Illustration of a bottle of wine.Most wines are 98 percent water and ethanol, says Biotechnology Professor Edward Bozzi ’68 of URI’s Alan Shawn Feinstein College of Education and Professional Studies, so it’s the other 2 percent that distinguishes one wine from another—and a great wine from an average one.

So what’s in that 2 percent?

Half is glycerol, says Bozzi; it changes wine’s viscosity. When you see “legs” or “tears” on your glass after swirling the wine, it’s thanks to glycerol, and there’s a name for it: the Marangoni effect.

Wine is somewhat acidic, so there’s tartaric acid in the mix, at around 0.5 percent. Then there are carbohydrates; sweeter wines contain more fructose and glucose than the dry ones, but we’re still talking around half a percent.

Finally, at just 0.1 percent, it’s the phenolics that make wine special. Flavonoids and anthocyanins, in varying proportions, give wines distinctive colors and tastes. Phenolic tannins give you a feeling of dryness.

“Now that you know a little more about wine’s chemistry,” says Bozzi, “perhaps your next glass will taste even better.”