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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Extracting the best flavor from coffee    
      
     Date:   
         May 9, 2023   
     Source:   
         American Institute of Physics   
     Summary:   
         Researchers explore the role of uneven coffee extraction using   
         a simple mathematical model. They split the coffee into two   
         regions to examine whether uneven flow does in fact make weaker   
         espresso. One of the regions in the model system hosted more   
         tightly packed coffee than the other, which caused an initial   
         disparity in flow resistance. The extraction of coffee decreased   
         the flow resistance further. Understanding the origin of uneven   
         extraction and avoiding or preventing it could enable better brews   
         and substantial financial savings by using coffee more efficiently.   
      
      
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   FULL STORY   
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   Espresso coffee is brewed by first grinding roasted coffee beans into   
   grains.   
      
   Hot water then forces its way through a bed of coffee grains at high   
   pressure, and the soluble content of the coffee grains dissolves into   
   the water (extraction) to produce espresso.   
      
   In 2020, researchers found that more finely ground coffee beans brew a   
   weaker espresso. This counterintuitive experimental result makes sense if,   
   for some reason, regions exist within the coffee bed where less or even   
   no coffee is extracted. This uneven extraction becomes more pronounced   
   when coffee is ground more finely.   
      
   In Physics of Fluids, from AIP Publishing, University of Huddersfield   
   researchers explored the role of uneven coffee extraction using a simple   
   mathematical model. They split the coffee into two regions to examine   
   whether uneven flow does in fact make weaker espresso.   
      
   One of the regions in the model system hosted more tightly packed coffee   
   than the other, which caused an initial disparity in flow resistance   
   because 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.   
      
   "Our model shows that flow and extraction widened the initial disparity   
   in flow between the two regions due to a positive feedback loop, in which   
   more flow leads to more extraction, which in turn reduces resistance and   
   leads to more flow," said co-author William Lee. "This effect appears   
   to always be active, and it isn't until one of the regions has all of   
   its soluble coffee extracted that we see the experimentally observed   
   decrease in extraction with decreasing grind size."  The researchers   
   were surprised to find the model always predicts uneven flow across   
   different parts of the coffee bed.   
      
   "This is important because the taste of the coffee depends on the level   
   of extraction," said Lee. "Too little extraction and the taste of the   
   coffee is what experts call 'underdeveloped,' or as I describe it: smoky   
   water. Too much extraction and the coffee tastes very bitter. These   
   results suggest that even if it looks like the overall extraction is   
   at the right level, it might be due to a mixture of underdeveloped and   
   bitter coffee."  Understanding the origin of uneven extraction and   
   avoiding or preventing it could enable better brews and substantial   
   financial savings by using coffee more efficiently.   
      
   "Our next step is to make the model more realistic to see if we can obtain   
   more detailed insights into this confusing phenomenon," said Lee. "Once   
   this is achieved, we can start to think about whether it is possible to   
   make changes to the way espresso coffee is brewed to reduce the amount   
   of uneven extraction."   
       * RELATED_TOPICS   
             o Health_&_Medicine   
                   # Staying_Healthy # Diseases_and_Conditions   
             o Matter_&_Energy   
                   # Nature_of_Water # Nuclear_Energy   
             o Computers_&_Math   
                   # Computer_Modeling # Mathematical_Modeling # Mathematics   
       * RELATED_TERMS   
             o Coffee o Caffeine o Constructal_theory o Turbulence   
             o Aerodynamics o Viscosity o Extraction_(dental) o   
             Psychoactive_drug   
      
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   Story Source: Materials provided by American_Institute_of_Physics. Note:   
   Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. William Lee, Ann Smith, Arsalaan Arshad. Uneven Extraction in Coffee   
         Brewing. Physics of Fluids, 2023; DOI: 10.1063/5.0138998   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230509122007.htm   
      
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