What are phenols?

Phenols are aromatic alcohols, which means that they are molecules that consist of a six-carbon aromatic ring with a hydroxyl (OH) group attached to one of the ring carbons. To an organic chemist, “aromatic” means that the ring includes an unpaired electron that is shared among all of the carbon atoms of the ring and. Electrons are like people: they like to be paired, are a little unstable when single, and tend to react with other molecules in search of a partner.

The most basic phenol is represented as

 More complex members of the phenol family are distinguished by having other things attached to one or more of the other ring carbons.

Because phenols have a free-floating (“delocalized”) electron, they form very strong hydrogen bonds with each other and other compounds with an unpaired electron. Non-covalent bonds – the bonds that form in-between molecules, including hydrogen bonds – help govern melting and boiling points: the stronger and more numerous the non-covalent bonds, the more energy input it takes to break them. When non-covalent bonds break, molecules move around more and move further from each other, resulting first in the melting of a solid and then, when the input of even more energy causes even more movement, in the boiling of a liquid.

ERGO: phenols have very high melting and boiling points. ERGO: phenols are solids at room temperature. ERGO: phenols, including the colorful ones that make red wine red and the flavorful ones that add depth and character to wine exist in wine as suspended particles. ERGO: they can be removed by filtering. ERGO: enough filtration can cause a wine to lose color, flavor, and mouth-feel (in part) because phenols are lost in the filtration process.

There are three major categories of wine-related phenols: p-hydroxybenzoic acids, cinnamic acids, and flavanoids. What do they do for wine? Phenols are responsible for a major part of the color and flavor of wine. They are, In fact, so important in so many ways that I’ll save more details for another post devoted solely to the topic.

For now, back to Fenema’s Food Chemistry!


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