Water Quality for Coffee Beverages
Water Quality for Coffee Beverages
Recently a study was published in the Journal of Agricultural Food Chemistry (see here) regarding water quality for brewing the perfect cup of coffee. The study and subsequent media articles are based on research conducted in the UK by Christopher Hendon, a PhD student from the University of Bath’s Centre for Sustainable Chemical Technologies, and Maxwell Colonna-Dashwood, owner of Colonna and Small’s coffee shop in Bath, UK, who is also the current UK Barista Champion. Mr. Colonna- Dashwood is a finalist in the World Barista Championship competition being held in Rimini, Italy.
The research used computational chemistry to determine the relationship between water quality and specific parameters of roasted coffee to produce the highest quality beverage and to manage variations in coffee taste.
Spencer Turer, Coffee Analysts’ Vice President, was interviewed by Outside Online (see here) to help explain this research and the relevancy for specialty coffee retailers. Since the articles posted on this important topic have been brief, below is more information which coffee professionals may find useful.
Coffee beverages are made up of about 98%-99% water. The remaining 1%-2% are brew solids that are extracted from the ground coffee. At these rates, it is very important to use high quality water along with fresh, high quality coffee to produce coffee beverages.
The Specialty Coffee Association of America has established the following water quality guidelines:
| Characteristic | Target | Acceptable Range |
| Odor | Clean / Fresh, Odor free | |
| Color | Clean color | |
| Total Chlorine | 0 mg/L | |
| Total Dissolved Solids | 150 mg/L | 75 – 250 mg / L |
| Calcium Hardness | 4 grains or 68 mg / L | 1-5 grains or 17mg/L – 85 mg/L |
| Total Alkalinity | 40 mg/L | At or near 40 mg/L |
| pH | 7.0 | 6.5 -7.5 |
| Sodium | 10 mg/L | At or near 10 mg/L |
SCAA Standard | Water for Brewing Specialty Coffee (SCAA Water Standards)
The research conducted by Mr. Hendon and Mr. Colonna-Dashwood is accurate stating that different ions in the water will effect extraction differently. SCAA water quality standards do not specifically address individual dissolved solids, only the total dissolved solids. The research determined that different proportions of various dissolved solids affect the extraction and will affect that flavor of the coffee beverage. Mr. Hendon explains, “Hard water is generally considered to be bad for coffee, but we found it was the type of hardness that mattered – while high bicarbonate levels are bad, high magnesium levels increase the extraction of coffee into water and improve the taste.” The study also determined that water softeners commonly increase the sodium content in water which does not help the flavor of coffee.
In addition to water quality, there are many aspects of the roasted and ground coffee product that are under the control of the coffee roasters and baristas that will also affect the rate of extraction and the flavor of the coffee beverage. The coffee variables are:
| Variable | Effect |
| Bean origin | Not all beans have the same chemical composition. |
| Bean roast | The chemical composition of the coffee bean changes throughout the roasting process. |
| Size of coffee grindings | A consistent particle size is important, as the higher the surface area, the faster the extraction. |
| Dry mass of coffee grindings | A different extraction composition. |
| Temperature of extraction | The temperature dictates both the rate and composition of the extraction. |
| Pressure of extraction | Has a similar effect as temperature. |
| Time of extraction | Increasing extraction time allows for greater extraction. |
| The water | The variable is less obvious, but it is clear that the chemical composition of water (i.e. dissolved ions) play a very important role. |
Schrödinger’s water for perfect cup of Coffee, Chemistry World Blog 6/11/2014 (credits)
In a café or foodservice environment it is highly recommended to utilize a water treatment system to manage the water quality used for coffee brewing. Municipal water may vary in quality and should not be uncontrolled when preparing coffee beverages. It is not feasible for every specialty coffee café or foodservice location to thoroughly test their water quality as one would in a food science laboratory using gas chromatography-mass spectrometry equipment, especially considering the variability of water quality.
Mr. Colonna-Dashwood is using his expertise as a professional coffee roaster and champion barista to specifically design a coffee to be used in the World Barista Championship competition. He started by evaluating the local water to be used for the competition.
It is unknown if the level of detail used by Mr. Colonna-Dashwood in his preparations for the World Barista Championship, and the level of chemical details researched by Mr. Christopher Hendon will be detectable by a consumer of coffee beverages. As of the writing of this article it is evident that the expert sensory judges have appreciated the flavor or Mr. Colonna-Dashwood’s espresso, cappuccino and signature drinks, thus earning him a place in the finals amongst the top 6 Baristas in the world for 2014.
After a café or foodservice location is able to control the water quality, the next step as illustrated above is to design a specific roasted coffee product to maximize the extraction and produce a high quality, great tasting beverage. However, since café’s generally serve more than one coffee product, and very often utilize a variety of brewing techniques, including automatic drip, manual pour, aeropress, siphon, French press, and espresso it is unknown if the pairing of a specific coffee to the individual ions found in the water will produce the same high quality beverages in all equipment. It is also unknown if the financial investment and time required for research and development of these specific coffee products as well as management of individual ions in the water will be recognizable and appreciated by the consumer, especially after steamed milk is incorporated into the beverage or after sweeteners are added to modify the flavor to the consumers own preference.
Mr. Colonna-Dashwood is asking all the right questions and helping to conduct relevant and important chemical research into water quality that will ultimately help all baristas prepare higher quality coffee beverages, and I applaud his efforts.
