It Ain't Easy Being Green

(Originally published March 2006)

The three of you who actually read Hanes's tasting notes may have noticed that he is no fan of the 2003 vintage in Europe. While, of course, there are exceptions the main flaw which troubles Hanes is that the unusually hot summer created an imbalance in the grapes. The heat caused incredible ripeness, particularly in terms of sugar accumulation. However, this sugar accumulation occurred at such an accelerated rate that the rest of the grape could not “keep up.” That is, the other chemical components in too many cases were not fully mature when the grapes had to be picked before the sugars got too high. Why did the grapes have to be picked? Because sugar converts to alcohol and the higher the sugar the higher the potential alcohol of the finished wine, sometimes much higher than desired. This immaturity was particularly true of the tannins in the red wine grapes grown in Europe in 2003, making the wine sweet and juicy as it enters the mouth but bitter and harsh as you swallow. Because of all this, Hanes thought this was a good time to discuss the topic of the physiological ripeness of grapes, “green” tannins and just what this all means.

Again, the foundational issues and problems. Sugars are converted into alcohol during the fermentation process. There are lots of things a winemaker can do both in the vineyard and in the winery to manage sugar levels. A LOT. We will go into some of these things but not all (Hanes's fingers get tired, after all). To achieve a wine that avoids too high of an alcohol level the winemaker may choose to stop the fermentation. This will leave some sugar unconverted into alcohol and make the wine sweeter. Sometimes this sweetness is desired. Sometimes it is just unavoidable given the need to control the alcohol. For our purposes here, we shall assume that the issue for the winemaker is alcohol management and not the desire to produce a sweeter wine.

OK, here we are back in the vineyard. The grapes are turning color, maturing, becoming ever so delicious and delightful. Here's where things start to get complicated amidst all this innocence and beauty. Ripe equals flavor equals more marketable wine these days. Concentration is good. Big is always better. What's a winemaker to do?

First, things like pulling leaves off the vines to get more direct sunshine on the grapes (direct UV light has a clear effect on the physiological ripening of grapes). Then cutting selected grape bunches off the vines to increase the amount of energy focused on the remaining bunches and allow for more even ripening among grapes and grape bunches. Cutting off bunches will result in less total wine in the end but the hope is that what is produced will be better and will fetch a high enough price to more than offset the lost income represented in the grape bunches rotting on the ground (hey, free fertilizer!). Another thing to do is push back the harvest to later dates so the “hang time” of the grapes are maximized, creating even more ripeness. Indeed, as the grapes hang longer and longer they will begin to dehydrate, this concentrating the sugars and flavors even more (but the grapes weigh less, which sucks for grape farmers who get paid by the grapes' weight!).

These techniques are employed mainly during what one could call “normal” weather (this said with the understanding that there are warmer and cooler climates where grapes are grown). No great rains, no hail, no weeks of 100 degree temperature days. But, ahh, what if the weather is not normal? What if there is a heat wave as there was during the European summer of 2003? If this occurs then all these techniques could cause problems, as they will contribute to an accelerated pace of ripening that is not desired. Now, usually people know there is a heat wave going on or expected. Duh. So they wouldn't pull leaves or such. You want sunlight to directly hit to grapes but if the nights are not cool enough to give the grapes a “rest” then some shading may be required. In the event of a major, prolonged heat wave there's little vineyard managers can do but closely monitor the grapes as the heat wave continues and try to ensure some kind of even ripening among the grape bunches. The game now is to try and watch things closely enough to hit the “sweet spot” when sugars are maximally in balance with physiological ripeness. Now, describing the latter is what interests us here.

As we've alluded to, the measurement of sugar levels was the primary factor in deciding when to pick the grapes. Over the past decades more attention has been paid to assessing the physiological ripeness of the pits and skins to achieve greater balance in the wine without sacrificing structure. This has been particularly true of hotter regions where the sugars elevate more quickly and haphazardly. The change in the phenolics (the name for the chemical compounds which account for color and tannins) as the skins, seeds and stems mature is difficult to measure. Compounding this is the variety of berry sizes among the different grape types, changing the ratio of skins-to-pulp and not allowing for a “one size fits all” approach to understanding phenolic maturity.

When discussing the physiological ripeness of grapes it is important to note that the “green” flavors and textures may come from external sources. The primary source is oak barrels, which can contribute up to 18 different phenolic compounds to wine. Different types of oak impart different flavors. And the seasoning of the oak can play a strong role in how much “wood tannins” effect the wine. Whether the oak is air-dried, dried in a kiln, or toasted with a flame will change both the kind of tannins left in the wood as well as their flavor. As will exposure of the oak wood to the sun, rain or wind during the seasoning. So there are some variables to consider beyond sucking on grape seeds when explaining green tannins. That said, the utilization of oak remains but one of the many external influences, with the majority of the human handprint on the wine exercised in the winery in order to manage the level and types of tannins left in the finished wine.

