Water is highest percentage in any brewed coffee beverage, between 98% and 99% in the case of a filter coffee or around 92% in the case of an espresso. It is therefore important to pay the necessary attention to this essential component of the beverage which can have a significant influence on the taste and aroma of the coffee.

Each coffee bean is made of both soluble and insoluble solids. Applied at the right temperature for each preparation and with appropriate composition, hardness, alkalinity and pH characteristics, water works as a solvent for these soluble components responsible for the aroma and flavour of the coffee, extracting its full sensorial potential.

Using an inappropriate water can change the sensorial profile of a coffee, dulling or increasing its acidity to undesirable proportions or adding flavours or odours that do not really belong to the resulting brew.

Thus, for the preparation of specialty coffee, the whole community agrees that it is essential to use the right water to allow us to perceive the true potential of each coffee.

The SCA (Specialty Coffee Association) has carried out different research studies that are currently used as a framework for the water used in the preparation of specialty coffees.

For the correct extraction of coffee soluble solids, the brewing water should have these characteristics:
 

The water used for coffee should be fresh, clean and odourless, free from chlorine compounds, iron or organic matter that may add undesirable odours or flavours even at concentrations of chemical compounds that are not detectable in the direct taste of the water.

From a sensory point of view, the main characteristics to be considered are:

• Total hardness, as it directly affects extraction. The recommended hardness is between 51 and 175 ppm. The balanced presence of these minerals in the water is essential, as they have a sweeping effect on the coffee solubles, helping them to be extracted correctly.


• Alkalinity, as it directly influences the perceived acidity. An excess of alkalinity will extinguish the natural acidity of the coffee itself, while a low alkalinity will give the coffee an acidity that does not correspond to it.


• Finally, the pH, the measurement of which indicates the acidity or alkalinity of the water. A pH 7 is a neutral pH, with acceptable values being between 6 and 8. Values below 6 indicate excessively acid water, while values above 8 are indicative of excessively alkaline water.

Putting these three elements in relation to each other, for a correct water composition the alkalinity should be approximately 1/3 of the total hardness, with these values leading to an orientation of the pH towards its neutral value.

Once the right water has been selected and depending on the brew to be made, other factors must also be taken into account in the relationship between water and coffee, among which we can highlight:

• Coffee - water ratio. An optimal ratio of coffee to water will ensure that the sensory properties of the coffee are correctly expressed, as these quantities have a direct effect on the strength of the drink.


• Water temperature. The temperature of the water affects its extraction capacity. If the water is applied at the recommended temperature for each preparation (where other factors specific to each preparation will also come into play), the aromatic and flavour components will be correctly extracted.

The quality of the water and its correct application are fundamental for the correct extraction of coffee. A distilled water, with no mineral content, will not be able to extract the soluble solids from the coffee, while excessively hard water can lead to low extraction and undesired flavours, which are not present in our beans. Following the recommendations and paying attention to the appropriate water composition will allow us to obtain the full sensorial potential of each coffee.

Source: 

- The SCAE Water Chart. Measure aim treat. Marco Wellinger, Samo Smrke and Chahan Yeretzian. Zurich University of applied sciences. Specialty Coffee Association of Europe.
- SCA Coffee Standards. Specialty Coffee Association. www.sca.coffee