Why does coffee taste bitter?

Most people think that the bitter taste in coffee comes from caffeine, right? Think again.

A recent study has detailed why caffeine is not the sole contributor to the bitter taste of coffee.

The Leibniz-Institute for Food Systems Biology and the Technical University of Munich (TUM) explained in a recent paper that the molecular interactions between bitter substances and bitter receptors is more complex than once thought.

How is coffee bitter?

The Munich based scientists used cell-based testing system – a type of artificial tongue – to guage bitterness and analyse substances.

Then, the team investigated five different bitter coffee constituents:

• Mozambioside (found in green coffee)
• Bengalensol (found in roast coffee)
• Cafestol (coffee compounds)
• Kahweol

How did they analyse the compounds?

Based on the results of their study, the research team assumes that mainly two of the 25 human bitter taste receptors respond to the coffee’s constituents.

What were the results of the coffee bitterness test?

The caffeine concentration required to activate the bitter taste receptor to the same degree as mozambioside or bengalensol was about 30 and 300 times higher.

Further studies suggest that the bitter substances contained in coffee interact with each other.

These studies showed that kahweol and mozambioside exhibit similar binding properties for the bitter taste receptor as caffeine.

Compared to mozambioside, however, kahweol receptor activation was relatively weak and, depending on the dose, was capable of inhibiting the mozambioside-induced activation of the bitter taste receptor.