Wine Academy

Winemaking

Wine is not all one thing. Winemaking processes different from grape to grape, from region to region, from high-end to low-end, certainly from style to style. To break down this complicated subject at least a little bit, we will cover winemaking by dividing it into five general areas:

  • Red wines
  • White wines
  • Rosé wines
  • Sparkling wines
  • Fortified wines
a. Red Wine Making

The process of making red wine begins with the harvest. Since the skins of red wine grapes contribute to the wine’s color and flavor, the careful harvester tries to keep the bunches of grape whole. Individual plastic boxes are used to avoid a situation in which grape skins will break from the weight of grapes above (if the grapes were, for example, shoveled into a large hopper). The careful winemaker will put together a sorting line, so that quality grapes can be separated from shriveled or diseased grapes and also to avoid getting any matter other than grapes (MOG) into the fermentation vessel. The grapes may then be sent through a de-stemming machine or be de-stemmed by hand. Some red winemakers choose not to de-stem, and send the stems into the fermentation vessel with the grapes. The stems can add tannins.

The next step is to crush the grapes. This was traditionally done with an implement that seemed perfectly designed for crushing grapes without crushing the seeds inside: the human foot. Crushed seeds can add bitterness to the mix. Modern crushing machines now use rollers or paddles to do the same thing. Some are combination crusher-de-stemmers.

The crushed grapes and the juice they exude next go into a fermentation vessel. The winemaker at this point will either add commercial yeast or depend on local ambient yeast

to begin the fermentation process. During fermentation, yeast converts the grape sugars into alcohol. This alcohol acts on the skins of the grapes to extract anthocyanin pigments, flavor elements, and phenolic compounds, particularly tannins. The seeds also contribute tannins. This alcoholic extraction is generally not enough to produce a deep colored red wine, however. The wine requires an additional soaking, or maceration period, to bring out all its potential color and flavor. A low-end, mass-produced red wine might see a fermentation period of only several days. A big red wine designed to age might undergo a fermentation of a week followed by an extended maceration of several weeks. In order to extract color, red wine is usually fermented at a higher temperature than white wine. In addition, exposure to oxygen is more prevalent in red wine making than in white. This is because phenolic compounds in red grape skins, stems and seeds slowly react with the oxygen to form pigmented tannins, which contribute positively to the red wine’s eventual texture.

The crushed skins, seeds and stems, if any, in red wine fermentation tend to float to the top of the fermentation vessel and form a “cap” that tends to prevent contact between the skins and the juice. Two methods come into play to integrate the cap materials with the juice in order to assure maximum extraction. In punching down (pigeage in French), a winery worker will use a spade-like tool to break the cap and push it down to the bottom of the fermenter, allowing the juice to rise to the top. This procedure, still done primarily by hand, must be done several times a day over the fermentation and maceration period. In pumping over, a hose is placed deep into the fermenter to allow wine from the bottom of the fermenter to be pumped over and onto the top of the cap, thus breaking the cap and circulating its contents among the wine. This is often accomplished using automatic devices.

 

After the wine goes through its alcoholic fermentation it might undergo an additional pressing operation. The free-run wine from the initial crushing is collected in a tank. The skins and seeds that remain are then sent through a wine press, creating what is known as press wine. The free run wine is often of a better quality than the press wine. Since the majority of the grape’s acidity is lodged in the grape pulp, free run juice is more acidic, press wine more tannic (the tannins come from the skins). The two types of wine may be processed into separate batches of wine, or they might be combined. With a traditional basket press, the winemaker turns a large screw device that serves to press the grapes so that the press wine runs out at the bottom. Modern wine presses, which are often computer controlled, can exert a specified amount of pressure on the grapes, and have the ability to generate multiple press runs of different pressure levels. This is a way to arrive at just the right level of tannin in the press wine so that the combined wine has the balance of tannin and acidity the winemaker is looking for. At this point (or further down the line during the barrel aging process), the red wine might be racked: pumped from one container to another so that sediment may be removed in successive stages.

