Article

Perfecting and Protecting Wine Color

colorBetter color. It’s a goal for just about anyone who makes wine, especially red wine — and most home winemakers make red wine at some time. Although not always directly related, wine color is often taken as a clue for wine flavor. A pale, watery-looking wine is expected to have light or mild flavor. Very often the relationship holds, so much so that home winemakers may feel the need to explain a light-colored wine as they serve it. When we make a wine that comes out too light for our expectations, or your red comes out orange or brownish instead of purple/red, or your white goes brownish, we wonder what we might have done differently to get the color that we are after.

Red Wines

Let’s focus first on red wines. As noted by the title of this article, a beautifully colored red wine comes about in two steps. First you need to get the intense color you want (perfect it), then you need to make sure it lasts in the bottle so it will be there when the wine is poured (protect it). Those two basic stages involve many decisions along the way. If you were to look for every contribution to color, you might include: grow better color, extract more color from the grapes, stabilize the color during production, add color to your wine, and hold on to the color during cellaring.

To consider the factors that go into developing a particular wine’s color, we will first review what wine color is. The principle pigments in red or black grapes belong to a class of polyphenolic compounds called anthocyanins. They are part of the flavonoid family, one of the large groups of grape and wine polyphenolic compounds. Tannins constitute another group of important polyphenolics in wine that also play a role in color stability as described later. Although the name anthocyanin represents the Greek phrase “blue flower,” the pigments themselves may be red, purple, blue, or colorless, depending on the pH. At low pH, red and purple forms dominate while higher pH’s favor blue and colorless forms. Making sure you have a pH in the desirable winemaking range of about 3.2 to 3.6 will help assure better color. While the pigments are found in colored plant tissues of all kinds, in most red wine grapes they are concentrated in the skins. There, and in the pulp of the few red-fleshed varieties (such as Alicante Bouschet), the pigments exist as sugar-bound structures (glycosides) in vacuoles (membrane-enclosed units) within plant cells. To get in the wine, they need to be released from the grape tissues and stabilized against oxidation or precipitation. Before that, though, they need to develop in the ripening grapes.

Red Means Ripe

Viticulture researcher Dr. Richard Smart edited his groundbreaking book Sunlight into Wine with Mike Robinson in 1991. Built as a series of essays on the techniques and effects of grapevine trellising, it was one of the major viticultural works of the late 20th century and it continues to influence grape growing today. Smart cited research from a variety of sources that proved open grapevine canopies, allowing more air and — critically — more sunlight to reach ripening grapes, could profoundly improve the crop. Not only were yields higher with open canopy designs, but fruit color and wine quality improved as well. Sunlight falling directly on the fruit or only lightly filtered through vine leaves leads to a denser concentration of anthocyanins. Smart’s rule of thumb is that, on average, there should be one to one-and-one-half layers of leaves between the sun and the grapes as the fruit is maturing. If you grow your own grapes, or influence the work of your grower, you can check this during the growing season. Insert a thin rod at random into the canopy to touch a grape cluster. Count the number of leaves the rod passes to get to the grapes. Write it down, and repeat at least ten times at random around the vineyard. The average from those counts will tell you how close you are to Smart’s ideal.

There are long-term and short-term techniques to improve sunlight penetration in the canopy and improve grape color. In the long term, as when planning a vineyard, read books like Dr. Smart’s to help you choose a trellis design that will be open and airy given your climate and selected variety and clone. For existing vineyards, consider leaf-pulling as a management technique to improve color. Several times during the growing season, examine the canopy. Remove leaves in the fruiting zone if excessive shading is occurring.

The crop load on grapevines also affects the color intensity. When overcropped — burdened with too much fruit — the vine will not ripen the grapes effectively and the color will be less intense. (There will also be green, grassy or bell-pepper flavors and aromas, but here we are concentrating on color.) For this condition, too, there are long and short-term techniques to apply. As you prune the vines in the winter, limit the number of buds to the quantity of clusters that your vines are able to fully mature within your growing season. Since bloom quality and fruit set can vary from year to year, check again as the season progresses. At veraison (the color change from green to red), go through your vineyard and cut off clusters wherever the crop looks too heavy for that particular vine. Also drop fruit that is obviously greener than most of the crop; if left, it will likely be less ripe but difficult to detect at harvest. If you drop fruit much before veraison, it may stimulate the vines to bloom again and produce useless “second crop” grapes that will not be ripe in time for harvest. Thinning at veraison reduces the likelihood of repeat blooming. Finally, at harvest, look for full physiological maturity in the grapes for best color. Either go through and drop immature fruit before harvest, or sort out any clusters with light-colored berries and discard them at the crusher. For best color, don’t get greedy!

Color After Crush

Once you have harvested and sorted your grapes, it is time to macerate. After crushing and destemming, a cold soak can help get anthocyanins out of the skins and into the juice. In his book Techniques in Home Winemaking, Daniel Pambianchi recommends using sealed bags of ice or frozen jugs of water directly in the must to hold a temperature of less than 46 °F (8 °C) for as long as seven to ten days if you choose to cold-soak. Adding about 50 ppm (parts per million) of sulfur dioxide will help retard spoilage and prevent spontaneous fermentation. Daily stirring and replacement of the ice will be needed to keep the temperature uniform and to facilitate the color extraction. At the end of your cold soak, allow the temperature to rise before inoculating with yeast.

