sunday schoolHow’d They Do That: Winemaking Part I: Red & White Wines

July 4, 2021by Terrell Abney

Join us each Sunday for an ongoing series of articles exploring the world of wine, which complements our monthly Corners Collection. July’s Collection is, fittingly, titled, “How’d They Do That?”. This week, we begin discussion of key wine making processes and techniques. Join us each Sunday in July to get to know how your wine was made. 

The French notion of “terroir,” that wine tastes of a place and all the influences that “place” brings to the growing of grapes, often finds expression in the phrase, “wine is made in the vineyard, not in the winery.” In fact, this notion is so central to the French philosophy of wine that, surprising as it may be, there is no word for “winemaker” in French. Rather, the word most often used for a winemaker is “vigneron”–meaning “wine grower.” 

Indeed, great wine is made in the vineyard, but, to be sure, there are influences affected by the winemaker (even in the most “hands-off” approaches) that contribute to the final product in your glass. Our “How’d They Do That” article series focuses on some essential winemaking techniques–and the most sensible place to begin such a discussion is with the general process for making white and red wines.

This discussion of the general winemaking processes begins after harvest, but rest assured that a great deal happens to get us to this “starting” point. Most of the steps in the process for production of still (non-sparkling) white and red wines are very similar, although they may not necessarily happen in the same order. This variance in procedure between white and red wines is due in large part to the fact that all grapes (save for a very few varietals) have nearly clear juice. 

This means that any color in a wine (except for wines from those few odd, red-fleshed grapes, which you are very unlikely to encounter) comes from the skins. The skins are also the primary contributors of tannin (the astringent substance that makes some red wines feel drying to the mouth), but tannin can also come from grape seeds, grape stems, and wooden barrels. In this article, we will walk through the general process for the production of still, white wine. Discussions of still, red wine production as well as sparkling wine production will be saved for subsequent articles.

BEFORE FERMENTATION: CRUSH

The pre-fermentation phase is often referred to as “CRUSH”–even (inexplicably) when the grapes aren’t actually crushed.

SORTING

Sorting to remove damaged and/or under-ripe or over-ripe fruit, leaves and other debris, and any array of “MOG” (materials other than grapes–you would be surprised as to what all that might include) may be done entirely by hand, fully by automation, or as a combination of both. The greater the degree of hand-sorting utilized, the higher the cost of production will be.

CRUSHING

Crushing is the process of breaking open the grapes (often called “berries”) so that the juices are released. Crushing is a different process than pressing (which will occur later in the process). In fact, crushing often does not occur at all in white wine production. Along with crushing, destemming may (or may not) occur. 

Crushing is often skipped for white wines to reduce the contact between the juice and the skins (and thus reduce tannin), but may occur for the production of wines from aromatic grapes such as riesling, gewürztraminer, or albariño, or for the production of “orange” wines (more on this in a moment). 

COLD SOAK/MACERATION

Maceration of the must (the mix of grape juice and grape solids resulting from crushing) is one of the key differences between white wine production and red wine production. During maceration, the grape juice is in contact with the grape skins (as well as the seeds and, if included, the stems). It is during this process that pigment, as well as tannins and a number of flavor compounds, is extracted from the solids and brought into solution with the juice. 

Maceration occurring prior to fermentation is called “cold soak,” as the must must be chilled to prevent fermentation. At this point, the must is largely water, which is a rather limited solvent. 

For greater extraction of color, tannin, and flavor compounds, a winemaker may choose to macerate the must during and/or after fermentation, as alcohol is a much more effective solvent. Cold soak/maceration is usually reserved for red wines, but a winemaker may elect to allow a “white wine” to have a cold soak/maceration period for the production of so-called “orange wines.” Ramato style pinot grigio is a classic example of such a treatment. 

A very brief period of cold soaking (typically no more than 24 hours) may also occur for production of aromatic white wines, so that the phenolic compounds responsible for the aroma/flavor of these wines can be extracted from the skins. Of course, such soaking/maceration would require the crushing of the grapes to release the juices.

PRESSING

Pressing is the next key difference between white wine production and red wine production–not so much whether it happens as when it happens… For white wines, pressing would typically occur at this point.  Even if the grapes have not been crushed (as is probably the case with white wines), some of them will have burst by the point when the grapes are loaded into the press mechanism. The juice resulting from these broken grapes is referred to as “free-run” juice and is generally regarded as the highest quality juice–as such it may be kept separate from later, pressed juice.  