Most red wine undergoes a process of malolactic fermentation at some point after the primary fermentation is completed. In “malo,” lactic acid bacteria (which may already be present in the wine or may be added) metabolize harsh tasting malic acid in the wine and replace it with softer lactic acid. This operation must be carefully monitored because it tends to reduce the total acidity in the wine. Acidity, especially in warm climate regions, is a precious commodity.

Not all red wine sees contact with oak, but in general red wine is matured in oak barrels or casks much more frequently than is white. In barrel maturation, substance like phenolic tannins already in the wine combine with phenolic compounds from the wood for additional level of flavors. As with any process in winemaking, oak contact must be accomplished with skill and some restraint. Serious red wines age eighteen months or longer. The winemaker must choose between new oak, oak used one or more times, and among types of oak (French or American, for example) before determining the final blend. The size of the barrel also makes as a difference—the smaller the barrel, the greater the oak contact. In less expensive wines, oak chips, staves, and even oak juice are often used to add oak elements more quickly. In some parts of Europe, woods other than oak, like acacia or chestnut, are sometimes used.

Before blending and final bottling, wines may go through a process called fining. The winemaker adds a fining agent to the wine that attracts and clumps up fine particles, yeast cells (alive and dead), and tannins the winemaker wishes to remove from the wine. The now-heavier particles sink to the bottom where they can be racked out. Many fining agents are based on animal products: blood and bone marrow, casein (milk protein), chitin (fiber from crustacean shells), egg albumen (derived from egg whites), fish oil, gelatin (protein from boiling animal parts), isinglass (gelatin from fish bladder membranes), diatomaceous earth (remains of ancient sea creatures). To make a wine vegan, non-animal alternatives are bentonite clay, kaolin clay, plant casein, silica gel, vegetable plaques, and limestone (although as to the last, it seems to this writer than a strict vegan would take limestone off the list, since, although it is a rock, it is derived from the remains of ancient sea creatures).

Nearly all wines get doses of sulfur dioxide to act as an anti-microbial agent and antioxidant to prevent spoilage. Filtering, which is controversial because many believed it detracts from flavor and liveliness in a wine, can remove some microbes, but only preservatives like sulfites can keep the microorganisms down over the long term. The alternative, in a sulfite free wine, is the keep the wine refrigerated at all times from bottling to consumption (and, even so, it should not be kept for long before enjoying). For a wine to keep long term, it needs chemical protection.

In fine wines, the various phenolic and other compounds continue to interact and gain layers of sophistication when aged in their bottles. At least this is the potential, but so much depends on how the wine is shipped and stored, and the intangibles of organic chemistry.

b. White Wine Making

The term “white” loosely describes wines that range from nearly without color to ranges of straw, yellow, and gold.

Color in wine comes largely from contact between the grape juice and the grape skin. Hence, it is possible to make a white wine from the juice of a red grape if the winemaker prevents or minimizes skin contact. We will look into this phenomenon in the coming sections on rosé wines and sparkling wines, but for now, when we speak of white wines we mean white wines made from white grapes.

You cannot make a red wine from a white grape, but you can make a deeply colored “orange” wine from white grapes if you macerate the juice on the skins for a long period to extract whatever pigments are available in the skins of the light-colored grapes. When we speak of white wines we mean white wines made without this kind of maceration.

It is useful to highlight some of the general differences between the process that produces white wine and the process used to produce red wine that we have just covered.

  • White wine usually ferments at cooler temperatures than red wine.
  • We ferment white wine almost always in closed fermentation vessels while we may use open vessels for red wine.
  • White wine is less likely to see oak aging that red wine, and if it is aged in oak, the aging is for a shorter period and with less aggressive oak.
  • Nearly all red wines undergo malolactic fermentation to soften their acidity, but this is only done with some white wines.
  • Most crucially, we press white wines to separate the juice and the grape solids before alcoholic fermentation but press red wines after alcoholic fermentation.

We begin in the vineyard. As with red wine, our goal is not to damage the grapes, so we use stackable plastic boxes to protect the grapes from being crushed by their own weight. It is also important to keep the grapes as cool as possible through the entire winemaking process, and so we might harvest at night under lights (which increases operational costs).