After (or without) a cold-soak, there is a range of enological products you can add to improve color extraction and stabilization. The most direct of these are the macerating enzymes. This is a step I take every harvest to get more color in the Pinot Noir wine I make from my cool-climate backyard vineyard. There are several choices, such as Lallzyme EX, Scottzyme Color Pro, and Enartis Color Plus. While primarily containing pectolytic enzymes (pectinases) to break down pectins in the fruit, the enzyme preparations also have important secondary effects from cellulases, hemicellulases, and proteases that help break structural components of the cells. The result is release of not just more anthocyanins, but more of other polyphenolics as well, such as tannins. That turns out to be important for color stability. Tannins form condensation reaction products with anthocyanins that are more stable against precipitating out or becoming oxidized. Enzymes that facilitate the release of anthocyanins and tannins improve both color yield and stability. Enzymes are usually dissolved in distilled water and added to must soon after crushing (follow manufacturer’s directions for the product you choose).

Because of the role of tannins in color stability, it may also be helpful to add tannins during fermentation. This especially holds true for low-tannin varieties such as Pinot Noir or Sangiovese, but I have successfully made such additions to much more intense varieties like Cabernet Sauvignon and Syrah. Products like Scott’Tan FT Rouge Soft or Enartis Incanto N.C. are derived from a variety of wood sources. Their tannin components react with grape anthocyanins to stabilize color. Oak chips or dust may sometimes be added to a primary fermentation for similar tannin binding effects. The simplest method for introducing enological tannins to your fermentation is to simply scatter the powder on top of the must at the time of the first punchdown.

The first punchdown is also the opportunity to add another class of color-stabilization products: yeast derivative nutrient products (related to common yeast hulls). For these products, like Opti-Red® from Lallemand or Pro Tinto from Enartis, the inactivated yeast residue is refined in a process that leaves in place a high concentration of polyphenol-reactive polysaccharides (sugar chain molecules). Introduced into the red must, the nutrient product polysaccharides bond with grape anthocyanins to stabilize and preserve color. I have been using these products in my red wines for several years and I am very happy with the results. Classed as nutrients and derived from yeast, they do not contribute enough nitrogen to replace your normal nutrient addition program, so continue with whatever you currently do in that area.

Along with using products like those I just mentioned at first punchdown, you will also choose a yeast strain. If color improvement is a major goal, you can address it with this decision. When producers of wine yeast publish the characteristics of each strain, color stabilization is one of the factors listed. For instance, among the 16 strains of active dry wine yeast distributed by The Beverage People in Santa Rosa, California (where I work and am a partner), seven of them are marked as stabilizing color. When choosing your yeast for other characteristics, you can also select for color stabilization.

The next step is active cap management. As the grape skins inflate with carbon dioxide and float to the top, you need to somehow get them in contact with the fermenting juice for best color extraction. Punching down the cap is a technique used by many home winemakers. Twice a day (or perhaps three times a day for maximum extraction) a tool like a large potato masher is used to push the floating cap down into the fermenting juice and make sure everything is well mixed. Another technique that is considered gentler for tannin extraction but still very successful for color is rack-and-return. For this process, the fermenting wine is drained from the tank, the cap settles to the bottom, and the skins are allowed to drain for a while. The wine is then rapidly returned to the tank, breaking up and mixing the cap. Commercial winemakers have other techniques for effective cap management including pump-overs and rotary fermenters, but these are not usually available to home winemakers. Whatever you do, make sure you mix the cap and the wine frequently and thoroughly for best color yield.

Most of the color in red wines is extracted in the first few days. Pambianchi notes that the intensity then drops off and levels out after about one week. Other polyphenolics, like tannins, will continue to extract over a more extended period. That implies that for color alone, you may want to consider pressing early and finishing your fermentation in carboys, tanks, or barrels. Other considerations, like a suitable tannin profile for mouthfeel, may incline you toward going all the way to dryness. Beyond that stage, you may encounter advice for an extended maceration or post-fermentation soak. While that may be effective for tannin management and rounding out mouthfeel, it is not generally considered beneficial for color extraction and color may fade during such a period.

