentation begins, the carbon dioxide that evolves causes the skins to float to the top of the tank and form a cap (Figure 3-8). In large tanks, the cap is several feet thick and very firm. The juice from most red wine varieties is clear; therefore, to produce a red wine it is necessary to extract the red color out of the skins. If the skins are in a cap that is floating above the juice, very little extraction will take place. To combat this, the cap is mixed into the juice several times a day. There are many ways to do this, and the manner in which it is done, and the frequency, have a major effect on the overall style of the wine being made. If a cap is mixed in vigorously, and frequently, the result will be a wine with more color, body, and astringency than one with a more gentle treatment.
METHODS OF CAP MANAGEMENT
Punching down (Figure 3-9) is the oldest, simplest, and most gentle method of mixing the cap of skins and the juice. A punch-down device is used to press down the cap into the juice. Done by hand, it works well on smaller tanks with an open top. In larger tanks, pneumatically powered plungers are used.
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Pumping over (Figure 3-10) is the method by which the juice is taken from beneath the cap and irrigated over its top. As the juice percolates through the skins it extracts the color and flavor, similar to the way a drip coffee maker uses hot water to extract flavor from ground coffee.
Rotary fermentors (Figure 3-11) are the most modern and least labor-intensive way of dealing with the cap. They are large horizontal tanks that have fins along the inside, similar to a cement mixer, and when they are rotated, the cap is rolled over into the juice. The main advantage of rotary fermentors is that they make it very easy to extract the skins after fermentation by opening the door at the end of the tank and rotating it. The disadvantage is their high cost.
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From the time the yeast is added, the fermentation usually takes about 1 to 3 weeks. This depends on several factors: the amount and type of yeast added, the nutrients in the must, and the temperature. Most red wine fermentations will peak at about 85[degrees]F (30[degrees]C); at this temperature there is good color extraction without the yeast becoming too hot. When the yeast has fermented all of the sugar in the must to alcohol or, in the case of sweet wines, as much sugar as the winemaker wants to be fermented, then the must is considered wine. At this point, the juice is drained off the skins and the skins are removed from the tank for pressing.
PRESSING THE SKINS
In red wines, when fermentation is complete and the winemaker is satisfied with the flavor extraction, it is time to separate the wine from the skins. The majority of the wine is simply drained out of the tank by gravity. The remaining wine, 10 to 20 percent, is held within the skins still inside of the tank. The skins are then removed and loaded into a press, which squeezes out their remaining liquid. The removal of the skins from the fermentation tank is one of the most labor-intensive aspects of winemaking (Figure 3-12). Great care must be taken when entering a tank that has just finished fermentation due to the danger of asphyxiation from the residual carbon dioxide. Before the tank can be entered, it must be properly ventilated and the atmosphere tested to make sure it is safe.
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There are a number of types of presses, but they all work in the same manner. Force is applied to a layer of skins against a screened or slatted surface which allows the juice or wine to drip through, but holds the skins and seeds back. After pressing, the compressed layer of skins is called a cake. To extract the maximum amount of liquid from the skins it is necessary to break up the cake and re-press it a number of times at progressively higher pressures. The first wine to come off is usually combined with that which was dejuiced from the tank and is called the free run. As the cycles of pressing continue, the quality of the juice diminishes and becomes more astringent and bitter. Often, the wine that is removed at the end of the press cycles is kept separate from the free run and is called the press fraction. The young wine is then collected in a sump at the base of the press before being pumped into a receiving tank. After the skins dry they are called pomace or marc (the French term for pomace), and are removed from the press and used for compost in the vineyard.
The basket press is the oldest and most simple design (Figure 3-13). It is a vertical cylinder made of slats of wood arranged with small gaps in between. The fruit is loaded into the top and a plate is pushed down by mechanical means, which causes the juice to drip out through the gaps in the slats. Traditional basket presses are gentle but require the cake to be broken up by hand in between press cycles. More modern basket presses are made of fiberglass and mounted horizontally; the cake can then be both broken up and unloaded by simply rotating the press.
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Another type of press uses air pressure, or pneumatics, to squeeze the juice out of the skins. There are a number of designs for pneumatic presses; one of the most common is the tank press. Tank presses are cylindrical steel tanks that are 3 to 8 feet (1 to 2.4 meters) in diameter and are mounted horizontally. On one side of the interior there is an inflatable bag or membrane, and on the other side is a series of perforated screens or channels. Once the press is loaded with grapes and the door is closed, it rotates so that the screens are down and the bag is above. The bag then inflates, squeezing the skins against the screens and removing the juice. There is less chance for contamination or oxidation with tank presses because they extract the juice inside the press. Their efficiency and gentleness toward the grapes make them the workhorses of most modern wineries. Yield after fermentation is typically about 170 gallons of wine per ton of grapes (700 liters per metric ton).
After pressing, the wine is pumped to a tank in the winery cellar for storage. At this point the new wine is very turbid and full of suspended solids that are primarily yeast cells and particles of grape skins and pulp. After several days, the suspended solids begin to settle out to the bottom of the tank, forming a layer of thick, mud-like material or dregs called lees. After a week or two, the clean wine is decanted off the layer of lees in a process called racking. This process of settling and racking can be done once, or repeated several times, to clarify the wine before it is transferred to the aging cellar and placed into barrels.
