Water Quality for Coffee

SCAE Water Report (2016)

The Zurich University of Applied Sciences (ZAHW) in collaboration with the Specialty Coffee Association (SCA) produced a comprehensive report on water quality for coffee. This study focuses on the chemical composition of water, particularly the concentrations of calcium, magnesium, bicarbonate, and other ions. The report outlines how these elements influence both coffee flavor extraction and equipment longevity. Key recommendations include:

  1. Total hardness, alkalinity, and pH are the three central measures to characterize water.
  2. Traditional hardness units (ppm CaCO3, °d, °f) provide an easy and accurate way to assess a water’s suitability for use in coffee extraction.
  3. With regard to sensory aspects, the acid buffer capacity should be referred to as alkalinity. Note that “carbonate hardness” is not necessarily the same as alkalinity.
  4. Water for coffee extraction should
  • be odour free and hygienic. The water should be completely free of chlorine, hypochlorite and chloramines, as well as taste-influencing organic compounds, since these can impart a strongly unpleasant flavour in the resulting brew even at concentrations which are not perceivable in the water itself.
  • have a total hardness of 50–175 ppm CaCO3 (2.9–9.8 °d). • have an alkalinity of 40–75 ppm CaCO3 (2.2–4.2 °d). • have a pH of 6.5–8.
  • have an electrical conductivity (in µS/cm corrected to 20°C) less than three times the alkalinity (in ppm CaCO3)

Comment: This report is highly detailed and practical, providing specific guidelines that can be directly applied in coffee brewing operations and equipment maintenance. Its focus on a balanced approach to flavor and equipment care is particularly useful.

 

Another scientific study about water for coffee was perfomed by Colonna & Hendon in 2015. They published it in a book called “Water for Coffee” and most of the conclusions were then confirmed by ZHAW, but the first recommendations concerning water quality for coffee were published by the SCAA before 2010. So, it is relatively recent that water was really investigated in terms of chemical and physical properties.