Lesson 4 - Brewing Water Composition and Impact
This lesson deals with the influences of water composition on brewing equipment, the brewing process and beer quality. It will cover the positive and negative impacts that the various compounds found in water have on beer. We will explore the recommended water specifications for brewing key beer styles. We will also examine how to correct levels of some of the key salts within water.
Adjusting Water Mineral Content
In this section, we will explore options for adjusting water characteristics.
The brewer should not be tempted to over-mineralise the water, as this can unintentionally change the mash pH out of the target range and also make the beer taste less pleasant!
Calcium addition
Throughout this lesson, we have seen that calcium is a key mineral and is involved in a number of processes. If the source water is particularly soft, the calcium levels may be too low; additional calcium will need to be added to the water. The two most common ways are by adding either calcium chloride CaCl2.2H2O or calcium sulphate CaSO4.2H2O. Does that ring any alarm bells? Yes, by adding one of these calcium salts, you risk increasing the level of certain ions in the final beer beyond the point where they provide a desirable or indeed acceptable palate.
Calcium chloride addition
The chemical formula for calcium chloride is CaCl2.2H2O. This has a molecular weight (mw) of 147. We calculate this as follows (based on the atomic weight of each element):
Ca = 40
Cl = 35.5
H = 1
O = 16
Therefore 40 + (35.5 x 2) + [2 x (2+16)] = 147
The calculation for calcium addition is then:
Amount of CaCl2.2H2O to add = mg of Ca wanted x (mw CaCl2.2H2O / mw of Ca)
Amount of Cl added = amount of CaCl2.2H2O added x (2 x atomic weight Cl / mw CaCl2.2H2O)
So, to add 10 mg/L of calcium, you would need to add 10 x (mw CaCl2.2H2O / mw Ca) = 10 x 147 / 40 = 36.75 mg/L of CaCl2.2H2O. This would also add 36.75 x 71 / 147 = 17.75 mg/L of chloride!
Another way of looking at this is the addition of 1 g per L of calcium chloride will give:
1,000 mg/L CaCl2.2H2O = (147 / 40) x Ca
Ca = (1,000 x 40) / 147 = 272 mg/L
And
1,000 mg/L CaCl2.2H2O = (147 / 71) x Cl
Cl = (1,000 x 71) / 147 = 483 mg/L
Calcium sulphate addition
The other recommended calcium salt is calcium sulphate CaSO4.2H2O. Let us follow a similar logic to that used with calcium chloride.
The chemical formula for calcium sulphate is CaSO4.2H2O. This has a molecular weight (mw) of 172. We calculate this as follows (based on the molecular weight of each element):
Ca = 40
SO4 = 96 (made up of 32 + 16 x 4)
H = 1
O = 16
Therefore 40 + (96) + [2 x (2+16)] = 172
The calculation for calcium addition is then:
Amount of CaSO4.2H2O to add = mg of Ca wanted x (mw CaSO4.2H2O / mw of Ca)
Amount of SO4 added = amount of CaSO4.2H2O added x (mw SO4 / mw CaSO4.2H2O)
So, to add 10 mg/L of calcium, you would need to add 10 x (mw CaSO4.2H2O / mw Ca) = 10 x 172 / 40 = 43 mg/L of CaSO4.2H2O. This would also add 43 x 96 / 172 = 24 mg/L of sulphate!
Another way of looking at this is the addition of 1 g per L of calcium sulphate will give:
1,000 mg/L CaSO4.2H2O = (172 / 40) x Ca
Ca = (1,000 x 40) / 172 = 233 mg/L
And
1,000 mg/L CaSO4.2H2O = (172 / 96) x SO4
SO4 = (1,000 x 96) / 172 = 558 mg/L
When deciding which salt to use, look at the base product water to see which of the chloride or sulphate ions can be elevated without negatively affecting the overall flavour perception. You must also consider other impacts that chloride and sulphate ions have on the brewing process, brewing plant and the final beer quality.
Chloride or sulphate addition
If you want to elevate either chloride or sulphate to achieve the correct ratio between the two, there are several options available.
We have just explored adding calcium chloride or calcium sulphate. However, if there are issues with adding too much calcium, we could consider the following salts instead:
- Sodium chloride (NaCl – mw 58.4)
- Potassium chloride (KCl – mw 74.6)
- Potassium sulphate (K2SO4 – mw 174.3)
- Magnesium chloride (MgCl2.6H2O – mw 203.3)
- Magnesium sulphate (MgSO4.7H2O – mw 246.5)
To know how much to add, follow the same process as you did with calcium.
To avoid excessive consumer salt intake, be careful not to add too much sodium chloride. You should also exercise caution when adding magnesium salts as they have laxative properties.
One final note of caution. When it comes to salt additions and the ionic composition of beer, what goes in is not what comes out. It is essential that we measure the impact of adjustments we make to the water on the ionic composition of the finished beer. It is also vital that the beer before and after adjustment is subject to statistically robust sensory evaluation to establish that any changes are desirable to the consumer.