White Wine Crush and Fermentation
It is no surprise that white wines are made from white grape varieties. However, since the juice of most red grapes is colorless it is also possible to make a white wine from red grapes, as is done with White Zinfandel and Blanc de Noir sparkling wine. So, white winemaking is defined not only by the color of the grapes that are used but also by how they are processed (Figure 3-14). The major difference between white and red wines is that reds receive most of their flavor from the skins and whites get their flavor from the juice. Therefore, in processing, the most important difference is that red wines are pressed after fermentation and white wines are pressed before. Because the flavor of white wines is not as dependent on what is extracted from the skins, the grapes are usually picked early in the morning and brought to the winery while they are still cool in order to preserve their fresh fruit flavors.
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White winemaking begins in much the same way that red winemaking does--the grapes are picked, weighed, inspected, and delivered to the receiving hopper in much the same way they are for red wine production (Figure 3-15). However, since the delicate character of white grapes is more sensitive to warm temperatures than red grapes, a special effort is made to pick white wine grapes in the morning when temperatures are cooler and to quickly transport them to the winery. Once the grapes are unloaded, red and white winemaking techniques diverge and for white wine production the juice is separated from the grapes before fermentation. The winemaker has several options on how to accomplish this. The fruit can be (1) crushed and pressed; (2) it can be crushed, dejuiced, and pressed; or (3) it can be whole-cluster pressed.
In the first option, the grapes are destemmed and crushed and the must is pumped into the press for the juice to be separated. In the second option, the must is dejuiced before being loaded into the press. This is done by having a slotted screen to drain the juice inline on the way to the press. A more gentle method of draining the juice is the dejuicing tank. These tanks are mounted above the press, and the must is pumped into them directly from the crusher. A screen is located on the inside of the tank and the force of gravity helps the grape juice to drain through it. The third option of processing white grapes, whole-cluster pressing, is also the most gentle. In this method, the stemmer-crusher is bypassed entirely and the whole clusters are loaded directly into the press. This minimizes the amount of skin contact the juice receives, and since the grapes are not macerated by the crusher, it produces a juice with lower solids and a more delicate flavor. Whole-cluster pressing, however, is more difficult and expensive, because it requires a larger press and more time to load as whole clusters of fruit do not dejuice as readily as crushed fruit.
After pressing, the juice is pumped to a settling tank in the fermentation cellar. In white grape pressing the difference in quality between free run and press juice is even greater than it is with red wines, so the press juice is usually kept separate from the free run. The juice is kept cool, at around 50[degrees]F (10[degrees]C), and held in the settling tank for 12 to 72 hours to allow the lees to form. It is necessary to separate the juice from the grape solids, or primary lees, to avoid the production of undesirable flavors during fermentation. After settling is complete, the clean juice is racked off into the fermentation tank (Figure 3-16) where it is adjusted with yeast and fermentation additives, if needed. Similar to red winemaking, the tank is not filled to capacity in order to allow room for the foam that forms during fermentation. White wine fermentations take place at a cooler temperature, 45[degrees] to 60[degrees]F (7[degrees] to 15[degrees]C), because there is no need to extract color from the skins as in red wine fermentations. The cooler temperature helps the juice to retain its fruity aromas. Because it takes place at a cooler temperature, white fermentations take two to three times longer than red fermentations, about 3 to 6 weeks. After fermentation, the new wine is racked off the yeast lees into a holding tank in preparation for aging and processing.
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Some white wines are transferred to barrels just as they are starting to ferment. Barrel fermentation of white wine gives it a distinctly toasty aroma and is very popular with Chardonnay. After the fermentation is finished, some of the barrels are used to top off the rest of the lot and the wine is left in contact with the yeast lees at the bottom of the barrel. This technique of aging is called sur lie (French for "on the lees"), and it gives the wine more of a yeasty-bready aroma and more viscosity. The young wine can be left sur lie for many months; sometimes the yeast is periodically stirred to intensify the character.
Barrels and Aging
The first coopers, or barrel makers, were the Romans over 2,000 years ago (Jackson, 2000). The Romans used barrels to store and transport a variety of goods, including wine. Winemakers soon discovered that storing wine in barrels had positive effects on the wine's flavor and body. The qualities that barrel aging gives to a wine are so positive that barrels are still used for winemaking today, long after their other uses have been discontinued. Although there has been some mechanization, barrels are still made by hand in the method they have been for hundreds of years. There are two types of reactions that take place during aging: the wine undergoes a slow oxidation and it absorbs flavor components from the wood. Both of these make significant contributions to a wine's flavor. Aging a wine in small, 60-gallon (225-liter) barrels is both expensive and labor intensive, but the positive effect that barrel aging has on wine makes it worthwhile (Figure 3-18).
