Beer is mainly water, with some alcohol and flavour compounds. It is therefore natural that the brewing water composition has a huge influence on the beer profile.
We know that water is made of hydrogen and oxygen and that it is a solvent which can dissolve minerals such as carbonates, calcium, magnesium etc.
Those minerals are widely present in brewing water and it is therefore important to understand their impact and how to tweak them to optimise the desired flavour.
The first thing to consider is the influence of those minerals on pH. During mashing, calcium and Magnesium will react with substances extracted from the malt (mainly phosphates) and will lower the pH.
Carbonates and bicarbonates will on the other hand increase the mash pH.
For now, we will be looking at the three main mineral ions that will influence your brew: Calcium (Ca), Sulphate (SO4) and Chloride (Cl).
Calcium is very important as it plays a key role at many different levels:
- It decreases the mash pH by precipitating calcium phosphates and releasing hydrogen ions,
- Stabilises malt enzymes during mashing.
- Precipitates oxalate ions (improved clarity and reduced gushing),
- Improves ‘hot break’ formation,
- Restricts colour formation during wort boiling,
- Works as a co-factor for amylolytic and proteolytic enzyme activity improving brewhouse extract,
- Aids yeast flocculation.
We may want to keep in mind that a too high level of calcium increases the water hardness which can cause scaling. Adding too much can also excessively lower the mash pH which can reduce the bittering compounds extraction from hops,
Depending on the beer style you are brewing, the types of malt used and the water alkalinity, calcium levels should be kept between 50 and 150mg/l.
Sulphates and chlorides are looked at as a ratio between them. Even though the level of each ion is important, it seems that their ratio is what matters most. Higher levels of sulphates are thought to increase the bitter hop character while chlorides will enhance malt sweetness.
For hop forward beers such as IPAs, a ratio of 3 sulphates to 1 chloride would be recommended to support bitterness and leave more space for the hops to shine. Sulphate levels for pale ales are usually found at around 50-150mg/l and above 200mg/l for IPAs.
Too much sulphates can result in an overpowering bitterness and astringency(<400mg/l).
Sulphates also are precursors to hydrogen sulphide and sulphur dioxide during fermentation.
On the other hand, for fuller bodied, malt forward beers, a ratio in favour of chlorides would be recommended. 2 chlorides to 1 sulphate would be the norm with levels around 50-150mg/l. In excess, chlorides can lead to fermentation and yeast floculation issues and overpowering mouthfeel.
So how to manage those ions to make the best out of my recipe?
The obvious first thing to do is to get your brewing water’s physico-chemical analysis report to have an overview of its ionic composition and decide what should be adjusted to match with your recipe.
The most common way of adjusting mineral levels is by using the following salts:
- Gypsum – Calcium sulphate
- Calcium chloride
These two can be used to adjust the sulphate-chloride ratio but they will at the same time increase the calcium level. If the calcium level is already high, magnesium chloride and magnesium sulphate (epsom) can be considered.
Now, how to dose those salts?
To calculate the required salt addition, we need to consider their chemical composition and the molecular weight of each element:
Calcium – Ca: 40
Magnesium – Mg: 24,3
Chloride – Cl: 35,5
Sulphate – SO4: 96 (32 + 4x16)
Hydrogen – H: 1
Oxygen – O: 16
The formula for Calcium chloride is CaCl2H4O2, therefore its molecular weight is 40 + 2x35,5 + 4x1 + 2x16 = 147
We can then cross multiply those values to find out how much calcium chloride we need to add for a determined amount of either calcium or chloride:
Mg/l
So for each gram of calcium chloride used, we are adding 27,2% of that weight of calcium and 48,3% of chloride.
We can see here that indeed, 100g of calcium represents 27,2% of 367,5g of calcium chloride and 100g of chloride is 48,3% of 207,04g.
The same logic can be applied to calcium sulphate (gypsum). Its formula is CaSO4⋅ 2H2O so its molecular weight is 40 + 96 + 2x(2+16) = 172
And the reverse is follows of course the same logic. If I add 100mg/l of gypsum, how much sulphate would that give?
For 100mg/l of gypsum added, I will increase my sulphate levels by 55.81mg/l, This can be verified by the fact that the molar mass of sulphate (96) represent 55,81% of the molar mass of calcium sulphate (172).
If the level of calcium is already high and adding more may be an issue, magnesium sulphate and chloride can be used instead. The logic remains the same.
- Magnesium – mw 24,3
- Magnesium chloride – mw 203.3
- Magnesium sulphate (Epsom) – mw 246.5
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