Coffee extraction is the science behind brewing a cup of coffee. It is made up of a number of factors, but in simplest terms, it is the correct quantity of precisely ground coffee, that has the optimal amount of flavours extracted from it, by controlling the time and temperature of the water. When talking about the perfect cup of coffee the two major qualities are strength and extraction.
Strength has to do with the concentration of the coffee, how concentrated or watery the coffee is. If the coffee has low strength it will taste watery and be weak, if the coffee has been brewed too long it will be over concentrated and too strong.
Extraction has to do with how much of the coffee has been dissolved into the water. If many of the compounds in the coffee are not released into the water it will but under developed and not very flavorful. If too much of the coffee flavour is extracted the taste can become very bitter.
Looking at the chart we can see the ideal balance of strength and extraction lies in the middle at around 20% extraction and 1.25% strength. The red lines represent the amount of coffee grinds per 1.9L of water. Using to little grinds will result in strong concentrated coffee that has little flavour because not enough coffee is able to dissolve. Using too much ground coffee will result in a watery coffee that is bitter tasting because too much coffee is able to dissolve and will be over extracted before a desired strength can be reached.
At the end of the day most coffee lovers agree that about two tablespoons of ground coffee to 180ml of water is the optimal ratio. This is because the coffee brewed in this manner has the greatest chance to fall in that ideal balanced zone of strength and Extraction with minimal effort.
