Stronger pour over coffee with slow steady pouring revealed by scientists

Researchers have uncovered an effective method to enhance the flavour of pour-over coffee without the need for more beans or expensive filters. By pouring water slowly, steadily, and from a notable height, coffee enthusiasts can significantly improve the strength of their brew.

Pour-over coffee has become a daily ritual for many, yet it often lacks the desired potency. The findings from a team at the University of Pennsylvania, led by Dr Arnold Mathijssen, shed light on the optimal pouring technique. Pouring water carefully increases the time it spends in contact with coffee grounds, facilitating better extraction while elevating the pouring height promotes thorough mixing.

The researchers conducted a series of experiments using transparent silica gel particles that represented coffee grounds, illuminated with lasers and recorded by high-speed cameras. Their results demonstrated that a slow pour maximises contact time. However, when pouring from insufficient heights, the water’s velocity was too low to penetrate and agitate the bed of particles effectively. In contrast, pouring from a higher position created the necessary agitation but must be executed consistently, maintaining an unbroken water jet.

This unbroken jet effect allows the water to dig into the coffee grounds, prompting a cascade-like motion, akin to an avalanche, which further enhances the mixing process. Dr Mathijssen explained, “The increased height compensates for the slow pouring, and you only achieve the desired avalanche effect when sufficient energy is present.” Thus, a sweet spot is found between speed and height for the perfect pour.

For those seeking to experiment at home, a practical suggestion is to reduce the quantity of ground coffee by ten percent, for example, from 20 to 18 grams per cup. This reduction could lead to a more refined tasting experience, with the added benefit of using fewer resources.

Experts outside of the study, like Professor Jamie Foster from Portsmouth University, support the validity of these findings, suggesting that similar principles might apply to other coffee brewing methods. This opens avenues for innovative brewing practices that could address challenges posed by climate change on coffee production.