Barrels can be made out of many types of trees, however, oak is the chosen wood for winebarrel production. In addition to being strong and durable, it is also nonporous so the barrels will not leak (Figure 3-19). Most importantly, it has excellent flavor and aroma compounds that are extracted into the wine during storage. Although oak is the wood of choice for winemaking, there are many different types of oak from which to choose. The two major categories of oak are European and American. There are two species of European oak that are used for making wine barrels: Ouercus sessilis and Quercus robar, and they are grown throughout France and central Europe. European oak is known for giving wine a rich, toasty vanilla aroma. In the United States Quercus alba, or white oak, is used for barrel making and has a stronger, more woody flavor than European oak. Beyond the type of oak used, a barrel's flavor varies depending on the forest the wood is from, how the wood is seasoned, and the various methods of production that different coopers use. This variety in styles gives winemakers a wide selection of flavors that they choose to put into their wine by aging.
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Much of the flavor obtained from aging wine in barrels comes from what is extracted out of the oak, however, the softening of the wine's texture that comes with aging is due to the process of slow oxidation. Oxidation can be a vintner's enemy, spoiling the wine's aroma and color as well as promoting the growth of bacteria that produce vinegar. Oak has the quality of being semipermeable to oxygen, allowing it to be incorporated into the wine at just the right rate. A small amount of oxygen in an aging wine helps tannin molecules to polymerize and settle out, softening a wine's body and making it less bitter. Furthermore, a small amount of alcohol and water in the wine can evaporate through the oak of the barrel. This evaporation causes the remaining wine in the barrel to become more concentrated with acid and flavor. From time to time, the ullage (headspace in the barrel) that is produced by this evaporation must be displaced by topping the barrel up with some wine from the same lot. The period of time that a wine spends in oak depends on the tastes of the winemaker and the body of the wine being made. A big-bodied red such as Cabernet Sauvignon or Syrah may need 2 or more years in oak before it has sufficiently mellowed for bottling. A fruity, light-bodied wine like a Beaujolais Nouveau or Gewurztraminer may be bottled with little or no oak aging. Wine can also be aged in stainless steel tanks or after it has been bottled. Under these conditions there is much less exposure of the wine to oxygen than there is in barrels, so the aging process is slower and has less of an effect on the flavor of the wine than barrel aging. In addition, during tank or bottle aging there are no flavor compounds being extracted into the wine from oak. Some wineries place oak wood in stainless steel tanks to get the flavor of the wood without getting the aged quality of barrel storage.
Finishing a Wine
After aging is complete, the wine is pumped out of the barrel and sent to the tank cellar for preparation for bottling. Wines can be bottled from a single fermentation lot but more often different lots are blended together (Figure 3-20). Blending can combine lots from different vineyards, even different regions and varieties, each with its own attributes. The art of blending lies in putting different combinations of these lots together in trial blends to find the combination that has the most balance and complexity. After the favorite trial blend is selected, its proportions are used to assemble a bottling blend in the cellar. Having a wide selection of wine lots with different flavors gives a winemaker many options to fine-tune the blend and achieve the desired style. Sometimes winemakers will blend before or in the middle of the aging process to give the blend time to harmonize in the barrel. After the blend is selected, two more steps must be completed before wine is ready to be bottled: clarification and stability. Clarification produces a wine that is brilliant and free of suspended solids, while stability operations are performed to ensure that a brilliant wine stays so. These operations are closely linked, and often one will complement the other.
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The simplest and most gentle form of clarification is settling and racking. As wines age in barrels, particles that are suspended fall out and accumulate at the bottom of the barrel. If the wine is carefully pumped out, the solids remain behind, sending a clean wine to the tank. Two more active methods of clarification are fining and filtering. Fining is the process of adding a compound called a fining agent to the wine that will react with compounds in the wine causing the two materials to combine and become insoluble. After the wine settles, the fining agent and the wine component that it removed are left behind in the lees when the wine is racked. Most fining agents are proteins although some, such as bentonite (a type of clay) and carbon, are inorganic. Fining not only helps to clarify and stabilize a wine, it can also affect the flavor. A classic example is egg white fining whereby egg whites, which contain the protein albumin, are added to a red wine. The albumin reacts with tannin molecules, causing them to drop out and make the wine softer in character.
Another fining agent that is used for clarity and stability is bentonite. Bentonite is commonly used in white wines to make them protein or "heat" stable. All wines contain some residual grape protein; this protein can denature (lose its shape) over time and become insoluble. If this happens after the wine is bottled, it will form a milky haze on the bottom of the bottle. To combat this, bentonite is added to white wines to remove the protein, and in the process it also helps to clarify the wine. Red wines have a much higher level of tannins. Since tannins react with proteins in a manner similar to bentonite, it is seldom necessary to fine with bentonite to make red wines protein-stable.
In addition to protein or "heat" stability, a wine is also "cold" stabilized to remove excess potassium bitartrate before bottling. Potassium bitartrate, or cream of tartar, is a salt comprised of two natural constituents of wine: potassium and tartaric acid (Figure 3-21). Potassium bitartrate is semisoluble and forms crystals over time, especially under cold conditions. These crystals will form in bottles or in tanks and have an appearance of ground glass. To avoid an excess of tartrates crystallizing in the bottle, wines are chilled in the cellar to just above the freezing point. The crystals then settle to the bottom and the walls of the tank (Figure 3-22).
