Phenolic Compounds in Red and White Wines

In the world of enology, the distinction between white and red wines is more than just a matter of color—it is a complex interplay of chemistry, culture, and culinary art. Phenolic compounds stand at the forefront as the architects of these notable differences, significantly influencing attributes such as color and flavor, particularly in red wines. The importance of these substances is such that their study and understanding form a cornerstone for the scientific community in viticulture and viniculture, not only for their impact on the organoleptic characteristics of wines but also for their potential health benefits.

Derived from various parts of the grape bunch, phenolic compounds range from carboxylic acids to flavonoids, anthocyanins, and tannins, all of which are extracted during the vinification process. As wine ages, the chemical structure of these compounds transforms, depending on storage conditions—a phenomenon that continues to be a focus of research to decode the complex processes governing these transformations.

Focusing on phenolic acids, we find that these colorless molecules are predominantly present in red wines. Their presence, tenfold greater in reds than in whites, does not contribute specific aroma or flavor to the wine; however, they play a significant role in the chromatic evolution of wine, potentially contributing to the yellowish hue of older red wines if oxidation occurs. In situations where wine contamination occurs, these acids can turn into volatile phenols, resulting in undesirable aromas reminiscent of leather or a barnyard, a topic that will be detailed when addressing wine faults.

Flavonoids, on the other hand, display a range of yellow hues, with flavonols leading the charge. These compounds are responsible for the intense yellow pigment in both white and red grapes. They do more than provide color; they also act as antioxidants, playing a role in preventing cardiovascular diseases, resonating with the phenomenon known as the French paradox. White wines, fermented without contact with grape skins and seeds—where these flavonoids reside—have a lower concentration of these compounds.

Anthocyanins are perhaps the most studied phenolic compounds in enology, responsible for the reddish hues of wine. Predominantly located in the grape skin and, in some teinturier varieties, in the pulp, these pigments are essential for the characteristic color of red wine. Malvidin emerges as the dominant molecule in most red grape varieties, decisively influencing the wine's hue. However, the proportion of other anthocyanins varies among different grape varieties, thus defining their distinctive characteristics.

The hue of anthocyanins is subject to the conditions of the environment in which they are found; pH and the presence of other phenolic compounds and flavonoids can shift their color toward more bluish tones. The concentration of anthocyanins is subject to significant variations depending on the grape variety and the age of the wine. For instance, while a Pinot Noir may exhibit around 100 milligrams per liter, a Cabernet Sauvignon or a Tempranillo can contain up to 1500 milligrams per liter. However, during the aging of the wine, the concentration of anthocyanins decreases dramatically, potentially reaching a minimum of up to 50 milligrams per liter. To maintain a stable color over time, anthocyanins associate with tannins, forming complex but enduring structures.

A special mention is necessary for tannins, which warrant an entire article to themselves—for which we recommend visiting some of the numerous articles dedicated to this compound here at Vinetur.

This broad spectrum of phenolic compounds not only endows wine with its unique sensory properties but also contributes to its nutritional value and its role in gastronomic culture. Their study and understanding not only enrich the appreciation of wine but also pave the way for a more refined and health-conscious viniculture.

As we explore these compounds further, we delve into the intricate relationship between science and sensory experience, where each sip of wine is a testament to the delicate balance of nature's offerings and human craftsmanship. The journey of a grape from vine to wine is a narrative of transformation, where the land, the climate, and the vintner's touch converge to create a beverage that is celebrated the world over for its depth, complexity, and ability to bring people together over a shared table. In a world increasingly focused on wellness, the role of phenolic compounds in wine provides a fascinating intersection between pleasure and health, tradition and science, offering a kaleidoscopic view into the beverage that has captivated humanity for millennia.