Why does coffee, tea or wine taste better in a high-fired unglazed cup than in glass?

Nucleation: Adding additional molecules of oxygen created by the texture of LaughinGnome Pottery clay!

A cup of tea or wine contains many flavor and aroma compounds including phenols, amino acids, and minerals. In a high-fired unglazed ceramic cup, the inside of the cup has a rougher surface than the inside of a glass or glazed ceramic cup, and this roughness can break up these flavor compounds into smaller bits.

Think of cooking with garlic. If you throw a whole garlic clove into a dish you’re cooking, you’ll get a certain amount of garlic flavor. If you mince that same garlic clove into little pieces, and add that to the dish, you’ll get more garlic flavor because there is more surface area for the garlic to interact with oxygen, with other components in the food, and with your nose and mouth.

In the same way, the rough surface of the unglazed cup brings out the flavor and aroma compounds of tea and wine so they are more available to our taste and smell.

This effect is related to the physical process of “nucleation.” When you pour champagne into a glass, you see that the bubbles originate at certain places in the glass, and rise to the surface. The places where the bubbles arise are imperfections in the smooth surface of the glass. They’re called “nucleation sites,” because that’s where the dissolved gas in the champagne nucleates into bubbles. The same thing happens with beer (where the bubbles form the head) and carbonated beverages. We think that on a more subtle scale this is also going on with tea. Though you can’t see or taste bubbles in tea (unless you’re drinking bubble tea), the flavor compounds in the tea are nucleating at these rough sites on the inner microscopic surface of the cup. This contributes to the oxidation of flavor compounds, which releases flavor. According to one reference, oxidation of phenols can contribute fruity and nutty aspects to the taste of wine. Something similar is going on with tea and other beverages.

To see this nucleation process at work, we did an experiment. We poured carbonated water into a wine glass, and the same amount of carbonated water into a high-fired unglazed teacup.
In the wine glass, the water bubbled moderately. 

In contrast, pouring the carbonated water into the unglazed cup caused a violent eruption of bubbles, indicating that oxidation was happening much faster.