Filtering is another way to obtain clarity in a wine prior to bottling. There are many types of filters designed for different winemaking applications (Figure 3-23). They all work by using pressure to force the wine through a porous substance that allows the liquid to go through but holds solid particles back. Filters are available in many grades of "tightness" that retain larger or smaller particles. Filtration is very important when making a wine that has the presence of residual sugar or malic acid. In such cases, if all of the microbes are not removed before bottling, they can begin to ferment in the bottle and spoil the wine. In any case, there are no human pathogens that can tolerate the alcohol in wine, so it is important to keep out microbes only because of their effect on wine stability and quality. Most winemakers use some form of fining or filtration to ensure the quality of their wine, however, others prefer a wine that is unfined and unfiltered. The philosophy here is that although a wine that is not fined or filtered may be less brilliant and less stable, it retains more of its natural flavor. While there is some truth to this argument, if fining and filtering are properly handled, they will have very little effect on a wine's flavor.
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Bottling, the final step in winemaking, must be done with great care because it is not easy to rectify mistakes after the wine is in the bottle. Before bottling, the wine is analyzed and checked for stability one final time and any necessary adjustments are made. The wine is then sent to the bottling room where a filler machine distributes it to the bottles (Figure 3-24). Immediately after being filled, the bottles are corked or capped to protect the wine from contamination. The bottles are then sent to a capsule machine to have a capsule applied to cover the neck and the cork. The final steps of applying the label and packing the bottles into cases then take place. Bottling is some of the roughest treatment a wine will receive and can leave a wine with less fruity aromas and body for a period of time. This condition is called bottle shock, and will go away if the wine is allowed to have some bottle age before consumption. While this is a real condition, bottle shock is often used as a scapegoat for anything a winemaker does not like about a new wine.
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Sparkling wine is defined as wine with bubbles or effervescence (Figure 3-25). It was first developed in the Champagne region of France in the 1700s, and was the result of two seventeenth-century winemaking inventions: the cork and the wine bottle. These innovations provided, for the first time, an airtight package for wine. Inadvertently, young wines were bottled before they had finished primary fermentation. Because of the tight seal, when the wines finished their fermentation in the bottle, the carbon dioxide was trapped inside, giving them effervescence. Over the next hundred years this accident was developed into the elaborate procedure used to make sparkling wine called methode champenoise, or the Champagne method (Figure 3-26). There are other processes used to make sparkling wine; however, the original methode champenoise is still considered to yield the highest quality product. The term "Champagne" refers to sparkling wine made in the Champagne region of France. In the United States, "champagne" is often used as a generic term to mean any sparkling wine, and it is legal to use the term on the label as long as the region of origin is listed (e.g., "California champagne").
Since the Champagne region is very cool, the grapes used for making sparkling wines are early ripeners. Pinot Noir, Chardonnay, and Pinot Meunier are three of the most common grapes used for sparkling wine; in California, the Pinot Blanc grape is also popular. The grapes used for sparkling wine are picked even earlier than those used for still wines for several reasons. The base wine used for sparkling wine should be low in alcohol and should not have a lot of varietal character. This is because the secondary fermentation will increase the alcohol content, and the finished wine should exhibit the flavors produced from the methode champenoise process. Furthermore, the grapes are handled very gently during picking and pressing to avoid extracting too much flavor or color from the skins. Press cycles for sparkling wine are longer and more press fractions are taken to ensure the best juice is kept separate. After fermentation, the wine is racked and stored until blending.
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In the winter following harvest, the winemaker tastes the various lots of wine produced and puts together the base blend called the cuvee. Cuvee is a French word that translates literally to "tub full" or "vat full." The cuvee is low in color and alcohol, but high in acid, and it takes considerable talent as a taster to see how the flavors in the cuvee will translate into the finished wine. After the blend is made, it is bottled with a small amount of sugar and actively fermenting yeast, and sealed with a crown cap. The wine is then stored in a cool, dark place during the fermentation in the bottle. As the yeast ferment, they produce about 1.5 percent more alcohol and about 90 pounds per square inch (6 atmospheres) of carbon dioxide. The bottles used are much heavier than those for still wine in order to hold back the pressure; they are also dark green because sparkling wine will develop off-flavors if exposed to excessive light. After fermentation, the bottles undergo tirage, whereby they are aged on the yeast cells for a period of several months to many years depending on the style of sparkling wine being made. During this time, the yeast cells begin to break down in a process called autolysis, which is what gives methode champenoise sparkling wines their unique flavor.
After tirage, it is necessary to remove the yeast from the bottle before the wine can be finished. The bottle is taken from storage, mixed to loosen the yeast from the sides of the bottle, and placed in a riddling rack. Riddling is a process used to accumulate the yeast at the end of the neck of the bottle. The bottle is placed horizontally in the riddling rack and every day it is twisted and pushed back into the rack at a slightly steeper angle. After several weeks, the yeast has settled at the end of the neck and the bottle is upside down, or sur pointe. Hand riddling is still practiced at some wineries but at most wineries the process is now done by machines. Following the riddling process, the yeast is ready to be removed by disgorging (Figure 3-27). The bottles are chilled to just above the freezing point and placed upside down in a brine bath to freeze the wine in the neck of the bottle. This traps the yeast, and when the crown cap is removed, the pressure of the wine expels the plug of frozen wine, taking the yeast with it. The bottle is then topped off with a small amount of base wine called dosage. Since sparkling wine is quite sour, the dosage often has a small amount of sugar to balance out the acid. The bottle is then finished with a wide-diameter agglomerate cork that is only inserted halfway to give it its mushroom shape. Sparkling wine produced by methode champenoise is labeled as such or as "fermented in this bottle."
