Basics Of Winemaking

Basics of Winemaking

Fine wines are often vinified in smaller lots than are tables wines produced for mass consumption. Thus, the fine wine producer works with smaller batches of grapes and processes and ages them in smaller fermentation, storage, and aging vessels. This allows the winemaker to lavish greater care and attention on the wines and utilize techniques to promote quality that would be impractical or cost-inefficient for modestly-priced wines produced in larger quantities. Listed below are the standard steps in the vinification process for white and red wines, with a brief discussion of how fine wine techniques may differ from standard vinification protocols.

White Wine Vinification

Crush & Destem

After the grapes arrive at the winery, they are mechanically crushed and de-stemmed. This releases some free run juice, and separates the fruit from the stems, which can impart bitter tannins to the juice. Some wineries forgo the crush/destem step and send the grapes immediately to tank presses, which gently squeeze the juice from the skins and minimize the extraction of tannins from skins and seeds. In general, the fine wine objective is to maintain the integrity of the free run juice, minimizing the extraction of bitter phenolic compounds from the skins, stems and seeds.

Press

In white wine processing, after crushing and destemming the grapes, the must (the mass of unfermented juice, skins, and seeds) is immediately pressed, in one of a variety of mechanical presses, to separate the juice from the skins. Some winemakers, wishing to extract more flavor and body, may allow the juice to remain in contact with the skins for a few hours, but this runs the risk of imparting astringent tannins to the juice as well as other unwanted elements, such as sulfur dust from the vineyard. The quality of the press and the degree to which it “macerates” the skins and juice, will affect the quality of the resulting wine. The best presses rely on gentle pressure to extract the juice from the skins.

Primary (Alcoholic) Fermentation

During the primary fermentation, the natural sugars of the grape juice are converted to alcohol and carbon dioxide through the action of either cultured or native yeasts. The former are bred in a laboratory to accentuate certain positive attributes while the latter grow wild in the vineyard on the skins of wine grapes. Although most winemakers employ cultured yeasts, which more reliably produce “clean” fermentations and desired aromas and flavors, some fine wine producers rely on natural yeasts, believing they promote more complex characteristics in the wine.

Most white wines, including inexpensive chardonnays, ferment in stainless steel tanks, which are inert, easy to clean, and facilitate control of the fermentation temperature. These wines ferment at cool temperatures – usually around 55o F. – to best extract their fresh, fruity qualities. However, many fine wine producers ferment chardonnay in small oak barrels, a technique long practiced in the Burgundy region of France. Fermentation of white wine in barrels (normally French oak for chardonnay), because it occurs at higher temperatures, allows air to reach the wine, and imparts phenolic and flavor extracts from the barrel, alters the aroma, texture, and flavor of the wine, in the direction of greater richness and complexity.

Secondary (Malolactic) Fermentation

Winemakers who barrel-ferment their white wines often put them through a secondary fermentation, common to virtually all red wines, in which the malic acid naturally occurring in wine grapes is converted into lactic acid. This occurs naturally or through inoculation of the wine with malolactic bacteria, which require a relatively high-temperature, high-pH, and low-sulfur environment in which to grow. Because malic acid is a “hard” acid and lactic acid a “soft” acid, the conversion creates a softening of the wine’s texture. It also produces a chemical called diacetyl, which expresses itself as the buttery aroma and flavor many chardonnay lovers treasure.

Aging

The purpose of aging is to allow a wine’s aromas and flavors to develop before it is bottled. Aging in stainless steel tends to preserve a white wine’s fresh, fruity characteristics, while aging in barrel promotes the development of secondary characteristics through slow oxidation and the extraction of barrel tannins, aromas and flavors, such as spice, toast, and vanillin. Fine wine producers who ferment white wines (usually chardonnay) in barrels (usually French), and put them through a secondary, malolactic fermentation, sometimes also age those wines sur lie (French for “on the lees”), meaning the wine is allowed to remain in contact with the yeast cells that die during fermentation and settle to the bottom of a tank or barrel. This contact with the dead yeast cells imparts a “bready” aroma and creamy texture to the wine, an effect accentuated by periodically stirring the dead yeast cells to circulate them throughout the wine.

Clarification

Virtually all winemakers want their wines to be cosmetically appealing – i.e., clear of any haziness that may be caused by residual particulate matter. Several techniques are used to accomplish this: racking (removing the wine from the sediment that settles at the bottom of an aging vessel and transferring it to another container); fining (introducing an agent such as egg white, gelatin, bentonite, isinglass or casein, which adheres to particulate matter in the wine and carries it to the bottom of a tank or barrel); and filtration (running the wine through a pad, diatomaceous earth, or membrane filter to remove suspended particles). Both fining and filtration, which are also used to remove unwanted microorganisms and reduce tannin levels, can strip aroma and flavor from a wine, so fine wine producers normally opt for natural clarification (racking), when possible, or minimal fining or filtration, when necessary.

Bottling

The winemaker’s greatest concern during bottling is to protect the wine from oxidation. Toward this end, modern bottling lines purge oxygen from the empty bottles prior to filling and automatically calibrate fill levels to minimize the head space in the bottle between the wine and the cork.


Red Wine Vinification
The production of red wine differs from that of white wine in the following ways:

Fermentation

Unlike white wines, the juice of red wine grapes ferment in contact with their skins. (The skins impart a red wine’s color and tannin.) After crushing and destemming, the must – juice, skins and seeds – is inoculated with a cultured yeast and fermentation ensues, for a shorter duration (7-10 days) and at appreciably higher temperatures (75-85o F) than for white wines, to efficiently extract color, tannin and alcohol. During the fermentation, the release of carbon dioxide pushes a “cap” of skins and seeds to the top of the fermenter, and the winemaker has several methods available to continue macerating (mixing) the juice with it. Conventionally, this is done by periodically pumping juice from the bottom of the tank over the cap. However, fine wine producers, to enhance the extraction of color, flavor, and tannin from the skins, often prefer to punch down the cap in order to submerge it in the juice, or even to drain the juice from the tank and then splash it back over the cap to encourage greater circulation of the cap throughout the juice (a technique known as “rack and return”). Whatever method is chosen, fine wine producers often extend the maceration period beyond the end of fermentation to foster the full extraction of color, flavor and tannin. Once this process is complete, the new wine is pressed off the skins and moved to wood containers, usually small oak barrels, to commence the aging process.

Aging

Red wines normally spend a longer time aging in wood – anywhere from a few months to several years - than do whites, because they take a longer time to develop. In particular, extended barrel aging allows the tannins of red wines to soften and the fruit in the wine to emerge in response to the gradual oxidation allowed by barrel aging. As with white wines, extracts from the wood itself contribute to the aroma, flavor and texture of the wine, with newer and smaller wood containers (50 or 60 gallon oak barrels) imparting more wood character (and thus dictating a shorter wood-aging period) than older and larger containers (135 gallon puncheons or larger upright tanks). The winemaker must also match the type of wood and its “toast” level to the varietal; in general, fine wine producers prefer French oak for French varietals like cabernet sauvignon, merlot and pinot noir, while American oak works well with zinfandel. The former imparts a toastier, spicier character to the wine, while the latter is associated with a sweet vanilla aroma.