Coffee Quality: How Much of it is the Water?

Can water have a huge influence on the way coffee tastes? It has always been clear that, with it being 98% water, water is the most important ingredient in coffee preparation, but, nowaday,s its importance is clearly definable by Specialty Coffee Association (SCA) Standards.

SCA standards for minerals:

• Total hardness of 50-175 ppm CaCO₃ (2,9-9,8 dH°)
• Carbonate hardness of 40-75 ppm CaCO₃ (2,2-4,2 dH°)
• Total hardness should exceed carbonate hardness
• pH of 6,5-8

(ppm equals here mg/l) 

Just to make clear it a little clearer as it may not be totally obvious:

Total hardness

The amount of Magnesium and Calcium ions is also known as total hardness (often measured as °dH).

Magnesium and Calcium are key minerals for extracting taste.

Magnesium attracts oxygen and a lot of flavorful compounds, so it is generally a better extractor than Calcium.

Calcium easily bonds with other substances. Together with carbonate hardness level, it causes the formation of limescale. Magnesium is not easily bonding, so it rarely causes limescale formation.

Carbonate hardness kH

Bicarbonate, and some other carbonates, originated from the carbonic acid that paired up with Magnesium and Calcium.

Carbonate hardness is considered a sort of  temporary hardness, while the boiling process precipitates the minerals.

But, definitively, carbonates cover the lion’s share of coffee preparation. The best way to make a horrible cup of coffee is not to take them into account!

Carbonates control acid buffer capacity. This means the ability to keep pH stable. The acidity of the coffee batch changes depending on the carbonate hardness due to the buffering capacity of the carbonates.

• In the case there is high carbonate hardness in water, the positive acidity in taste (i.e. citric, fruity, sour etc.) will be flushed away by the pH buffer. The acidity itself is still there, we just don’t find it in the taste, only earthiness and a dull, flat taste.
• In the case of low carbonate hardness, the coffee taste is vinegary and sour.

On the other side of hardness there is permanent hardness, we talk about this when we refer to non-carbonate anions (= nitrates and sulfates) that pair up with Magnesium and Calcium. Permanent hardness causes soft chalky or muddy sediment.

In water there are other dissolved ions that contribute to the taste of water, it, of course, has to be clean and without any particular smells or flavors, such as chlorine, chloramine and hypochlorite!

But, getting to the point, the total amount of dissolved substances depends on the type of extraction that we utilize, espresso versus filter coffee shifts the optimum amount of total hardness and carbonate hardness towards higher values. It is, therefore, impossible to determine the exact amount of dissolved substances that make water suitable for every type of coffee, as brewing method has a stark importance on the soluble presence in the final cup.

So, it’s not only the quantity but also the pressure, temperature and brewing method that determines the significant rule of water in coffee preparation.

The best starting point is always fresh, cold water.

Yes! It has to be cold! The art of coffee has nothing to do with rushing.