Taste and Flavour
Coffee Water’s Evolution in the Third Wave
As the specialty coffee movement began to advance in the early noughties, it took a long while for folks to realise how much of an impact water was having on their coffee quality. Our first key discovery in the way thechemistry of water impacted coffee quality was that roasters in soft water regions roasted darker than those in hard water areas. Over time, this widespread tendency came to be explained by the increase in the amount of buffer in the water in hard water areas.
Roasters using soft water in their cuppings will taste more sourness and acidity because they have less buffer available to reduce the acidity. They will therefore naturally attempt to reduce the acidity through the roasting process. Hotter, longer roasts will reduce the acidity of a coffee through the degradation and evaporation of acids. Roasters cupping with hard water tended to roast much lighter to try to boost the acidity of their roasts. They were missing out on a lot of flavour as their fruity tastes were buffered away by an excess of temporary hardness.
An infographic showing how a roaster with hard water will tend to roast lighter and a roaster with soft water will tend to roast darker
These days, specialty coffee roasters ship coffees long distances to clients and subscribers, often crossing international borders. This means hard-water roasters will sell to soft-water cafes, and vice versa. Best practice suggests that cafes and roasteries should consider using similar water recipes so the cafe can achieve flavours similar to those of the roaster.
Over time, water recipes across the specialty coffee world have come to be much more similar than they once were. However, attempts to exactly recreate the water chemistry of a roastery are more complex than once thought. This is because it is very difficult to alter the balance of magnesium and calcium ions in our water without reverting to remineralisation.