Grow Grapes...
Pick Grapes...
Crush Grapes...
Ferment Grapes...
Bottle Wine
While the art of winemaking isn’t nearly this easy, there are a few basic steps that must be followed in the overall process. While each step plays a very important role in and of itself, all that is really needed to turn grape juice into wine is the simple, entirely natural process of fermentation. Fermentation is the chemical change of sugar into alcohol and carbon dioxide gas brought about by yeasts which live on grape skins or are added in the process. For purposes of this lesson, we will skip the technical aspects of growing and picking grapes and go right to the crush, which is as much a science as it is a social experience.
Crushing
After all grapes have been harvested, the first stage in winemaking is extracting the juice. The most common method for obtaining juice from grapes is known as crushing. Pressing is a second method, while the third is the old-fashioned way practiced in remote parts of the wine world, treading or stomping grapes. When ripe, grapes are plump and their skins so soft that they can be broken easily. Both grapes and juice are vulnerable to deterioration, so winemakers are careful to avoid any delays. The juice must be extracted without breaking the bitter seeds (called pips) and the stems must be removed as they contribute to bitterness in wines as well.
In California, the juice is usually obtained through a high-capacity crushing and pressing operation for speed, and generally employs at least two sets of crushers for making red and white wines. This avoids color problems in the white wines. The grape juice is separated from the leaves, stems and seeds in a continuous process through a series of paddles and/or rollers in a perforated, rotating drum. An average size winery can process about 40 tons of grapes per hour and larger wineries can handle upwards of 150 tons per hour. A ton of grapes yields somewhere between 60 to 70 cases of wine.
While a majority of all wines begin with crushing, there are exceptions. Occasionally, a winemaker decides that crushing is not the best method of extracting the juice for a particular wine. In the process of crushing, the juice spends time in contact with the grape skins, which can contribute to both color and possibly some degree of bitter flavor. High heat while in contact can bring out the negative aspects. So the main reason to avoid crushing is to minimize color and bitter components in the juice as these can show up in the finished wine. By the way, many white wines are actually produced from red grapes as a result of little if any contact with the grape skins. “Blush” wines are made with minimal skin contact.
Pressing
The basic mechanics of pressing involve forcing the just-harvested grapes against an immovable object to extract juice through pressure. The pressure applied can be regulated so that the amount of juice extracted is also controllable. The more pressure applied, the more juice extracted, but the juice quality may decline.
Sometimes the grapes are so fat and thick-skinned; it takes a little external effort to start the juice flowing. When grapes are piled high, the weight of the grapes alone may be sufficient to break the skins. The juice that flows easily with little or no external pressure is known as free-run juice. As the amount of pressure used in a winepress increase, so does the likelihood that the juice will contain unwanted flavor compounds. Under extreme pressure, grape skins can be so severely pressed that they shred and release harsh, bitter flavors; but with light or only medium pressure, unwanted compounds can be wholly or at least partially avoided. The juice from heavy pressure may be used as some percentage of the blend or not at all.
There are all types of winepresses and all have evolved considerably from the often-depicted wooden press with slotted basket. Regardless of their type, all winepresses are capable of performing a variety of functions, and winemakers use them at different stages of the winemaking process. The reason why pressing is sometimes preferred over crushing is that it allows for better control over the quality of the juice when bitterness and astringency are to be avoided. With white grapes, pressing allows for quick removal of the juice and thus avoids any skin contact or maceration (fermentation of uncrushed grapes) effect.
In making red wines, pressing is usually employed when fermentation is completed or nearly so. After the free-run juice has been removed by siphoning it above the sediment level, some remaining wine is trapped within the mass of grape skins. The volume trapped, as much as 15% of the total yield, can represent a significant value to the winery. To separate the usable wine from the skins, the entire remaining mass (pomace) is pumped or shoveled from the fermenters into a press. This wine is known as press wine and is usually heavier, darker in color and more tannic.
Fermentation
Wine is a result of fermentation, a natural process in which the sugar in grapes is converted into alcohol and carbon dioxide through the action of yeast and other microflora. As soon as all available sugar has been consumed, the yeast stops working. This process also creates aroma compounds known as esters and flavor components known as congeners. Sometimes, sugar is added if there isn’t sufficient quantity in the grapes to achieve a desired alcohol level.
