Decoded: What sugar does to your coffee

The sugar in your cup of coffee not only gives a sweet taste but also helps reduce the bitterness of tea and coffee, new research reveals.

Scientists from the University of York have provided new insights into the way in which caffeine, sugar and water interact at the molecular level to affect the taste of hot beverages.

Appreciated for its "reviving" stimulant effect, caffeine is, however, also in part responsible for the bitter taste in tea and coffee.

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 Seishi Shimizu from the university's department of chemistry found 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 explained.

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.

"Encouraged by this discovery, we are working hard to reveal more about the molecular basis of food and cooking," Shimizu added in a paper published in the journal Food and Function.