How to make the perfect cup of coffee, according to science

Make a great homemade brew every time with this top tip

Scientists have cracked the secret behind what coffee drinkers around the world have wanted to know for years – how to make the perfect cup.

Mathematicians and physicists have come together to devise a formula for making a flawless brew as part of a study which has been published in the journal Matter.

Dr Jamie Foster, a mathematician from the University of Portsmouth, launched the study after finding that sometimes two shots of espresso, made in seemingly the same way, can taste different.

Foster’s team created a mathematical theory to describe extraction from a single grain, many millions of which comprise the coffee “bed” which you would find in the basket of an espresso machine.

“The conventional wisdom is that if you want a stronger cup of coffee, you should grind your coffee finer,” Foster said.

"This makes sense because the finer the grounds mean that more surface area of coffee bean is exposed to water, which should mean a stronger coffee."

However, the researchers found that coffee became more "reliable" from cup to cup when using fewer beans which had been ground more coarsely.

"When beans were ground finely, the particles were so small that in some regions of the bed they clogged up the space where the water should be flowing,” Foster explained.

“These clogged sections of the bed are wasted because the water cannot flow through them and access that tasty coffee that you want in your cup.”

Instead, the mathematician stated that fewer beans which are ground more coarsely results in a “more efficient extraction”.

He added that this method is also cheaper, because it uses fewer beans and is also kinder to the environment.

"Once we found a way to make shots efficiently, we realised that as well as making coffee shots that stayed reliably the same, we were using less coffee,” Foster added.

According to a spokesperson from the University of Portsmouth, the new recipe has been trialled in a small coffee shop in the United States.

Over a period of one year, the coffee shop has reported saving thousands of dollars.

“Estimates indicate that scaling this up to encompass the whole US coffee market could save over 1.1 billion US dollars (£843 million) per year,” said the spokesperson.

It is reportedly the first study to use theoretical modelling to study the science of the perfect espresso.

Last year, a separate study conducted by researchers from Florida Atlantic University and Harvard Medical School found that drinking coffee just before bed does not affect quality of sleep.

The team monitored 785 people for a total of 5,164 days and nights, recording how much caffeine, alcohol and nicotine they consumed as well as sleep duration, sleep efficiency and how quickly participants woke up after drifting off.

The study found that while nicotine and alcohol did disrupt sleep – with a pre-bed cigarette taking 42 minutes off total duration of sleep for insomniacs (a person who is regularly unable to sleep) – caffeine seemed to have no effect.