From a taste and flavour perspective, there is an association of increased bitterness and astringency in over-extracted brewed coffee.
There is an association with vegetal and sour flavours in under-extracted brewed coffee.
There are gradients of extraction in every cup owing to the undesirable spread of particle sizes in ground coffee. This means extraction is an average.
In 1959, the first Brew Control Chart was developed by Earl E. Lockhart and a sensory panel. The 18-22% extraction yield target was established for filter coffee which has continued relevance today.
Extraction target ranges can be redrawn when the spread of grind size particles is reduced.
Similarly, when using inferior coffee equipment, results are usually better when you target lower extraction yields.
When you know any three of the four key brew parameters, of TDS%, Extraction %, Dose, and Beverage Weight, you can use coffee algebra to work out the unknown quantity.
Applying these equations helps clarify your understanding of how coffee apps and spreadsheets work.
It helps you locate recipe details to make your brewing more accurate.
We introduced you to a new set of calculators in a toolkit which will help you, not only with the certification process in the course, but will also be something to take home.
Double Hump: a term explaining the marginal gains in coffee flavour when under extracted brews are optimised for ‘surface extraction’, usually involving inferior coffee equipment.
Sensory Science: a scientific discipline that uses statistics and experimental design to obtain objective quantitative data about organic products.
Surface Extraction: where the solute is removed from the outsides of coffee grinds through a process of erosion,