Pressing may be performed between hard surfaces, as with antique wine presses, or with more gentle, bladder-style presses, in which pressure is created by a balloon or bladder filled with air or water. Multiple pressings may occur, with each pressing yielding decreasing valued juice. The solids remaining after pressing are referred to as “pomace” and are often plowed into the vineyard, but may also be used to produce brandies, grappa, marc, or (in Champagne) ratafia.

MUST ADJUSTMENTS/JUICE SETTLING

In some cases, the winemaker may elect to make adjustments to the must/juice, particularly in terms of acid, sugar, or tannin levels–but such adjustments are not permitted in many appellations. Most adjustments (assuming that there are any, and provided that they are permitted) may occur following crushing or pressing. Whether or not must adjustments have been made, the juice may be allowed to settle (“débourbage” in French) in order to allow adjustments to integrate, allow solids to precipitate, or to allow for preparation of or more grapes or preparation of the fermentation vessel.

ALCOHOLIC FERMENTATION

Fermentation is, according to Merriam-Webster, “the enzyme-catalyzed anaerobic breakdown of an energy-rich compound by the action of microorganisms that occurs naturally and is commonly used in the production of various products. . .” Alcoholic fermentation is one type of fermentation and is a rather complicated series of chemical reactions. In order to skip the organic chemistry level details, we can simplify the overall process by saying that yeast cells metabolize sugar molecules in such a way as to produce ethanol, carbon dioxide, and heat. In most cases, most of the fruit sugars will be converted into ethanol, but some may be broken down into other alcohols, glycerol, a number of different acids, acetaldehyde, or ethyl acetate–of course, some sugars may remain unconverted.  Essential steps in the alcoholic fermentation process include:

INITIATION

Fermentation may often be initiated spontaneously, by naturally occurring yeasts that have collected on the grapes. Such spontaneous fermentation by natural yeasts can be a bit unpredictable, especially in areas without an established wine history. In most cases winemakers will use commercially produced strains of yeast to start fermentation in a more controlled manner and yield more predictable results. 

In such cases, the winemaker will elect to either add sulfur, which kills not only the naturally occurring yeast, but also any fungi or bacteria present, or refrigerate the juice/must, which slows (or even stops) the activity of the yeasts. The primary strain of yeast used is Saccharomyces Cerevisiae, but other strains may be selected to influence the fermentation process or the resulting wine in various ways. 

FERMENTATION

Once yeast has been introduced to the juice of the grapes (either naturally or in a controlled fashion), the series of reactions that cause the alcoholic fermentation will be under way. As fermentation proceeds, heat is created, which, left untended, will increase not only the speed of fermentation, but also the temperature of the juice/must. If fermentation temperatures are allowed to pass 60℉, the fruit and floral tones of the wine may be compromised. The resulting wine may taste of cooked fruit or simply be neutral and non-descript. 

At the extreme, the exponential increase of heat and speed will reach temperatures (exceeding 100℉)and/or alcohol levels which will kill the yeast cells and end fermentation (often before fermentation is complete). With these risks in mind, one of the most important tasks of the winemaker during the fermentation process is to control the temperature of the fermentation.  Temperatures in the range of 50-60℉ are ideal for most white wines, as this range helps to preserve the fruit and floral character of the wine. 

CESSATION

Fermentation will cease naturally once all of the fermentable sugars in the juice/must has been consumed (leaving no food source for the yeast) or once alcohol levels reach much more than 14% (killing the yeast). The winemaker may choose to halt the fermentation earlier than it would naturally end, often by cooling the wine, but ending fermentation in this controlled fashion may result in residual sugar in wine. Once fermentation stops (either naturally in a controlled fashion), the liquid in the fermentation vessel is wine–but there are still a few more things to do. . .

AFTER FERMENTATION

There are a number of optional processes between the completion of fermentation and bottling. Most producers will utilize some, but not all of the options discussed below:

MALOLACTIC FERMENTATION

Malolactic fermentation (MLF) is another example of the biochemical processes known as fermentation. In this case, rather assertive malic acid (the same acid in a Granny Smith apple) is converted into gentler lactic acid (one of the acids in yogurt, cottage cheese, and sourdough bread). In the process, a compound called diacetyl is also created. 

