The real reason we put sugar in coffee

Caffeine, sugar, and water interact at the molecular level to affect the taste of hot beverages. (Credit: Steven Feather/Flickr)

A sweet tooth isn’t the only reason we put a little sugar in coffee or tea. Scientists say sugar has an important effect in reducing bitterness, not just by masking it but by influencing the fundamental chemistry.

The research published in the journal Food and Function reveals new insights into the way in which caffeine, sugar, and water interact at the molecular level to affect the taste of hot beverages.

Caffeine is in part responsible for the bitter taste. The caffeine molecules tend to stick to each other when in water, and this tendency is further enhanced by the addition of sugar. For many decades, scientists have assumed that this was due to the strengthening of bonds between water molecules around the sugar.

But research led by Seishi Shimizu of the York Structural Biology Laboratory at the University of York instead suggests that the underlying cause is the affinity between sugar molecules and water, which in turn makes the caffeine molecules stick together (or aggregate) in order to avoid the sugar.


This is why we experience less of their bitter taste. Proper understanding of the fundamental rationale behind this process may assist food scientists in many ways.

He used statistical thermodynamics—a branch of theoretical physical chemistry linking the microscopic realm with the everyday world—to investigate the molecular-level activities and interactions behind our daily food and drink.

“It is delightful indeed that food and drink questions can be solved using theory, with equipment no more complex than a pen and paper,” says Shimizu.

Source: University of York