Let's see few definitions: TDS = Total Dissolved Solids = solids dissolved in the brew PE = Percent Extraction = percent of solids extracted from the dry coffee grounds
The percent extraction can be calculated by the formula: PE = TDS × Rm
where Rm = ratio between the mass of the brew and the mass of dry grounds
Now, you need to consider the following facts: 1) every 1g of coffee absorbs 2g of water 2) the given brew ratio is 1:15, which means that for every 1g of grounds we use 15g of water
Let's call x = grams of coffee grounds we want to use Therefore the mass of the brew will be: m(brew) = water we use - water absorbed by the coffee = 15·x - 2·x = 13·x
Therefore, Rm = m(brew) / x = 13·x / x = 13
Hence, the percent of extraction will be: PE = <span> TDS × Rm = 1.4 </span>× 13 = 18.2