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Other Methods of Sparkling Wine Production
Although the finest sparkling wines are made by methode champenoise, this accounts for only a small portion of production. The majority of sparkling wine is made by the Charmat process or "bulk" process developed by the French winemaker Charmat in 1907 (Figure 3-28). In the Charmat process, instead of having the secondary alcoholic fermentation take place in the bottle, it takes place in large steel tanks that are specially designed to withstand the pressure produced by fermentation. After fermentation, the wine is racked off and the yeast is filtered out under pressure. Once the dosage is added, the wine is bottled and usually sealed with a plastic mushroom-shaped cork. The ability to filter the yeast out saves the effort of riddling and disgorging, making these bulk-processed sparkling wines much less expensive to produce. Without the extended time on the yeast during tirage however, these wines do not have the same character as those produced by methode champenoise. The grapes that are used for the Charmat process are typically less expensive varieties such as Chenin Blanc and French Colombard.
There are two other methods used to make sparkling wine: the transfer method and artificial carbonation. In the transfer method, the cuvee is fermented in bottles and aged in tirage for a time. At the end of tirage, the wine is transferred from one bottle to another, being filtered in the process. Sparkling wine made this way is labeled "fermented in the bottle" instead of "fermented in this bottle." The transfer method, because it incurs extra expense without adding significantly to the quality, is not as popular as the methode champenoise or the Charmat process. In artificial carbonation, a still base wine is injected with carbon dioxide, carbonating it before serving, much the same way a soda pop dispenser works. These wines are usually served at large banquets and have little of the qualities of natural fermented sparkling wine.
There are multitudes of unique dessert wines that are produced throughout the world's winemaking regions. Dessert wines are made with appreciable sugar and often have higher alcohol to stabilize the wine and prevent it from fermenting in the bottle. Dessert wines make an excellent dessert in themselves, can be offered as a digestive after a meal, or can be a complement to a sweet dessert course. Although the classic definition of a dessert wine is a wine that is sweet, for purposes of taxation the United States Government classifies all wines that are fortified with additional alcohol as "dessert wines" whether they are sweet or not, and they are taxed at a higher rate than table wines. We will examine the production methods used in some of the most common types of dessert wines: late harvest, Port, and Sherry.
Late-harvest wines are made from grapes picked at a much higher sugar level than grapes used for table wines. Through photosynthesis grapevines can ripen the crop up to about 28[degrees]Brix, while late-harvest wine grapes are frequently picked at 35[degrees]Brix or more. Late-harvest wines achieve this higher level of sugar concentration due to the fruit partially dehydrating on the vine. Under the right conditions, water will evaporate through the skin of the berry, concentrating the sugar that is left behind. This high sugar means that the yeast will have a difficult time fermenting due to the combined inhibitory effects of alcohol and sugar concentration. Late-harvest fermentations progress at a very slow rate and are unable to ferment to dryness. When the fermentation eventually slows to a stop, a microbial stable, sweet wine is produced.
This dehydration is increased by an infection of a mold that is usually considered a vineyard nuisance, Botrytis cinerea or "noble rot" (Figure 3-29). This mold is a common problem in vineyards and is normally discouraged by applying sulfur dust; however, under the right conditions with the right varieties, it has the ability to make some of the world's best wines. Botrytis cinerea infects ripe grapes that are exposed to high humidity; the growth of the mold perforates the skin of the grape, opening a path for the water to leave. When wet weather is followed by dry, warm weather, the berries then dehydrate to reach the high sugar levels needed for late harvest. Two excellent examples of wines made under these circumstances are the Trockenbeerenauslese, or TBA, of Germany and the Sauternes wines of France.
[FIGURE 3-29 OMITTED]
The growth of botrytis is sometimes encouraged by artificial means, such as watering the grapes with overhead sprinklers, to get the needed humidity to start growth. In addition to the concentration of sugar, botrytis produce a number of compounds that affect the flavor of the wine. One of these, botrycine, has a distinctly apricot aroma. Thin-skinned grape varieties like Zinfandel will shrivel up in hot weather during the harvest season and significantly concentrate the sugar without the presence of mold. However, these late-harvest wines have a different, more "raisiny" character than botrytis-affected wines. Late-harvest grapes, because of their high solids and sugar, are notoriously difficult to press, and fermenting and clarifying the wine is no easier. The unique weather conditions that are required, combined with the difficulty of their production, make late-harvest wines both rare and expensive.
Late-harvest wines can also be made without the growth of Botrytis cinerea. In Germany and other cold-climate growing regions, the grapes can be left on the vine until freezing weather sets in at the end of the fall. Wines that are made from frozen grapes are called Eiswein, or ice wine. As the water in the berries freezes the remaining juice is concentrated, increasing the sugar level to about 35[degrees]Brix. The grape clusters are then picked, transported, and pressed while they are still frozen. The pressing is done very slowly and, as the juice is removed from the grapes, some of the water in the berries remains behind as ice. Like botrytized wines, the fermentation proceeds slowly and stops before it can complete, resulting in a sweet dessert wine.