Adding Color

Now let’s discuss color addition. Of the several ways to introduce more color, none include artificial colors or synthetic dyes. Instead, they involve grapes or grape products. Perfectly natural, and widely accepted in commercial winemaking, is the simple blend of darker grapes or wine with your base production. The blend may take the form of darker grapes added as a minority of the must right from the start, blending young wines before aging, or blending finished wines for bottling (see my article on blending like a Super Tuscan in the February-March 2016 WineMaker for more details on that subject). A bit less common, but still viable, is to add a small portion of a dark grape concentrate to a base wine. That can be done at primary fermentation or, if you finish a young wine and still think it is too pale, you can add a concentrate and referment for more color. I have successfully added Petite Sirah concentrate to one batch of Pinot Noir and Zinfandel concentrate to another. On the commercial side of things, the controversy starts with products like Mega Purple and Ultra Red. These are grape concentrates prepared from teinturier grape varieties — those with red flesh and juice — like Rubired or Alicante Bouschet. By proprietary processes that may include fractional distillation and solvent extraction, manufacturers make very dark grape concentrate that can be added in small amounts to improve color. Typical addition rates in commercial wines range from as low as 0.04% (0.4 g/L) to perhaps as high as 0.5% (5 g/L). Additions made prior to fermentation are well integrated and generally not very controversial, since they are a lot like adding ordinary concentrate or even adding some dark grapes directly. It is said, though, that for many wines selling for less than $20 per bottle, there is a color adjustment done after the wine is finished. Since Mega Purple is around 68 °Brix (percent sugar by weight), even a small addition after fermentation may add perceptible sweetness. Since the products sell for about $135 per gallon, and that one gallon would treat 200 gallons of wine at a (high) 0.5% rate, they may not be practical for most home winemakers.

The final stages of stabilizing color come in the aging process. In barrels, or using oak alternatives like sticks or cubes, further condensation of tannins with anthocyanins may occur. In the case of barrel aging, there is also a slow addition of very small amounts of oxygen. Protected from gross oxidation by regular maintenance of sulfur dioxide levels and topping up, the wine in barrel will nonetheless gradually shift from bright red to more muted, tile-like colors. Those colors tend to be more stable over time than the bright red color of young wine, so your objectives for your wine come into play. If you like it bright red and intend to drink it young, use a short aging period in glass or stainless steel. If you like the color of mature red wine, age in oak for a longer period. That will also produce a wine likely to hold its color in bottle for years.

White Wines

The first rule of white wine (and rosé) color is: avoid browning. Consumers of white wine are looking for clear, light, straw-colored wine, with a maximum color appearance of yellow or gold. Generally, white grapes and juice contain no anthocyanins, and negligible tannins than their cousins the red and black grapes (with a few exceptions, which we will discuss in a moment). Nonetheless, there are enough such compounds that some of the long-aging effects on red wine color can occur, even in a short time, in white wine. Oxidized polyphenolic compounds like those giving a “tile” color to old red wine can develop in young white and rosé wine (or even juice) with excessive exposure to air and the resulting oxidation. The difference, though, is that in whites, phenolic acids are converted into their brown-colored quinone forms. In reds, it’s those tannin-anthocyanin complexes that oxidize into the quinone forms. When making white and pink wine, employ a two-prong attack on oxygen damage: minimize contact and neutralize the effects. The first step means process the grapes quickly, make transfers by siphon or pump rather than pouring, and ferment in closed containers that will accept an airlock. Carboys and stainless steel tanks are most common, although barrels are sometimes used for Chardonnay (and a bit darker golden color is acceptable in that varietal than in many other whites). Do not use an open fermenter such as those used for red wine. For the second step, control temperature and use sulfites. Keep everything as cold as you can while working with your white grapes and juice to prevent browning. Also use sulfites consistently. Add about 50 ppm of sulfite at the crush and more if there is any sign of damage on the grapes. If you chill and rack the juice, do so in a tightly closed container. As soon as primary fermentation is finished, add sulfites again (except if inducing malolactic fermentation, again almost exclusively Chardonnay). Keep sulfite levels up throughout aging. At a pH of 3.5, where a red wine would need 25 ppm of free SO2 for protection (a “molecular” SO2 level of 0.5 ppm), a white wine needs 40 ppm free (molecular 0.8).

There are a few specific instances where other colors come into play with white wines. In particular, Sauvignon Blanc juice has a tendency to “pink.” The color of the freshly pressed juice turns pink on exposure to air. If the color persists in the wine, it is considered undesirable by consumers. A fining with polyvinylpoly-pyrrolidone (PVPP or Polyclar™) will remove the pink color with little effect on the other wine characteristics. Color may also appear from the grapes themselves. Certain “white” varieties have distinct pinkish or purple notes in the skins, most notably Pinot Gris/Pinot Grigio and Gewürztraminer. If you are not careful, such grapes may produce wine with an unattractive “bronze” hue. When making white wine from grapes like these, minimize skin damage and contact. If you have a bladder press or hydraulic press, try whole-cluster pressing to minimize tearing of the skins. If you have a manual ratchet press, you will probably need to crush before pressing to get an acceptable yield of juice. If so, transfer the must quickly to the press and avoid soaking. Again, work as cold as you can and use sulfites.

Control Color

So there you have the entire “life cycle” of color in red wine, and the best practices for preserving color in whites. When making red, get the color via the grapes in the first place, enhance its extraction while you make wine, add more color if you want to, stabilize whatever you get, and age it in a manner to achieve your objectives. From personal experience making Pinot Noir for about 15 years, I can tell you there is no better teacher for color development than making wine again and again from a light-colored variety. For whites, minimize browning, be diligent about oxygen exposure, keep on top of SO2 additions, and keep your temperatures cool!