For better coffee, start with fewer beans
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The conventional coffee-brewing technique—grinding large amounts of beans as finely as possible—may actually deliver an inferior beverage, and waste grounds in the process. To provide a consistently high-quality drink, coffee producers should instead grind beans more coarsely and use fewer of them, according to a 2020 study published in Matter.
To calculate the transfer of mass from solid to liquid—that’s what happens when hot liquid combines with coffee grounds to create the signature beverage—scientists turned to battery modeling methodologies. They likened the movement of lithium ions through a battery’s electrodes to molecules like caffeine dissolving out of coffee grounds. Ultimately, the team chose to specifically analyze espresso-style coffee because the drink’s small size tends to magnify any brewing errors.
The researchers looked at various components of the brewing process, including dry coffee mass, water pressure, and the grounds’ coarseness. They found that fine grounds tend to clog espresso machines; ultimately, a stuffed coffee bed will stall the amount of liquid that can get extracted during the brewing process, and produce an uneven taste.
“Most people in the coffee industry are using fine-grind settings and lots of coffee beans to get a mix of bitterness and sour acidity that is unpredictable and irreproducible,” says co-senior author Christopher H. Hendon, a computational chemist at the University of Oregon. Though you’d expect finely ground beans to wet evenly within machines, some regions get more drenched than others; as a result, over-extracted areas produce bitter flavors and under-extracted ones add sourness. So with this method, it’s hard to get consistent espresso flavor and a high brewing ratio.
Meanwhile, coarse grounds are more efficient and yield more reproducible flavors. They require shorter espresso shot times–between 7 and 15 seconds–unlike the industry standard that falls between about 25 and 35 seconds. Longer shots further the dissolution of coffee compounds and thus carry a burnt essence, which is certainly not for everyone. Still, taste is undeniably subjective. The study does not claim to have mastered espresso flavors, but rather provides a starting point for more research.
Reference
Highlights
- Development of a model for extraction of espresso
- Experimental observation of inhomogeneous extraction
- Optimization of espresso parameters to minimize coffee waste
- Implementation to yield monetary savings in a cafe setting