Port wines are full-bodied red wines with about 10 percent sugar and 20 percent alcohol, and are native to the Douro River wine region in northern Portugal. Port-style wines are wines made in the style of Port, but produced outside the Port region. Historically, in the Douro River wine region, brandy was added to red wine to stabilize it for export. After a time, the practice of adding the brandy, or fortification, in the middle of fermentation was developed. This had the effect of killing the yeast while the must was still quite sweet. Because a deep-red wine with lots of tannins is desired for Port, and the time of the fermentation is limited, winemaking practices are designed to maximize extraction from the skins. There are a number of deep-colored red grape varieties grown in the Douro River region for Port production; some of the most popular are Touriga Nacional, Touriga Francesa, Tinta Cao, and Tinta Roriz.
The terrain of the Douro River is steep and rocky, conditions that stress the grapevines and help to intensify the character of the fruit. When the grapes are ripe, they are picked and brought to small wineries located near the vineyards called quintas. Traditionally, Port wines were fermented in a shallow stone trough called a lagar. The fruit was placed in the troughs and crushed by being trodden upon by cellar workers. The treading would continue, mixing the cap and juice throughout the fermentation, until the sugar had fallen to 12[degrees] to 14[degrees]Brix. At this point, the must would be pressed and brandy would be added at the ratio of one part brandy to three parts new wine in order to kill the yeast and preserve the residual sugar in the must. Although treading is still practiced at some wineries today, most Port is mixed during the fermentation by mechanical means.
After fermentation, the Port is transported down the river gorge to the city of Oporto on the coast. Here "Port houses" assemble the wines from many different vineyards and quintas into blends, based on their quality. Many of the Port houses have British names, which indicate their origins as export companies. Some quintas hold on to their product, bottling it under their name as a "single quinta" port. Port-style wines are made around the world and, like "champagne," "port" has become a generic term for the style of sweet red wine produced in the Port region of Portugal.
In California, sweet dessert wines are often made from the Zinfandel variety. Called "Zinfandel Port" the winemaking is a hybrid of the late-harvest and Port winemaking methods. The Zinfandel grape has thin skins and, when allowed to hang on the vine during warm fall weather, it can achieve sugar levels of about 30[degrees]Brix through dehydration. The grapes are then harvested and fermented on the skins and when the must reaches the desired sugar level it is pressed and the juice is fortified with alcohol to arrest the fermentation.
Sherry originated in Spain and, like Port, it is produced in a variety of styles. The Spanish have a saying that "there is a Sherry for every occasion." This reflects the wide range of sherries from light and dry table wines to the more common rich and sweet dessert wines. This is also an indication that Sherry was so important to the region that different styles have been designed to complement many types of food. The defining characteristic of Sherry is that it is purposely oxidized, making it high in acetaldehyde, which is the result of the reaction of ethanol (wine alcohol) and oxygen. This gives Sherry wines their distinctive roasted nut aroma. Wine drinkers who are not accustomed to Sherry can sometimes find this aroma unsettling because it is the same compound found in a table wine that has been spoiled by oxidation. Sherry was once one of the most popular wines in the United States, however, in recent years its consumption has declined significantly.
The flavor of Sherry is produced during the aging process so, like sparkling wines, a fairly neutral wine is desired as a base for Sherry. For this reason, neutral grape varieties like Palomino are used for its production. Sherry production starts by fermenting the base wine to dryness and fortifying to achieve an alcohol content of about 15.5 percent. The high alcohol level inhibits the growth of vinegar bacteria. To reach this level, the grapes must be very sweet and sometimes they are dried on mats after picking to reach the appropriate sugar concentration. After the base wines are made, they are graded by color, taste, and body to determine which type of Sherry they will be used to make. The lighter wines are inoculated with flor yeast and called fino or manzanilla (when aged in the coastal region of Sanlucar de Barrameda, Spain). The more full-bodied wines are fortified with brandy to 18 to 20 percent alcohol and called oloroso. The wines are then placed in partially full barrels to expose the wine to oxygen.
In the fino Sherries, the flor yeast begins to grow, using the alcohol that is present as an energy source. As it grows it forms a thick film on the surface of the aging wine because it can grow only in the presence of oxygen. Sherries made in this style are light and dry and are an excellent table wine to accompany savory foods. In the United States, however, the more popular style Sherry is the full-bodied oloroso. After the oloroso is fortified, it is aged in partially full barrels but without flor yeast. Oloroso Sherries are often sweetened before bottling to make a dessert wine.
The traditional method of aging Sherry is also unique; it is done in a fractional barrel system called a solera. The barrels of a solera are set up in five to twelve tiers. When it is time to bottle, one-quarter of the wine on the bottom level is removed for bottling. It is replaced by one-quarter of the wine from the next highest tier. This process goes on until one-quarter of the wine from the top tier is moved to the next level to make room for the wine from the new vintage. Solera aging provides a great deal of consistency from year to year, and as a solera system matures, the average age of the wine that is bottled gets older. There is another saying in Spain: "No one sets up a solera for themselves, they do it for their grandchildren."