Grape skins do indeed contribute to tannins but their primary role is in producing color. Stems have lots of tannin in them but these days they rarely play a large role in the fermentation process (because they have tannins). So, it's the seeds we needs to discuss. In some grape types the seeds can have up to ten times the amount of tannins than the skins. Seeds usually represent 3% to 5% of the grape berry weight yet possess 49% to 69% of the total phenolic content. If the seeds do not reach full maturity there will be an increase in astringent tannins. The term for the tissue change in ripe seeds which crack when crushed is lignification. This bit of knowledge will never help you again. Physiological ripeness helps add “complex” tannins. If you could magically remove all the seeds from the grapes before crushing (be the seeds ripe or unripe) you would definitely have a fruitier, softer wine. But also a less complex wine and one less likely to age long enough to develop mature tertiary flavors (should those be desired). Complex tannins are good. Thus, the answer is not necessarily to get rid of seeds, stems, skins or any other possible source of “green” tannins but to strive to pick grapes with complete ripeness, both physiological as well as technological (the latter term describing the potential alcohol level and the acidity or the pH, especially as these relate to grape sugars).

After picking (out of necessity or desire), the relative physiological maturity of the grapes can be adjusted during the fermentation process. Extending or limiting the maceration period as well as controlling the temperature of the grape must before fermentation is a first step here. The process called “cold soak” maceration changes the ratio of anthocyanins (the compounds which effect depth of color) and tannins. Because skins have greater contact with the liquid during a cold soak there's more color extracted from the skins. The whole berries here, however, block the extraction of seed tannin because they remain trapped inside the berry with little if any liquid contact. All the winemaker needs to do is artificially lower the temperature of the room the grape must is in, low enough to inhibit the onset of fermentation. This can be for hours, days or weeks.

Once fermentation does begin and the solids rise to the top of the bubbling grape must, the winemaker can choose to “punch down” the solids back into the liquid to increase solid-to-liquid contact or instead “pump over” the liquid on top of the solids, letting it slowly seep downwards back through. Either technique has pros and cons for tannin management. It should be noted that higher alcohol content in the wine helps to dissolve the bitter seed tannins. This can be bad because these tannins are not like dissolved into thin air, they are dissolved into the wine adding bitterness to said wine.

Some people do like to remove as many seeds as possible before fermentation. The process of using whole fermenter racking eliminates many of these pesky seeds and their nasty old tannins. This fairly new process can make the concentration of tannins in a wine up to three time lower than without removing the seeds.

The lack of physiological maturity in grapes can become more evident if whole cluster fermentation is employed. This means the grapes are not destemmed and when the grape bunches are put in the fermentation tank so are the stems, maybe some leaves, all the grape skins and pits, the presence of all these adding to the potential tannin level in the wine. This approach adds structure but makes it harder to control the tannins. Especially if they be green. As a result, it is practiced mainly in cooler climate regions when overripeness is less of a regular issue and alcohol levels are generally lower.

A newer winemaking technique which effects tannins is called micro-oxygenation. This process is employed after fermentation and before malolactic fermentation and involves releasing a controlled amount of oxygen through wine (usually in the fermentation tank) at a rate at which the wine's phenolics absorb the oxygen without developing an undesired oxidative (flat) character. It introduces many changes to the wine, two primary changes being the softening of tannins and the bonding of anthocyanins to tannins which helps stabilize color. These changes might have occurred on their own naturally over time. We'll never know because winemakers are impatient cusses. Anyway, because grapes which have not achieved physiological ripeness are more astringent many winemakers want to change this aspect into a softer, rounder texture and mouthfeel. People who buy wine seem to like this (see, Hanes can spread the blame around!). “Micro” does this pretty well, accelerating the maturation process that, again, may have softened the tannins more naturally over years. An unresolved question remains how effective micro-oxygenation is with “green” tannins versus more mature yet still “hard” tannins. Hanes ain't no stinkin' winemaker so he don't know.

Then there are the two big bugaboos of contemporary winemaking, the “spinning cone” process and the “reverse osmosis” process. This screed is long enough so let's just cut to the chase and say these are two cutting edge technologies to adjust alcohol and water levels in post-fermentation wine, either by removing or adding alcohol or water. Whether this is “natural” or not, who is to say. But, speaking to the topic being discussed here, when grapes get super-ripe due to heat and/or longer hang time, to achieve more physiological ripeness one can reduce the resultant higher alcohol level through such technologies. Hence, less green tannins and, after some “massaging,” less alcohol too. All this without having to make a sweeter wine by leaving sugars uncoverted to alcohol during fermentation. The gods have indeed blessed us all.

The major upshots of all this is that in order to achieve a holistically balanced grape which will then translate into a harmonious, structured wine there's a zillion things to consider. Immature or “green” tannins have plagued winemaking since time immemorial. Each vintage will have its own unique character, a reflection of that year's weather and related circumstances. Should we just accept this as a poetic expression of the “will of nature”? Or, particularly as wine is a multi-billion dollar business, should we mess with the wine to make it as agreeable as possible? Ask your shrink, not Hanes. What Hanes will say is that one should never assume that warmer weather making riper grapes means better wine. But, hey, with the way global warming is going, one suspects that winemakers are intentionally raising the alcohol percentages in their wines to get you so drunk you'll ignore this inconvenient fact...