Diacetyl is responsible for the “buttery” character of many chardonnays. Chardonnay is one of the few white wines that regularly undergo malolactic fermentation–but not all chardonnays are subject to this process. Malolactic fermentation is generally avoided for wines in which crisp acidity, lighter body, or vibrant aromas are desired. Malolactic fermentation can occur following or during alcoholic fermentation.

LEES CONTACT/SUR LIE AGING

Following alcoholic fermentation, the spent yeast cells (known as “lees”) will begin to settle to the bottom of the fermentation vessel. For many wines, the wine will be removed from the vessel in a gentle manner known as racking, so as not to disturb and redistribute the yeast cells. Some wines, however, are allowed to remain in contact with the lees for a period of time. 

During this aging sure lie (on the lees) the settled lees may be redistributed into the wine by stirring (also called battonage). Gradually, the lees decompose and impart their aromas as well as a creamy texture to the wine.

ADDITION OF SULFUR

Sulfur may be added at any point in the process, but is usually done very sparingly to prevent spoilage, browning, or resumed fermentation (in the event that there is residual sugar). Excessive use of sulfur can lead to a number of wine faults.

CLARIFICATION/RACKING/FINING/FILTERING

A newly fermented wine will be a cloudy (and rather unattractive) proposition. As a result, most wines will be “racked”–a process of allowing suspended solids to settle to the bottom of the vessel and then gently removing the wine. Racking may be performed several times, with each racking resulting in a clearer wine. Wine may be further clarified by fining or filtering. In fining, an agent will be added to the wine to bond to either proteins or tannins suspended in the wine. The now heavier particles will gradually fall out of suspension and the wine can be racked, as described above. Some fining agents are animal products (gelatin, egg whites, casein, isinglass) and are not suitable for use in vegan wines. 

Filtering is a clarification process that involves passing wine through a porous device, thus removing particles that are too large to pass through the openings of the device. Filtering is often used to remove microbes (particularly yeast and bacteria). This can be particularly helpful if alcoholic fermentation was halted before all of the sugar was consumed by the yeast, as fermentation may resume in the bottle; however, filtering does run the risk of removing desirable flavor compounds from the wine. Wines that have not been fined and/or filtered may contain sediment or appear slightly cloudy. This is not considered a flaw, but simply a production choice.

BARREL AGING

Aging wine in a wooden barrel may affect two changes to the wine. First, the wine may pick up flavor and aroma compounds from the barrel. This may result in notes of vanilla, baking spices, coconut, and/or dill, depending on the type and origins of the wood and the age of the barrel (with newer barrels imparting more flavor/aroma). Secondly, the barrel will allow for slow oxidation of the wine. While oxygen is generally damaging to wine, slow and gradual exposure can help to add complexity to the wine. Barrel aging for white wines is generally reserved for fuller-bodied styles of chardonnay and sauvignon blanc.

BLENDING

Blending is the process of combining several wines into one integrated wine. The wines used for blending may come from different grapes, different vineyards, different vintages, or different winemakers. Blending may be employed to create a more complex, more interesting, and/or more balanced wine, but it may also be used to create a consistent, reliable flavor profile (as is often the case with branded wines).

COLD STABILIZATION

Newly fermented white wines can be rather high in tartaric acid, which cannot (and should not) be removed by filtering. At colder temperatures, tartaric acid will crystalize. These crystals (known charmingly as “wine diamonds”) may fall out of solution or collect on the bottom of the cork. They are not considered a fault, but many consumers assume them to be such. As such, many producers will opt to “cold stabilize” white wines by chilling them to around 25℉ for several weeks and then rack the wine off of the precipitated crystals.

These are the processes that are most likely to be used for the production of white wines. Each one of these processes requires decision by the winemaker–and each will affect the wine that eventually finds its way to your glass. Over the next few weeks, we will discuss other vinification (winemaking) processes and techniques, including processes used for the production of red wine and sparkling wines. Each of these discussions will help you to have a greater understanding of how each wine has been produced–and how these decisions and processes have affected the final wine.

by Terrell Abney

Terrell Abney is a Certified Specialist of Wine (CSW), Society of Wine Educators and Wine Buyer at Corners Fine Wine & Spirits in Peachtree Corners, GA.