Lesson 3 - Brewing Water Sources and Treatment SAQ

**Discuss temporary water hardness. What is it and how does it impact the brewhouse process?

Response:

Temporary hardness can be removed by boiling as the carbonate or bicarbonate salts of calcium or magnesium precipitate out. This is different from permanent hardness, which cannot be removed by boiling.

The brewhouse process is hot, which can ultimately lead to the carbonates and bicarbonates precipitating out and causing scaling in pipes and heating surfaces. This in turn leads to reduced heat transfer efficiencies.

The minerals making up water hardness can affect mash and wort pH, as the ions causing temporary hardness generally raise the pH.

The following equations help to explain the impact that temporary hardness can have on wort:

(Equation 1)

Ca(HCO₃)₂ ↔ CaCO₃ ↓ + H₂O + CO₂ ↑                                               

(Equation 2)

Equation 1 describes what happens when we boil water with temporary hardness. Calcium carbonate CaCO₃ is formed and precipitates out of the solution, whilst CO₂ is released.

Equation 2 (a detailed breakdown of what is happening to these compounds) shows that these compounds act as weak bases, and raise the water pH (or mash) because hydroxyl ions (OH^-) are produced and CO₂ (which is acidic) leaves the system.

If left uncorrected, the wort will become more alkaline; this can be detrimental as it can cause:

• Poor saccharification
• Poor wort separation
• Dark worts
• Poor biological stability
• Poor protein precipitation
• Astringent beer (polyphenol extraction)

Although, higher wort pH does improve hop isomerisation.

Temporary hardness is also related to total alkalinity, as the total alkalinity is defined as the amount of strong acid (such as HCl) required to convert the carbonate and bicarbonate in the sample to carbon dioxide at a pH of 4.4. We have shown that carbonates and bicarbonates can raise the mash pH, but they can also react with the malt’s phosphates. During the mashing process, the malt’s phosphates react with calcium in the water to precipitate calcium phosphate. The reaction releases hydrogen (H⁺) protons that react with carbonates in the water to create water and CO2. This reduces the alkalinity and lowers the pH.

Any alkalinity that remains after reacting with phosphates is known as the residual alkalinity, which increases the mash pH.

Brewers may want to add calcium to their brew in the mash tun in order to support yeast flocculation. They should think carefully before doing this as it can affect pH.