Waiting for the lees to settle.

Waiting for the lees to settle.

This morning, I peeked in (read: “removed stoppers and sniffed the wine”) on my 2011 Montepulciano and I am hard pressed to say there was any sign of Volatile Acidity. In a few days, after the lees settle some more, I’ll test and taste, then rack.

In the meantime, I wanted to talk about the changes a wine goes through during the initial part of the élevage; the primary fermentation.

I think there is an image most casual wine drinkers have of the winemaking process and how the fruit and wine look, taste and smell during the process. Most of the time, that involves picture-perfect, pristine fruit, vibrant colors, an elegant dance of fruit in clear juice as invisible yeast cells extract color and flavors and lovely aromas. This is probably driven by well-edited, PR-generated photographs.

It’s not that the smells, flavors and images of winemaking are utterly revolting to the senses. It’s a bit more nuanced than that.

Fiano after pressing and after fermentation.

Fiano after pressing and after fermentation.

Most people don’t realize that the color of wine undergoes a significant metamorphosis from crush to bottle.

Take white wine: The grapes are pressed just after they are picked. Many varieties start out looking like tea with milk. Others can be very green, but still very cloudy and murky.

The settling of particulates before, during and after primary fermentation does a lot to the color and clarity of any wine. It is possible that yeasts may also contribute to a change in a white wine’s hue – but I am not certain of this.

After primary and secondary fermentations, filtering clarifies and polishes the wine to a sparkle.

There is some talk about filtering “stripping” flavors from a wine. This is not supported by what we know about the filtering process: The tightest filters have an average pore that is smaller than the size of a yeast cell. These filters are used to sterile filter wine.

Flavor and aroma molecules are much smaller than a yeast cell.

Knowing these facts, one is hard pressed to believe that filtering removes some aromatic or flavor component from a wine.  It IS entirely possible, however, that the filtering process in some instances can introduce oxygen into the wine. In which case, the wine can change – but as a result of oxygenation and not because of “flavor stripping”.

There is one other change in the sensory characteristics of a wine that may come about as a result of filtering – particularly with fine filters: Texture. It is conceivable that minute particles, which contribute to the texture and possibly sense of weight of an unfiltered wine, can be removed in the filtering process. Texture, however, is not taste or flavor. These are two distinctly different sensory modalities perceived by different parts of the mouth and mediated by two separate sets of nerves and their central nuclei.

Red must color changes after crush.

Red must color changes after crush.

But back to color changes:

In the case of red wine, the color evolution is quite different: Immediately after being crushed, red wine starts out pale green-gray and pinks up over hours to days (depending on some variables).

To make a white sparkling wine (such as Champagne), the skins are removed at this point and only the juice is fermented. Additional steps are required, of course.

This sweet, soupy must (the mixture of juice, pulp, skins and seeds) slowly develops aromas and flavors along with color. It starts out vague, sometimes, grassy/weedy-smelling. With time, it increasingly resembles a fruit smoothie. You could probably compare it to several of the concoctions offered by Jamba Juice as it takes on color and flavor.

My reds (Aglianico and Montepulciano) tend to take on a crushed berry character before fermentation starts and then become grapey as the yeasts start (with the Montepulciano being more mixed berry-like and grapey, while the Aglianico expresses more plum and blueberry-like aromas) and finally end up with more varietal-speicific character after fermentation is done.

My Fiano started out very plain and grapey with honey-like notes. Think: frozen white grape juice concentrate. Having smelled a few white wines at crush, the general profile tends to be: white grape juice dominating hints of the varietal character of the finished wine. Once the yeasts kicked in, rich aromas not entirely different than what is found in the finished wine emerged. Over the course of the ferment, yeasty notes emerged and then waned. By the time the wine was dry, the aromatic profile shifted entirely to the varietal-specific end of the spectrum.

Occasionally, a wine may get stinky along the course of the primary fermentation. This may be inherent to the variety or the yeast strain and generally is quite transient as appears to be common with Syrah. Other times, it happens because the yeast is stressed due to low temperatures, or low (or otherwise disproportionate) nutrient levels. This is more troublesome as it may lead to a permanent, uncorrectable flaw.

Sometimes, the wine can become infected with a spoilage species like Acetobacter aceti. This can be prevented to a good extent by performing frequent punchdowns and by keeping the winery clean and free of insects.

One can blanket the cap with inert gases to stop A. aceti by depriving it of oxygen. It seems to have worked for me. Racking off the skins and pressing is another step to further reduce (if not eliminate) the impact of Acetobacter.

In the event that volatile acidity persists into the finished one, methods like reverse osmosis can be used. The obvious benefit is removal of VA, but I am not familiar with the risks and unwanted consequences.

Brettanomyces (proper name Dekkera bruxellensis) is another infection plaguing wines. It takes up residence in wood and affects wines aged in infected barrels. The problem with Brett is that one cannot stop it (although a new product claiming to do that has recently become available), control its impact or eliminate any “excess”. That is why it’s a flaw – no matter how a certain Maryland lawyer likes it.

While I’m talking about fermentative species, I cannot overlook the contribution made by yeasts (and to a lesser extent, malolactic bacteria). Yeasts are chosen for a number of characteristics: temperature tolerance, alcohol tolerance and even ability to affect tannins. But they are also chosen for the aromatic and flavor characteristics they impart on the finished wine – white or red. Yeasts affect the “flavor precursors” -molecules already present in the grapes and transform them into what we are more accustomed to finding in finished wines.

Jamie Goode does a good job of giving an overview of this in his video here (starting at marker 5′:45″).

There are also compounds, know collectively as “fermentation esters” which are more associated with individual yeast selections. These, however, dissipate rather quickly. Because they make a less lasting contribution to the character of a wine, they make a difference in wines consumed in the short-term.

The transformation of undetectable-to-the-human-senses aromatic and flavor precursors into detectable varietal hallmarks results in quite permanent sensory attributes of a wine. This, probably, is because those precursors are either more abundant in the must or their products are more stable in a finished wine than are fermentation esters. That does not mean that fermentation esters are not derived from some precursors in the grapes (or in oak, if a wine is barrel-fermented). Frankly, I do not know if they are.

It is this idea that aromatic and flavor precursors (along with acid and tannin levels) are: 1) coded for by the DNA of a specific clone or cultivar, 2) their production and expression is modulated (affected) by growing region as well as 3) growing practices and harvesting decisions that is at the core of identifying varietal and site typicity. In all fairness, not every grape produces wines as aromatically distinct as Gewürztraminer, or Pinor Noir (a clean one) or Cabernet Sauvignon, but the the less distinct varieties still do have a typical profile.

When one understands that whole concept, evaluating and rating wines based on preference and enjoyment becomes a null endeavor. The only method of objective and meaningful evaluation and rating wines, then, is one based on the 1) degree of fidelity of the wine to the aromatic and flavor components coded for by the DNA of the component grapes in a wine, and 2) the degree of complexity with which those are expressed while 3) avoiding flaws related to microbiological factors as well as problems originating during the remainder of the élevage such as oxidation, excessive use of additives, oak, etc.



Father, husband, physician, amateur guitarist, wine lover, wine writer, wine grower and wine maker trying to do it all within eye shot of downtown Los Angeles.
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One Response to Ch-Ch-Ch-Chaaangeeeees….

  1. Pingback: Good Reads Wednesday « Artisan Family of Wines

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