Next, as with red wine, we sort, de-stem, and crush the grapes. Unlike the red wine process, we then press the sweet pomace that remains to separate the juice from the solids. We want to avoid further contact between these solids and the juice to prevent phenolic compounds (so essential to the red wine process) from promoting oxidation in the more delicate white wine or adding unwanted astringency, unwanted amber or brown coloring, and other effects. Oxidation, which is widely tolerated by red wines, causes acetaldehydes to be produced which can compromise the aromas of the white wine. At this stage, also to prevent oxidation, we add sulfur dioxide (sulfites). Because white wines lack the antioxidants found in red wines (tannins, proteins, phenolic compounds), they generally require a higher level of sulfur dioxide than do red wines.

Some optional steps at this point involve:

  • Chilling the juice
  • Allowing the sediment to settle out of the juice
  • Racking
  • Clarification. In this step, the wine is bulk chilled in stainless steel to precipitate out tartrate crystals, which, though harmless, give the appearance of shards of glass when the wine is bottled.

Next comes the alcoholic fermentation process using ambient or cultured yeast. Most white wines are fermented in closed stainless steel vessels, often mechanically chilled, but an option, often chosen for high-end Chardonnay (the most popular of the white wine grapes) is to ferment in an oak barrel to add texture body and mouthfeel. It is important to distinguish barrel fermentation from barrel aging (a wine could be subject to both). Wines fermented in oak have less oak influence than wines aged in oak, with better integrated oak flavors and well-defined fruit. Since the juice is totally separated from the solids, the cap so prevalent in red winemaking does not exist, and so there is no need to punch down or pump over during fermentation (and there is no maceration step in the first place).

The next option is malolactic fermentation. In “malo,” lactic acid bacteria (which may already be present in the wine or may be added) metabolize harsh tasting malic acid in the wine and replace it with softer lactic acid. It is this process that creates the buttery taste evident in some Chardonnays.

The white wine may now be aged in oak barrels or casks, but the vast proportion of white wines see no oak. In some wines, oak flavors and aromas are accomplished by macerating oak chips or staves, or by adding liquid oak extract.

A further option now is lees aging, with or without lees stirring. Fermentation creates enzymes which break down yeast cells in a process called autolysis. Cells release flavor and texture compounds such as mannoproteins, amino acids, esters, aldehydes, ketones, and others. These compounds add creaminess, richness and body to white wines. Lees aging may go on for more than a year in some cases. Obviously, this step adds to the cost of the wine.

Because of color issues, the fining process, in which a fining agent attracts yeast cells (alive or dead) and other particles so that they can clump up and sink to the bottom of the tank, is important in white wine production. Subsequent filtration to remove bacterial and superfine particles is another option. The white wine is ready to be bottled, and sometimes aged in bottle.

Rosé Winemaking

As we have already discussed, you can make a white wine from red grapes by preventing any contact between the grape skins and the juice, since the color comes from the skins. If you allow some skin contact by briefly macerating the red grape skins in the juice (say, 24 hours), you arrive at a lightly colored, pinkish wine. The term “blush” wine applies to some very pale colored wines. Some lightly colored wines made by slight skin contact are termed “white” wines as in “white Zinfandel.” Another method is the saignée process, a component in red winemaking (saignée means bleed). The winemaker bleeds off some of the lightly colored juice so the skins, seeds, and stems that remain contribute to a more concentrated color, flavor and tannins in the remaining red wine. Rather than waste the runoff, the winemaker produces it as a rosé. In the vin gris (gray wine) process, the wine is made from certain red grapes. The solids and the juice are immediately separated after pressing without any maceration. The wine is not actually gray but a very pale pink. French law requires that this method use lightly tinted red grapes like Gamay (the grape of Beaujolais). Another way to produce a pink wine is to subject the wine to a de-colorization process using activated carbon. This process is avoided by fine wine makers since flavors and aromas tend to also be stripped along with the color. The actual blending of finished white and red wines is not permitted in France, but there is an exception: pink Champagne may be produced by blending.

In its broadest sense, the term “sparkling wine” indicates any wine in which bubbles rise to the surface after opening. Beyond this general definition, the category is broad. We can categorize these wines by country of origin, by base-grapes used, and certainly by method of production.

