I was drinking coffee the other day and noticed that I don’t like drinking HOT coffee. I enjoy drinking coffee around 120°F. Coffee is brewed around 200°F and typically served between 180°F-190°F.

It got me thinking about why we drink coffee hot and how does temperature affect our perceived taste¹.

After doing some research I found an article about Yale scientist Barry G. Green regarding Thermal Taste:

“We’ve discovered that specific tastes can be produced by temperature stimulation, just as certain chemicals can evoke only certain taste qualities,” 

Green and his colleagues call this temperature stimulation of taste “thermal taste.” It has been known since the first electrical recordings of taste nerves that they are sensitive to temperature as well as to chemicals, but it was not known how the brain interprets this thermal stimulation. Thermal taste shows that it is interpreted as taste, not temperature, say the researchers.

The close relationship between temperature and taste qualities suggests receptors in the tongue that respond to chemicals have certain properties that make them vulnerable to specific kinds of temperature change, explain the scientists. This information may provide clues to understanding the nature of these receptor processes.

Thermal taste is different on different parts of the tongue, explains Green, indicating that taste receptors that are sensitive to temperature are not uniformly distributed throughout the tongue. For example, sweetness is more readily perceived on the tip, sourness on the side and bitterness in the back, he says.

Not everyone experiences thermal taste, notes Green. About two out of every three people tested in the study experienced at least one taste quality — sweetness is the most common thermal taste and saltiness is the least common. Green notes that these individual differences are consistent with other evidence that taste physiology and taste experiences vary substantially from person to person.

“Thermal taste probably does not affect the taste of most foods and beverages because the temperature conditions that produce it are rarely encountered during eating or drinking, and when they are, the chemical tastes of foods and beverages tend to mask thermal tastes,” Green says. “However, it is possible that frozen desserts may taste somewhat different to individuals sensitive to cold-induced sensations of thermal sourness and saltiness.”

Individuals sensitive to salt will notice that an ice cube touched to the very tip of the tongue for a few seconds will begin to taste salty, explains Green. Unfortunately, he adds, saltiness is the least common of the thermal tastes, and this is not a reliable way to demonstrate the phenomenon.

A little more research and I found an article on Nature.com about Ion channels in our tongues:

TRPM5, a cation channel of the TRP superfamily, is highly expressed in taste buds of the tongue, where it has a key role in the perception of sweet, umami and bitter tastes. Activation of TRPM5 occurs downstream of the activation of G-protein-coupled taste receptors and is proposed to generate a depolarizing potential in the taste receptor cells. Factors that modulate TRPM5 activity are therefore expected to influence taste. Here we show that TRPM5 is a highly temperature-sensitive, heat-activated channel: inward TRPM5 currents increase steeply at temperatures between 15 and 35 °C. TRPM4, a close homologue of TRPM5, shows similar temperature sensitivity. Heat activation is due to a temperature-dependent shift of the activation curve, in analogy to other thermosensitive TRP channels. Moreover, we show that increasing temperature between 15 and 35 °C markedly enhances the gustatory nerve response to sweet compounds in wild-type but not in Trpm5 knockout mice. The strong temperature sensitivity of TRPM5 may underlie known effects of temperature on perceived taste in humans, including enhanced sweetness perception at high temperatures and ‘thermal taste’, the phenomenon whereby heating or cooling of the tongue evoke sensations of taste in the absence of tastants.

Why do we drink coffee hot? Does it scientifically taste better at lower temperatures? How does temperature affect eating other foods? 

While yes it is necessary to brew coffee at those high temperatures, to extract the necessary oils and solubles, why do we drink it that hot? During cuppings we often taste coffee many times over the temperature range and almost unanimously agree that coffees change and “open up” as they cool, becoming sweeter and more complex. 

How does temperature affect our perceived taste and should we change the temperature at which we serve coffee?   

Footnotes 
1. Our perceived taste is built on combining different elements such as:  chemical taste, smell, texture, and temperature.