As we begin, I’d like to offer a quick primer on what a brew ratio is. Simply put, a brew ratio is the ratio of coffee to water in a coffee brewing recipe. For example, if your brew ratio is 1 to 16 (often expressed 1/16), then for every one part coffee, you use 16 parts water. In other words, to prepare 16oz cup of brewed coffee you would use 1oz of ground coffee and 16oz of water, or 30g ground coffee to 475 ml of water for those using the metric system (1, see below).
Brew ratios are a crucial element of coffee brewing because coffee is a solution produced by using water (a solvent) to dissolve and extract flavor molecules from ground coffee (a solute). The ratio of solute to solvent, in this case coffee to water, determines the amount of flavor molecules available for extraction and the volume of the solution they are being extracted into. As a result, if other variables are held consistent (grind size, water temperature, agitation, etc.), this ratio determines the concentration of coffee solids in the resulting beverage. In other words, the concentration of extracted solids, often colloquially called the strength of a cup of coffee, is determined by the brew ratio.
Brew ratio and cup strength have a strong effect on the type and intensity of that cup’s sensory qualities. For example, if your brew ratio is very close, say 1/2, the resulting coffee will have a high concentration of extracted coffee solids. This means that whatever strong flavor characteristics the coffee has, such as heavy mouthfeel or intense acidity, will be especially pronounced. The opposite is also true; a ratio which is far apart, such as 1/20, will result in coffee which has a low concentration of extracted coffee solids. This means that flavor characteristics are more gently expressed, with strong mouthfeel or acidity manifesting more delicately. The analogy of music functions well to describe this; using different brew ratios for the same coffee is like playing the same song with different arrangements. The tune is still recognizably the same, but the expression of individual instruments and elements in the music differs slightly, which displays both the complexity of the underlying music and the artistry of the arranger, or in this case, the individual brewing the coffee.
To continue this analogy, if every coffee is a different piece of music, then different arrangements, i.e. brew ratios, will suit each one differently; some coffees taste wonderful at very close ratios, and others taste great at ratios which are very far apart. For example, take a coffee with a very delicate flavor profile, such as a washed Ethiopia Yirgacheffe with notes of honey and jasmine. Brewing this coffee at a very close ratio is possible but will likely obviate some of its more interesting flavor characteristics; high extracted solid concentrations might turn the floral notes into bitterness, muting the sweetness and making for an unpleasant cup. A coffee like this is likely better suited to a brew ratio which is reasonably far apart, which allows for more gentle extraction and preservation of its subtler flavor characteristics. The opposite might be true of a darkly roasted blend, where a closer brew ratio might accentuate desired flavor intensity or bitterness; brew ratios can vary both by coffee and by the brewer’s preferred outcome.
Ideal brew ratios also vary by coffee brewing method. Espresso, for example, uses a much closer brew ratio than filter coffee, with espresso sitting around 1/2 and filter around 1/16. Espresso requires a close ratio because it is brewed using pressure. Pressure speeds up extraction and concentrates the extracted coffee solids, which necessitates a small brew volume; espresso coffee is a deliberately intense experience, and if it were extracted at a filter ratio, it would be too diluted to taste good. Filter coffee, on the other hand, merely uses gravity to aid in extraction. This allows for a brew ratio which is far apart and extracts gently, producing a very rounded flavor profile at a higher brew volume. In this sense, different brewing methods are defined by their varying tolerances for different brew ratios. Just as some brew ratios suit individual coffees better than others, so too do different brew methods; all coffees are different, and the brew ratios and brewing methods used to prepare them must reflect that.
In conclusion, brew ratios are a crucially important element of coffee preparation. Determinants of brew strength and flavor expression, understanding how different coffees are suited to different brewing methods and brew ratios is the key to making delicious coffee consistently. I hope this look into brew ratios has been informative. Stay tuned to this blog for more of all things coffee. Until next time.
1 The actual resulting cup will be a slightly lower than 16oz/475ml in volume, as some water always remains trapped in the coffee grounds.