 The European Union defines a wine as “sparkling” if it contains at least three atmospheres of pressure. Wines fitting in this category include French Champagne (usually six atmospheres), mousseux and crémant (also French), spumante (Italian for fully sparking), sekt (German). Semi-sparkling covers 1 to 2.5 atmospheres, using terms such as frizzante, pearl, pétillant and spritzig.

 In fermentation of grape juice, we say for convenience that the yeast metabolizes the grape sugar and creates alcohol, but in actuality the process also generates carbon dioxide. In still winemaking, we vent off the carbon dioxide (taking care that it does not collect in pockets around the winery where the odorless gas has the potential to quickly kill winery workers). In sparkling winemaking, we use a number of methods to carbonate the wine. We may generate the carbon dioxide in a sealed bottle, in a large sealed tank, or we may simply inject it into the wine.

Sparkling Winemaking

 

In its broadest sense, the term “sparkling wine” indicates any wine in which bubbles rise to the surface after opening. Beyond this general definition, the category is broad. We can categorize these wines by country of origin, by base-grapes used, and certainly by method of production.

 

The European Union defines a wine as “sparkling” if it contains at least three atmospheres of pressure. Wines fitting in this category include French Champagne (usually six atmospheres), mousseux and crémant (also French), spumante (Italian for fully sparking), sekt (German). Semi-sparkling covers 1 to 2.5 atmospheres, using terms such as frizzante, pearl, pétillant and spritzig.

 

In fermentation of grape juice, we say for convenience that the yeast metabolizes the grape sugar and creates alcohol, but in actuality the process also generates carbon dioxide. In still winemaking, we vent off the carbon dioxide (taking care that it does not collect in pockets around the winery where the odorless gas has the potential to quickly kill winery workers). In sparkling winemaking, we use a number of methods to carbonate the wine. We may generate the carbon dioxide in a sealed bottle, in a large sealed tank, or we may simply inject it into the wine.

 

The traditional method of sparkling wine production used to be called the méthode champenoise, but the French have put a lid on this term in their ongoing effort to assure that the term Champagne and any variation thereof applies only to wines produced in the region of Champaign in northeast France. No other EU country may use the term Champagne or méthode champenoise. Some American winemakers still use the term, but this disallows their wines from being sold legally in the EU. The best American sparkling wine producers, a number of which are owned by French Champagne houses, label their top of the line products “Traditional Method sparkling wine.” Of course, no one can legally limit the “look” of the standard dark green Champagne bottle with its gold-foil covered neck. The traditional method is used for Champagne in Champagne, for high end sparkling wines in other regions of France (where the term used for the wine is often crémant), and for sparkling wines elsewhere. In the northern Italian region of Piemonte, you can find traditional method gems that are rarely known outside the region.

 

 

Caption: “A California sparkling wine labeled Champagne and showing the complete look of a Champagne bottle. The French do not like this.”

In the traditional method, the grape juice first ferments into a still wine that is specifically constituted to undergo further steps. This wine will be sharp and highly acidic, and not very appetizing to drink. The different Champagne houses take great pains to blend these base wines so that they consistently reflect the “house” styles. The wine then undergoes a second fermentation in the bottle. The winemaker adds yeast and a tirage of sugar into each bottle, seals the bottle with a crown cap, and patiently waits for the second fermentation to occur, on a bottle by bottle basis. You might be starting to think here that the final result will be expensive, and you would be right. This second fermentation in a sealed environment creates the bubbles as the carbon dioxide is trapped and forced to integrate with the wine. It also creates sediment, called lees, which must eventually be removed.  To accomplish this, the bottles are stored necks slanting down in racks so that gravity will coax the lees down to the neck area. The bottles will then be put through remuage (riddling) in which each day the individual bottles are turned and adjusted slightly so the lees slide gradually into the neck without roiling the delicate wine. Experts used to do this laborious task by hand, but many wineries today have large machines called gyropalettes for this task. Non-vintage Champagne must be stored this way on the lees for a minimum of fifteen months, vintage Champagne at least three years.

