It's estimated that wine has over 1,000 aromatic components, half of which are produced by yeast during alcoholic fermentation. Some aromas seem to naturally escape from the wine, while others can only be perceived if we enhance them by
swirling the glass, which indicates their different volatility. Over time, some of these components combine with others to form heavier molecules that become insoluble, resulting in tannic sediments or tartrate crystals.
Apart from water, the most important component of any wine is ethyl alcohol or ethanol, mainly produced by Saccharomyces yeast during fermentation. Although ethanol doesn't have much flavor, it gives body and density to the wine and alters our perception of other components. For example, a wine with a moderate alcohol level may give the impression of being more flavorful th
an a similar wine with a higher alcohol level, while excessively high alcohol content can overshadow fruity character and other aromas. Alcohol should be balanced with the other components of the wine to be perceived as integrated.
Next, we have organic acids. Grapes contain malic and tartaric acid, as well as a small amount of citric acid. Tartaric acid stabilizes the finished wine, but a portion of it can precipitate in the form of tartrate crystals resembling small pieces of glass. Malic acid, named after its presence i
n apples (malus in Latin) and its characteristic flavor, is transformed into lactic acid through a reaction known as malolactic fermentation.
This process can occur spontaneously, but it is usually inoculated with lactic bacteria from the Oenococcus oeni family. Lactic acid is softer and juicier than malic acid, giving the wine a rounder character and greater texture. In some white wines made from more fruity and floral varietals, lactic fermentation is inhibited to maintain a more acidic and sharp profile. Other acids present in wine include succinic acid, a byproduct of fermentation, acetic acid, and butyric acid. High levels of acetic acid, which smells like vinegar, and butyric acid, which smells like sour milk or rancid butter, are considered wine defects caused by bacteria. In addition to preserving the wine, acids contribute to freshness, depth, and contrast, balancing alcohol, residual sugar, and aromatic components, as well as aiding in the dissolution of fat from food when consumed with wine. A wine lacking acidity, with high pH, will appear dull, flat, and lacking interest.
Maturity:
Grapes contain almost the same amount of glucose and fructose, which are transformed into alcohol during fermentation. Occasionally, winemaking stops this process to leave certain amounts of what we call residual sugar. During alcoholic fermentation, yeast prefer glucose, so most of this residual sugar is composed of the sweeter fructose. Dry wines have a residual sugar level below 4 g/liter, making it usually undetectable except for its indirect effects of reducing acidity or slightly increasing body. At the other end of the spectrum, some wines may contain over 100 g/liter of residual sugar. The sweetness of a wine can be masked by acidity and, to a lesser extent, tannins.
Polyphenols are composed of a wide group of chemical elements found mainly in grape skins. They are responsible for much of the wine's flavor and, over time, interact with other elements to form a wide range of secondary and tertiary aro
ma components. Anthocyanins are a class of red, blue, and purple polyphenols extracted from red wine through contact with the grape skins during alcoholic fermentation.
They are unstable and, in the presence of oxygen, react with tannin molecules to form longer chains that precipitate, resulting in the wine losing color. At the same time, these anthocyanins act as antioxidants that help preserve the wine and, according to some scientists, benefit the consumers as well. Tannins are a group of polymerized polyphenols found in grape skins, seeds, and stems. The tannins in wine are related, among other things, to the duration of contact with the skins and other solid matter. While tannins are primarily associated with red wines, some white wines have a certain amount of skin contact, giving them a slightly astringent texture. Oak barrels can also provide additional tannins for both white and red wines. Tannins can be detected as a textural or structural element, along with a certain astringency and bitterness. They interact with saliva proteins to form more complex components that inhibit lubrication, resulting in a sensation of dryness and roughness in the mouth. With aging in the bottle, tannins transform into softer and smoother textures, occasionally appearing gentle and silky. The exact process by which this occurs is still not fully understood.
The aroma and most flavors of a wine are perceived not on the tongue but through the nose, triggered by volatile components that escape from the liquid's surface and reach the olfactory bulb. These volatile components originate from both the grape itself and chemical reactions, in the form of byproducts, during fermentation and subsequent aging. They include heavy alcohols, esters, aldehydes, lactones, and pyrazines. Short-chain esters are responsible for fruity and floral notes, while long-chain esters contribute to perfumed and soapy notes. Aldehydes facilitate nutty flavors, hints of sherry, and oxidation notes, while pyrazines provide vegetal, herbaceous, and green pepper aromas.
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