In California, methods of production differ significantly from those in Spain. Flor yeast is often grown in a submerged culture made possible by bubbling oxygen through the tank until it has reached the desired flavor. California sherry is often finished by aging in barrels at an elevated temperature, more similar to the production of Madeira than Spanish Sherry.
The Attributes of Wine
Wine is a complex mixture of nearly 1,000 different, naturally occurring chemical compounds. These constituents come from three sources: (1) the compounds that are present in grape juice, (2) the compounds that are produced by microorganisms fermenting the grape juice, and (3) the compounds that are added by the processing and aging of the wine. In addition to the natural chemicals in wine there can also be a small amount of man-made materials that are added to wine, usually in the form of sulfites used as a preservative (Figure 3-30).
The major component of wine is water, making up 80 to 90 percent of the solution. Water content affects the chemical and sensory qualities of wine, but its most important role is as the solvent in which all other wine constituents are dissolved. After water, alcohol, or more specifically ethyl-alcohol, or ethanol, is the next most prevalent compound. It has a significant role in the sensory and stability aspects of wine, as well as many physiological effects. Glycerol is another type of alcohol that is produced by yeast. Unlike ethanol, it is nonintoxicating but it does make sensory contributions to the viscosity, or body, of the wine. Organic acids are present in about the same quantity as glycerol but have much more of a sensory effect. A wine's natural tartness is one of the qualities that make it an excellent accompaniment to food. The acids in wine also contribute to its microbial stability by inhibiting the growth of bacteria.
Some of the most important flavor compounds in wine are present in very small amounts. Trace constituents such as phenols, esters, and sugars each represent groups of complex chemical compounds with similar structures. Each of these groups has many members; for example, there are ten different alcohols found in wine besides ethanol and glycerol. Each individual wine has a unique combination of these chemicals that gives it a distinctive character. The various amounts of these compounds present are determined by factors such as grape variety, the vineyard's terroir (total environment, including soil, climate and location), and the production decisions that the winemaker and the grower make.
A wine's sensory qualities are determined by its chemical makeup, and the chemical makeup of a wine is influenced by a vineyard's terroir and the actions of the grape grower and the winemaker. As described in the previous chapter, the grower sets the stage for a wine's flavor by controlling factors such as selection of a clone and how the vineyard is pruned. Once the fruit is delivered to the winery, the winemaker takes over. Winemaking decisions including when to press, and what type of barrels to age in, build upon the flavors that the grape grower established in the vineyard. The great complexity of a wine is ultimately shaped by numerous choices available to the people who produce it. This is why there are so many different types of wines made around the world and also why they are made in such a variety of styles. The interpretation of what a Cabernet Sauvignon should taste like varies from region to region, winery to winery, and vintage to vintage. In the end, the consumer of the wine makes the ultimate decision on which interpretation is the proper one.
After reading this chapter, you should be able to
* display an understanding of how both red and white table wines are produced.
* describe how sparkling wine is produced.
* explain how dessert wines are produced.
degrees Brix ([degrees]Brix)
1. Discuss the three major products of alcoholic fermentation and explain their significance in the winemaking process.
2. What is the defining sensory characteristic of sherry wines? Explain how that characteristic is produced.
3. What is the difference in the pressing of red and white wines?
4. What is the definition of a table wine?
5. How does aging a wine in oak barrels affect its flavor?
6. Describe the various methods of sparkling wine production.
7. What effects does malolactic fermentation have on wine?
8. What processes does a wine undergo to be finished for bottling?
Carbonic Maceration and Extended Maceration
In red wine production, the most important stylistic decision a winemaker has to make is the manner in which the skins are handled during fermentation. How this is done will determine most of the flavor components in the finished wine. There are many ways to influence extraction from the skins beyond how the cap is punched down or pumped over. Two of the most common procedures are carbonic maceration and extended maceration.
Carbonic maceration is the process whereby either a portion or all of the grapes are not crushed but loaded into the tank as whole clusters. The weight of the fruit crushes some of the berries at the bottom of the tank and releases juice. A small amount of fermenting must is added to begin fermentation and to fill the tank with carbon dioxide. As the fermentation in the juice progresses, it also begins to take place within the cells of the intact grape berries. This intercellular fermentation produces soft tannins and a unique strawberry or bubble-gum aroma. This technique works well with both Pinot Noir and Gamay and is the trademark characteristic of Beaujolais Nouveau.
Another method of production, extended maceration, is more suited to big-bodied red wines such as Cabernet Sauvignon. With this technique the fruit is crushed and fermented with typical cap management; at the end of fermentation, however, the must is not pressed. Instead, the tank is topped off and the skins are left in contact with the young wine for 1 to 8 weeks. At first, the young wine becomes more bitter and astringent from the increased skin contact, but after several weeks, the tannins begin to polymerize. This is the process whereby small, harsh tannins join together and become so large that they are no longer soluble and begin to drop out, leaving the finished wine softer and more drinkable.