Once the in-bottle fermentation and lees storage is complete and the sediment is safely ensconced in the necks of the individual downward-facing wine bottles, the wine must be disgorged. The winemaker chills the necks of the bottles so they freeze into a chunk of ice, turns the bottle upright, flips off the crown cap and watches the pressure in the now carbonated wine push out the precipitate. There is now a quantity of wine missing. The winemaker will fill each bottle with still wine and also add a precise amount of sugar, the dosage. The wine added is called the liqeur d’expedition. The level of sugar added will affect the sweetness level of the final wine. The wine is bottled for the last time with a special cork and a protective wire cage.

Caption: “Gyropalettes allow Champagne producers to pass the savings in labor costs on to you, the consumer (but they do not – they keep the money).”

The ancestral method is older than the traditional method. It may also be called the méthode rurale, or méthode artisanale. Here the wine undergoes a first alcoholic fermentation and then is bottled before the fermentation is complete, continuing to ferment in the bottle and creating carbon dioxide bubbles one the bottle is sealed. There is neither disgorging nor dosage, hence the final wines may be cloudy in appearance. It takes a great deal of skill to produce sparkling wines using this ancestral method. The wines tend to be rural and somewhat obscure.

The transfer method is something of a hybrid between methods. The wine undergoes its first fermentation, is bottled to accomplish the second fermentation, and then bottles are emptied into a tank, giving the maker a chance to adjust the blend. This method reduces the chance of bottle variation inherent in the traditional method. The wine is rebottled, with a dosage added. This method is used often for sparkling wines that eventually go into unusually small or unusually large bottles, and is popular in Australia and New Zealand.

The charmat method, of Italian invention, is also called the tank method or Martinotti method. It is used in Asti and Prosecco wines to give a much lighter effervescence than Champagne, and to preserve delicate fruit flavors. The wine is fermented in a stainless steel pressure tank. Once the juice ferments properly, the wine is filtered to remove the yeast, and then it is bottled. The longer the fermentation time, the more delicate the bubbles and aromatic qualities.

Caption: “The less expensive, less fussy Prosecco is successfully competing against Champagne in the sparkling wine market.”

The soda method is an industrial process that injects carbonation into still wines. Bubbles here are large and lack the delicate beading of sparkling wines produced using any of the above methods. These wines quickly go flat.

Fortified Wines

A fortified wine is a wine to which brandy or some other type of sprit is added at some point in the production process. The result is a wine that is higher in alcohol than a standard still wine. Depending on production process and wine style, the fortified wine might or might not be also sweet. Port, Sherry, Madeira and Marsala are the best known fortified wines. Fortification of wine originally started as a means to preserve wine over long sea voyages. Consumers eventually came to appreciate the subtleties of flavor and texture created in these wines (often by the sea voyage itself), and industries developed to produce them for the public, often under British leadership.

Although widely imitated around the world, true Port can only be produced in the Oporto region of Portugal from grapes that grow on difficult terraced slopes in the Douro valley in Portugal’s north. The wine is fermented but prior to complete fermentation the producer adds a neutral grape spirit called aguardiente to stop the fermentation before all the sugar has been metabolized by the yeast into alcohol. This leaves sweetness in the wine and also adds alcohol to a total of about 20%. Contrast Spanish Sherry where spirit is added only after the wine has completely ferment to dryness. Any sweetness in Sherry comes from the addition of sweetener later on. Hence Port is always sweet, but Sherry may or may not be sweet.

Caption: “Rabelos, a type of boat traditionally used to transport barrels of port down the River Douro for storage and aging in caves at Vila Nova de Gaia near Porto. Photo by Thomas Istvan Seibel.”

Tawny Ports are aged in wooden barrels that allow oxidation to promote gradual evaporation. The wine turns golden brown during this process and takes on a nutty character. The official age categories, as stated on the label, are 10, 20, 30 and over 40 years. Aging in bottle is irrelevant.

A Colheita Port is a single vintage aged in tawny style for at least seven years. This wine shows the actual vintage on the label instead of the usual Tawny Port indication of age. Even though Colheita Port shows the vintage on the label, it is not Vintage Port, which ages primarily in the bottle.

Ruby Port is the inexpensive, mass-produced variety. It is not aged.

