Advanced Coffee Making

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Brewed Coffee

ACM 5.06 – Recap and Glossary

Chapter 5 Recap

  • The concentration gradient between the liquid in the grinds and the rest of the slurry is theoretically higher in drip coffee than immersion coffee by the end of the brew cycle.

    • This can make drip coffee more difficult to hit the precise extraction yield target.

  • Drip coffee is usually much more transparent than immersion brews because of the sedimentary filter bed.

    • Coffee bed depth is an important variable to monitor and as a rule, the deeper the bed, the coarser you will need to grind.

  • The liquid retained in the coffee grinds has traditionally been considered so dilute, we can round it down to zero.

    • It is clear this needs to be reexamined and that the interstitial liquid in a brew contains a non-zero amount of extracted mass.

    • To improve the accuracy of extraction measurements, we are researching better ways to measure the strength of the interstitial liquid.

New Words

  • Capillary Action: the ability of a liquid to flow in narrow spaces against the force of gravity.

  • Darcy’s Law: an equation developed by Henry Darcy which describes the flow of water through a porous medium. It suggests there is an inverse relationship between the thickness of a bed and the flow rate of the liquid.

  • Drip Coffee: a drip coffee is any gravity fed brew method that involves the erosion of solids through some kind of strainer/filter.

  • Immersion Brew: any brew method which hits its maximum dilution level at the beginning of the brewing process — usually with grinds fully immersed in water.

  • Interstitial Liquid: the liquid in a slurry that occupies the space between coffee grinds and in porous media like coffee grinds, inside the grinds too.

  • Maximum Dilution: the point in the brewing process when all the brew water has been added to the brew.