What we normally refer to as fermentation, winemakers call primary fermentation and lasts typically from five to seven days from beginning to end. During this process, temperature control is extremely important and different wine types are best fermented at different, rather narrow ranges. Secondary fermentation (called malolactic fermentation by winemakers) is a biochemical reaction different from the primary one in several ways. It is induced by bacteria and does not create alcohol. Instead, it involves a conversion of the acidity in the wine (called malic acid) to another kind of acid called lactic acid. Since lactic acid is much softer and smoother than malic acid, the malolactic fermentation is desirable in some wines (most U.S. red wines undergo this process as well as some whites such as Chardonnay and Pinot Gris). Winemakers can choose either to allow it to occur or prevent it from happening.
Clarifying
After fermentation, a range of particles, both visible and invisible, remain in wine – among the most common being spent yeast cells, protein particles, tannins, and grape skins. Clarification is the process of removing such particles from newly fermented wines so as to leave the wines bright, clear, and visually acceptable. The process; however, is necessary for more than cosmetic reasons. It also serves to remove many potential dangers and prepare the wine for bottling. Today, four clarification procedures are commonly practiced by winemakers throughout the world: racking, fining, filtering and centrifuging.
Racking is the oldest and the only truly natural system of clarifying wines. It is basically the process of transferring a wine from one container to another so carefully that only the clear wine is transferred, leaving sediment behind. It is probably the least efficient and removes only those particles that precipitate out from the wine naturally. Fining is one of the most widely used procedures and introduces an outside agent in the process. Fining agents (usually egg whites, gelatin or bentonite) absorb or adsorb particulate matter and are later removed themselves along with the unwanted substances by racking or filtering. Another property of fining agents is they make larger particles out of smaller ones, making them easier to remove. Filtering acts the same as a coffee filter and is one of the last procedures to be used to remove particles from wine. The purpose of filtering ids to remove yeast cells and other microbes, but it can also strip away positive constituents. Centrifuging is very costly, but because particles of all sizes can be removed this way, it easily replaces several rackings in winery operations and can make clarification simpler. Centrifuging involves spinning the wine in a vessel at such a high speed that particles migrate to the bottom of the vessel and are easily separated from the clear wine. It also enables winemakers to combine fining and clarifying in a single step.
Aging
Many wines are aged in wooden containers, but the fact is, not all wines are aged substantially or even partially, before bottling. Nor are all aging vessels made of oak. Quite a few wines are bottled just a few weeks or a few months after the harvest. In most instances, they will have been stored in stainless-steel tanks, not in oak barrels or could be aged in even larger wooden containers. Stainless-steel containers allow wines to marry and come together as they shed their youthful aggressive flavors and harshness. They do not impart any flavors from the vessel. Long aging of wine is rarely performed in stainless-steel tanks; however, wines are often kept in stainless-steel to prevent aging, by blanketing the top of each tank with carbon dioxide of nitrogen.
Most wineries wishing to age their wine prior to bottling will keep it in wood. They are wood-aged for several reasons. First, the process takes young “green” wines and replaces their roughness with softness and smoothness. Second, wines tend to evaporate slightly in wood barrels, thus concentrating the flavors. Third, as wine ages in wood, the alcohol and tannins leach out flavors from the container and these wood flavors are usually desirable. The shape and storage capacity of an aging container will be determined by its use within a winery. Generally, the smaller the container, the faster the aging process, and vice versa. Most winemakers prefer to start out using large containers for new wine and then complete the aging process with small barrels – a barrel containing either 55 or 60 gallons. Several wineries prefer using even larger oak barrels called a puncheon, which has a capacity of 135 to 150 gallons.
A brief word about new versus old oak and French versus American oak barrels. Use of any of these is totally up to the preferences of the winemaker and the flavors to be imparted in the wine. French oak tends to add more aggressive tannins, a slight perfumed aroma and sharp aftertaste. American oak is usually characterized as adding vanilla, spicy, creamy, or even lemony flavors. New versus old simply imparts degrees of the flavors mentioned above.
