Getting the Best Flavor from Coffee to make Espresso
Espresso coffee is a popular beverage brewed by grinding roasted coffee beans into grains and then forcing hot water at high pressure through a bed of coffee grains to dissolve the soluble content of the coffee and produce espresso. However, recent research has found that more finely ground coffee beans make weaker espresso, which is a counterintuitive result.
This phenomenon is due to regions within the coffee bed where less or no coffee is extracted, and this uneven extraction is more noticeable when coffee is ground more finely. To investigate the role of uneven coffee extraction, researchers from the University of Huddersfield conducted a study published in the Physics of Fluids journal.
They split the coffee bed into two regions to examine if uneven flow results in weaker espresso. They found that one of the regions had more tightly packed coffee than the other, causing an initial disparity in flow resistance because the water flows more quickly through more tightly packed grains. The extraction of coffee decreased the flow resistance further, as coffee grains lose about 20% to 25% of their mass during the process.
Researchers’ observation of coffee extraction flow
The researchers observed that flow and extraction widened the initial disparity in flow between the two regions, leading to a positive feedback loop, in which more flow led to more extraction, which reduced resistance and led to more flow. They also found that uneven flow across different parts of the coffee bed always occurred, which is essential as the taste of the coffee depends on the level of extraction.
Too little extraction results in underdeveloped coffee, which tastes like smoky water, while too much extraction makes the coffee taste very bitter. Therefore, understanding the origin of uneven extraction and avoiding or preventing it could lead to better brews and substantial financial savings by using coffee more efficiently.
The researchers’ next step is to make the model more realistic to gain more detailed insights into this phenomenon and consider changes to how espresso coffee is brewed to reduce the amount of uneven extraction.
Read the original article on PHYS.
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