In order to understand the chemistry of wine, you must first understand that the basic building block for much of wine chemistry centers on the organic molecule called a “phenol.”  In chemistry terms, “phenols” are a circular molecule of carbon and oxygen.  That said, think of phenols as the basic building block upon which other phenol molecules (poly phenols) or other organic molecules are added to make larger molecules.  Each one of these larger molecules interacts with other (organic and inorganic) molecules to produce other molecules to include acids, esters, aldehydes, and a whole range of the chemicals that make wine what is it.  You can think of these molecules as the chemical components that make up wine.  Remember, 80% of wine is hydrogen and oxygen molecules combined:  H2O.

Tannins are astringent, bitter plant polyphenols that either break up or shrink proteins.  The key words being “bitter,” “plant,” “polyphenols” that attack proteins.  Our mouths are full of protein, so when you put a bitter, polyphenol, from a plant in your mouth, a chemical reaction takes place and the astringency from the tannins causes the dry and puckery feeling in the mouth.