Vintage Port is the wine all the fuss is about. Only every few years, perhaps three times a decade, individual port producers (called shippers) feel their base wines are good enough to declare a vintage. A vintage port will go through its first aging process in barrels or stainless steel for a maximum of two and a half years. Because of this short aging period, the Vintage Port retains its deep ruby color and deep fruit flavors. The important aging process goes on in the bottle and is often measured in decades, or even centuries. Because bottle aging develops a crusty sediment, Vintage Port must often be decanted before serving. A Single Quinta Vintage Port is a wine whose grapes have been sourced on an individual estate, or quinta.

Late Bottled Vintage (LBV) Port is a relatively new Port product, created from wine originally slated for vintage production, but one that did not succeed in reaching vintage Port status      due to lack of consumer demand or other reasons. The LBV will go through a longer barrel or container aging period than standard vintage port, perhaps four to six years. The wine may be filtered before bottling, which removes the sediment and obviates the need to decant the wine before serving. Typically, LBV Ports will not improve with age in the bottle.

Sherry

The first thing you need to know about Sherry is that it has an image problem. While certainly makers outside of Sherry’s original home in southern Spain can and do produce credible Sherry-like wines, others have been responsible for spewing out highly sweetened, poor quality wines labeled Sherry. The sweetness here often serves the purpose, as it does so often in corner-cutting wines, of masking winemaking defects.

Real Sherry-from Spain is not always sweet. The types called Fino, Manzanilla, Amontillado,

Palo Cortado and Oloroso are most commonly completely dry, with a maximum of 5 grams of sugar per liter. Sherry labeled “dry,” however may be much sweeter, as well as Sherry labeled “medium” and “cream.”

Because of that image problem, many wine commentators consider good Sherries some of the best values on the wine market today.

The name Sherry derives from the Spanish town of Jerez de la Frontera in the province of Cadiz, part of the Andalusia region on the southern coast. Most Sherry is produced from the Palomino grape, although some sweet dessert Sherries have components of Moscatel and Pedro Ximenez grapes.

Let us take a moment to distinguish Sherry from that other Iberian fortified wine, Port. Port is fortified with spirits before fermentation is complete, leaving unfermented grape sugars in the wine, so Port is always sweet. Sherry is fortified after the grape sugars have been fermented to dryness. Sweetness in Sherry, if any, is added in a subsequent step, so some Sherries are sweet.

Also unlike Port, Sherries do not generally have specific vintage years. This is because Sherry is aged in what is known as a fractional solera system. The finished Sherry ends up a mixture of ages, the average age increasing the solera, a collection of stacked barrels, gets older. Solera means "on the ground" in Spanish, literally the lowest level of barrels. Sherry is bottled from these oldest barrels, the second level is used to refill the lowest level, the third level the second level, and so on. Newly fermented wine is put in the highest level. The barrels are not always actually stacked in the Sherry aging house, which can be immense; someone just keeps careful track of which is which.

Caption: “A Sherry aging Solera.”

Fino Sherry is the palest and driest. When Fino ages, a covering of a yeast called flor (which is derived from the local environment) develops, preventing contact with the air. A variety of Fino that ages in the sea air of the town of Sanlúcar de Barramedia is called Manzanilla.

Amontillado is initially aged under flor but is then exposed to oxygen, producing a darker sherry than Fino but one still lighter than Oloroso.

Oloroso is aged with oxygen contact longer than Fino or Amontillado, producing a dark, rich wine with alcohol as high as 20%., as opposed to 15-17% for the others.

Amontillados and Olorosos are naturally dry. Sometimes they are sweetened, but if so they must be labeled using a variation of the term Cream Sherry, which always connotes sweetness, and the term Amontillado or Oloroso may not be used.

Palo Cortado starts out as an apparent Fino, but then either the flor dies on its own or is killed by filtration. The result is more like an Oloroso than a Fino or Amontillado.

Jerez Dulce (sweet Sherry) is made either by fermenting dried Moscatel and/or Pedro Ximenez grapes or by starting with a dry Sherry and adding sweet unfermented grape must. The wine is syrupy thick and nearly black.

Cream Sherry is a sweet blend of several sherries, commonly Oloroso and Pedro Ximenez.