Blending
The blending of wines has almost been raised to an art form as winemakers strive to produce product, which meets a variety of consumer palettes. Blending, however, involves much more than just merging or mixing different wines. Winemakers blend by combining wines by region, by vineyard, by vintage, and by type of aging container. The purpose of blending comes down to creating a wine where the quality of the finished product is better than the sum of the components.
Combining two or more grape varieties is the most typical example of the act of blending. Many of the standard combinations now produced are classic blends originating in Europe, the best-known being from Bordeaux. This includes Cabernet Sauvignon, Merlot and Cabernet Franc, but may also include Malbec and Petit Verdot. The U.S version of this is often referred to as Meritage. The classic white Bordeaux wine includes Sauvignon Blanc and Semillon, with a small amount of Muscat as an option.
Winemakers discovered long ago, numerous other ways in which to blend for a better final product. Blending by region involves combining the same type of wine from different growing regions, such as Napa Valley and the Central Coast, or the same varietal wine from different Viticultural Areas within one county. In fact, some of the original vineyards in California were laid out to be “field blended.” That is, in this type of blend, the grape grower plants different varieties within the vineyards and makes the “blend” in the field. Needless to say, it makes it next to impossible to change the blend. In some areas of France, a version of blending takes place, but it is called co-fermentation. This technique combines two or more grape varietals that are harvested separately, usually a white and a red grape, and then fermented together.
In another blending technique, winemakers can use different cooperage to blend wines. The same grape is used, but the oak barrels they are fermented or aged in are different, each imparting a slightly different taste. Sometimes blends are created from both barrel-fermented and stainless-steel fermented wine. While others may be blends from barrels of different ages, or made by different coopers, or barrels made from different types of wood, etc.
One of the last ways to blend wines is a method, which is frowned upon in the U.S. That is, blending wines from different vintages (the year in which a wine is produced). Non-vintage Champagne is traditionally blended in this manner with excellent results. The only explanation for not routinely doing this in the U.S. is that it is easier to sell a vintage wine over a non-vintage one.
It is important to realize that blending has its place and that 100% of a single grape variety in a wine does not always insure a better quality wine. On the flip side, there are some wines, which simply do not seem to improve with blending. Chardonnays are one example of a wine, which doesn’t seem to improve with blending. Nor does Pinot Noir or Zinfandel (the red one). It has also been said that both Johannisberg Riesling and Gewürztraminer are too delicate to be blended, while in both Europe and the U.S. those wines modeled after the wines of Bordeaux, the Rhône Valley and Champagne, by their very names must be blended.
Bottling
Putting a wine safely into a bottle is the final step in the winemaking process, and this is no simple step. Bottling wines, over the centuries and more recent decades, has shifted from semi-primitive to clean and efficient to, in some instances, ultra-modern facilities as sterile as a modern hospital operating room. The primary purpose for this is to prevent tiny bacterium or yeast particles themselves, from entering the bottle.
Many large wineries have their own modern bottling rooms just for this process. High-speed processing lines are able to fill, cork and label over 1,000 bottles per minute! The smaller wineries “job out” bottling by trucking their wines to a contract bottler. But this can also be done in reverse. Instead of taking the wine to a contracted bottling facility, the bottling facility comes to the wine. A large truck pulls up next to the winery, a few hoses are attached, buttons pushed, and voila’, you have wine ready for market.
A few remarks about corks. The use of a cork to seal a bottle is shrouded in mystery. A cork is totally unnecessary for wines that will not improve with age in a bottle (which is a majority of wines produced). A cork became associated with quality years back, when screw caps first appeared and were scoffed at. Corks offer many advantages for protecting and aging wines, but they also cause problems because of their tendency to leak, to harbor bacteria, and to dry out when not kept moist. The “corky” odor and taste that afflicts some wines is actually due to a mold indigenous to cork, not the cork itself. Statistics show that nearly 3% of all corks have a defect, which could affect the wine. The best features about a cork are that it is compressible and adheres well to glass. Beyond that, they are terrible, and in my opinion ruin more good wine than is worth the “show” when opening a bottle of wine.