In addition to being very sweet, grape juice is also quite tart. This natural acidity primarily comes from the presence of two types of acid: tartaric and malic. Malic acid is found in many fruits, while tartaric acid is unique to grapes (Yair, 1997). There is a group of microorganisms, called malolactic bacteria, that can use malic acid as an energy source for growth. They do this by converting malic acid in wine or grape juice into lactic acid, the type of acid found in milk (Figure 3-17). Malolactic fermentation usually takes place after the primary fermentation, or alcoholic fermentation, and occurs at a much slower pace. Often the fermentation takes place in barrels, sometimes not completing until the spring following the harvest.
Malolactic fermentation has several effects on the wine, the primary effect being deacidification. Since malic acid is stronger than lactic acid, a wine will taste less tart and have a higher pH (lower acidity) after fermentation. Malolactic fermentation also makes wine more microbiologically stable. If malolactic fermentation finishes during aging, it will not be able to spoil the wine by taking place after the wine is bottled and the wine will not have to be filtered as tightly as a nonmalolactic wine.
[FIGURE 3-17 OMITTED]
Finally, malolactic fermentation produces a compound called diacetyl that has a distinct buttery character. The presence of diacetyl is more noticeable in white wines than reds; Chardonnays often go through malolactic fermentation to get this aroma. Winemakers can encourage malolactic fermentation by adding cultures of the bacteria after primary fermentation or by placing the wine into barrels that have previously been used for wines undergoing malolactic fermentation. Malolactic fermentation is usually encouraged in red wines for reasons of stability, and because it is difficult to prevent it from spontaneously occurring during the long barrel-aging process. With white wines, it is a stylistic concern; in a light-bodied, fruity wine like Riesling, it is usually avoided, while in a rich, oak-aged Chardonnay it would be more appropriate.
Table 3-1 Types of Port TYPE WINEMAKING METHOD WINE STYLE Ruby Blended from several Bright ruby-red in color vintages and aged from with a fruity aroma. Meant 2 to 3 years in oak casks to be consumed soon after before bottling. bottling. Vintage The highest quality Port, Deep red color and more blended from lots all complex flavors and produced in the same aroma then Ruby Port. It harvest; only the best should be aged for 10 to years are selected to be 30 years in the bottle "vintage." Aged from 1 to before consumption. Due to 2 years in casks, it is long bottle aging, there is then bottled without usually a great deal of filtration. sediment in the bottle. Late Bottled Ruby Ports blended from a Good quality wine that does Vintage single non-vintage year, not have the intense aged in casks for 4 to 6 flavors found in vintage years before bottling. Port. Meant to be consumed soon after bottling. Vintage Ruby Ports blended from Good quality wine that does Character several vintages and aged not have the intense 4 to 5 years in oak casks flavors found in vintage before bottling. Port. Meant to be consumed soon after bottling. Tawny Port wine that has been Extended aging gives them aged 10 to 40 years in amber, "tawny" color casks before bottling. and a slightly oxidized character. Meant to be consumed soon after bottling. White Port wine made from white Light gold in color, it is grapes, usually has made in a variety of styles limited aging in casks. from dry to sweet. "Zinfandel Late-harvest Zinfandel Lighter in color than Port" grapes are fermented then traditional Port, fortified to arrest the dehydration fermentation before aging on the vine gives it a and bottling. distinctive "jammy" aroma. Table 3-2 Types of Sherry TYPE WINEMAKING METHOD WINE STYLE Fino Aged in partially full Pale yellow in color with a (Manzanilla) barrels under a surface distinctive nutty aroma. layer of flor yeast Dry and served slightly growth. chilled. Alcohol 15.5 to 18% Amontillado A mature fino Sherry Darker than fino Sherries with that is allowed to a richer flavor and oxidize as it ages nutty aroma, dry with alcohol in partially filled from 16 to 22% barrels after the flor yeast is removed. Oloroso Fortified before aging Dark amber in color and dry to to prevent flor yeast slightly sweet (1 to 3% growth, aged in sugar), alcohol from 17 to 22% partially filled barrels. Cream Sherry Fortified before aging Dark amber in color and sweet to prevent flor yeast (7 to 10% sugar), alcohol from growth, aged in 17 to 22% partially filled barrels. Sweetened before bottling. Baked Flor yeast is grown Dark amber in color and (California throughout the wine usually sweet (7 to 10% Style) (submerged culture) by sugar), alcohol from 17 to 22% bubbling oxygen through the tank. After fermentation the wine is heated to 130[degrees]F (55[degrees]C) for 1 to 3 months. FIGURE 3-30 Table wine composition. Table Wine Composition Water 80 to 85% Alcohols 10 to 15% Acids 0.5 to 1% Sugars 0.1 to 3% Mineral Salts 0.2 to 0.4% Aromatic Compounds 0.01 to 0.1% Phenolic Compounds 0.01 to 0.5% Sulfur Dioxide .0025 to 0.01% Note: Table made from pie chart.
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|Title Annotation:||SECTION I: The Basics|
|Author:||Henderson, J. Patrick; Rex, Dellie|
|Date:||Jan 1, 2007|
|Previous Article:||Chapter 2: The vineyard--from soil to harvest.|
|Next Article:||Chapter 4: Tasting wines.|