The height at which the water is poured can alter the extraction of the filtered coffee. A continuous and sufficiently high jet mixes the ground coffee better and allows you to obtain a more intense drink. Pouring hot water slowly from a kettle with a thin spout can create the ideal type of flow.
They are consumed every day billions of cups of coffee. From moka pots to espresso machines and filter coffee makers, there’s no shortage of ways to prepare your morning brew.
Each method has its followers and its rituals — including a specific grind, water temperature, pre-infusion time, and coffee-to-water ratio. Still, despite all the obsessive tinkering that surrounds coffee culture, most of us is guided more by habit than by science.
But scientists, who don’t know how to keep quiet, are always looking for a way to make good things even better — and we’ve already made it known in ZAP, for example.
Now, physicists have added another useful piece of information: a simple way to make coffee prepared by manual infusion stronger, richer and potentially less wasteful, says .
At the heart of the discovery is a seemingly simple trick: change shape how water is poured. More specifically, change the height from which it pours.
A team of scientists from the University of Pennsylvania demonstrated that, by Carefully manipulate water height and flow in manual infusion coffee, it is possible extract more from the same grains — or get a satisfying cup using a slightly smaller amount.
“What we recommend is to pour the water from as high a height as possible, still maintaining a laminar flow, in which the jet does not break up when it hits the ground coffee,” he said. Ernest Parkco-author of , which was published in Physics of Fluids.
The research team wanted to understand how to adjust just one variablein this case, the height from which water pourscould significantly alter what ends up in the cup.
The study started with an unusual challenge: how to look inside a cup of coffee without going blind because of its dark color.
To do this, researchers replaced ground coffee, opaqueby transparent particles of silica gel. These were placed inside a glass funnel, illuminated by a laser blade and recorded with a high-speed camera.
The images revealed something unexpected. When the hot water was poured from a sufficient height, and in a steady, continuous flow, it pierced the particle bed and triggered a kind of mini-slide.
The particles on the sides collapsed and fell toward the center, in a phenomenon the researchers called “avalanche” effect.
This avalanche is important because manual brewing coffee is, essentially, a extraction problem. The water has to reach the ground coffee, pass through it and transport the dissolved coffee compounds to the cup.
The greater the mixture, the greater the contact between water and ground coffee. And more contact means more extraction.
A simple way to get the right flow
Researchers discovered that pouring hot water slowly from a fine spout kettle can create the ideal type of flow. The long, narrow nozzle produces a concentrated jet, capable of falling from a greater height without falling apart immediately.
Esse jconcentrated act displaces the ground coffee and penetrates deeper on the coffee bed. Instead of just wetting the surface and flowing through the easiest channels, the water agitates the bed, faz recirculate the particles and exposes more coffee to fresh water.
As thin spout kettles They are already highly appreciated by many fans of manual infusion coffee. But even without one, the principle remains. The goal is to create a slow, narrow, steady flow. The essential thing is not the kettle itself, but the shape and stability of the falling water.
There is, however, an important caveate: pouring from a greater height does not automatically mean getting better coffee. The trick only works as long as the water remains in a smooth and continuous flow.
If the jet breaks down into drops, it loses the concentrated force that agitates the coffee bed. From that point on, lifting the kettle more can make extraction worseinstead of improving it.
The researchers found that, with this type of flow, it is possible to obtain a tasty drink even using less coffee.
The team recommends do experiments at home. You can start by using 10% less ground coffee — for example, 18 grams instead of the usual 20.
Afterwards, you should pour the hot water slowly and steadily from about 30 centimeters above the ground coffee. It is a controllable and safe height. The important thing is to always keep the jet intact.
Although the researchers don’t plan to continue studying coffee specifically, they say this type of physics applied to the kitchen can open new doors to science.
“We can actually learn something, both from a chemistry and a physics perspective, by looking at the kitchen,” he said. Arnold Mathijssenone of the study’s authors. “It takes us to new science where we didn’t expect to find it“.
