The science behind the perfect cup of coffee

Coffee lovers, rejoice! Scientists have unlocked the key to consistently tasty espresso. Researchers at the University of Oregon in the US focussed on the process of grinding coffee beans and the brewing method for the research.

“One day you might have a good cup of coffee and the next day you might not. From a scientific perspective, it has always puzzled me why we could not do the same thing twice,” said Christopher H Hendon from the University.

He added, “There is a point in grinding coffee beans when you make too many small particles, which stick together and result in reduced extractions.” Although smaller particles mean a greater surface area, which should result in consistently tasty espresso, there is a critical point at which smaller is not better, researchers said. For this reason, the grinders used can have a significant impact on the flavour of the resulting cup of coffee.

Additionally, when extracting the espresso, the water should come into contact with the coffee grounds uniformly, according to the research presented at National Meeting & Exposition of the American Chemical Society (ACS) in the US. Passing water through the ground coffee beans in a systematic manner would ensure that all particles come in contact with water equally.

In comparison, with a traditional drip-brew coffee pot, the water drips mainly through the centre of the grounds while the grounds on the outside have little contact with water.

By collaborating with Baristas, Hendon developed a method by which they can achieve their desired flavour profile consistently. Hendon proposes an optimisation process achieved by altering grinding size and brew ratio. “By predetermining the coffee-towater ratio, as well as the water pressure, the maximum extraction can be systematically determined,” he said.

“The Baristas can then iteratively improve their espresso reproducibility, while reducing waste coffee mass,” said Hendon.

Previous research in his lab explored several variables that impact the reproducibility of espresso. For example, water hardness can affect flavour. The freshness of the coffee beans can also impact how tasty a cup of coffee is.

PHOTO: SHUTTERSTOCK The size of the particles of ground coffee might alter the taste, suggests a study