What’s in the 2%?

Mis à jour : 10 janv. 2019

We recently talked with Anouck Champsaur, PhD at Columbia University; she shared with us her scientific knowledge on wine, another way to look at the product. Here is what we have learned.

The price of a bottle of wine can range from a few dollars to hundreds of thousands. It is fascinating to understand where the discrepancy in value and flavor arises in this seemingly simple substance prepared from the fermentation of grape juice. All wine is composed, roughly, of 85% water (H2O) and 13% ethanol (CH3CH2OH). So, what’s in the remaining 2%, and how did it get there?

Basic structure of a pigment of Anthocyans: The flavio-cation.

The remaining 2% of wine consists of molecules such as acids, sugars, aroma compounds, pigment compounds, tannins, and flavor compounds. In reality, complex biological and chemical processes dictate the identity and distribution of such molecules in wine, and these processes begin as early as in the soil in which the vine grows. Various elements like the soil, weather conditions, water supply, and temperature affect the grape while it is still attached to the vine, and alter, for example, its moisture levels, nutrients, and sugar content. Then, the grapes are harvested and pressed with or without the stems, and the juice begins the fermentation process. Sulfur dioxide (SO2) is often added at this stage to inhibit wild yeasts and bacteria, and prevent oxidation. Fermentation is the process by which sugars (C6H12O6; naturally occurring in the juice and sometimes added) are converted to ethanol (CH3CH2OH) and carbon dioxide (CO2). This process is carried out by yeast, a single cell living organism that is either naturally occurring in the grape/cellars or often added. The acid levels and temperature play a critical role in the fermentation process and also affect the bacteria, naturally present in grape juice, and their own biochemical reactions that yield additional flavor compounds like fatty acids and esters.

Lastly, there is a mystical ingredient: time. The aging process of a wine consists of chemical reactions that alter its flavors and textures over months and years. Altogether, these biological and chemical processes are multilayered and complex. However, tools are available that allow us to identify, separate, characterize, and quantify all of the different molecules present in a bottle of wine.

For example, when one wishes to analyze the molecules present in a bottle of wine, the first step is to separate the components of interest from water. The great majority of these molecules are organic molecules (molecules with a carbon backbone) that aren’t happily dissolved in water – same reason oil doesn’t mix with vinegar. However, the ethanol present in the wine helps to bring these organic molecules into the solution. This is because ethanol has two parts: one that “likes” water (-OH), and one that doesn’t (CH3CH2-). It serves as the liaison between water and the organic molecules. The organic molecules are extracted with another organic solvent such as dichloromethane, CH2Cl2, or ether, (CH3CH2)2O. They are subsequently analyzed and separated with highly sensitive chromatography instruments that detect and separate parts-per-million amounts.

ISVV, Institut des Sciences de la Vigne et du Vin in Bordeaux.

Entire academic departments and research centers all over the world are dedicated to this rigorous chemical analysis of wine (e.g. the Viticulture and Enology Department at UC Davis, or ISVV, Institut des Sciences de la Vigne et du Vin in Bordeaux). While many of the processes themselves remain mysterious or poorly understood, chemists and their instruments have become quite good at analyzing the components in the final product. Knowing the final distribution of molecules in many different kinds of wine bottles allows scientists to develop patterns and assign precise molecules as the chemical stamps of a particular flavor, mouthfeel, or aroma, which are still subjectively characterized as “oaky”, “full-bodied”, and so on. The flavor wheels can then become less subjective, and our appreciation of wine can deepen and be substantiated with true, concrete data.

But, if wine is just molecules added to a mixture of water and ethanol, why haven’t we been able to reconstruct it ourselves? Certain people have had this idea, like the folks from Ava Winery (recently rebranded as Endless West, https://endlesswest.com/). It turns out, it is extremely complex to produce a synthetic wine.

While the scientific approach deepens our understanding of taste, certain mysteries remain. Vinifyed can help consumers hone their individual preferences within the vast jungle of the wine world and concretize the subjective with other forms of data: numbers and statistics.

The Vinifyed Post.

#enology #wine #vinifyed #ColumbiaUniversity #winescience

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