Lesson 5 - Brewing Water Composition and Impact SAQ

**Your base product water has a calcium level of 150 mg/L. The chloride and sulphate levels are both 0 mg/L. You would like to have chloride levels up to 100 mg/L, and a sulphate level of 300 mg/L. You will need the following information:

mw of sodium chloride (NaCl) is 58.4

mw of chloride (Cl) is 35.5

mw of sodium (Na) is 23

mw of magnesium sulphate (MgSO₄.7H₂O) is 246.5

mw of magnesium (Mg) is 24.3

mw of sulphate (SO₄) is 96

a) What type of beer style would this be suitable for, once the sulphate and chloride levels have been adjusted?

b) Why would you not add calcium chloride or calcium sulphate to this water to get the chloride and sulphate levels to the target level?

c) Calculate how much sodium chloride would need to be added to achieve the target chloride. What impact would this have on the beer?

d) Calculate how much magnesium sulphate you would need to add to achieve the sulphate target. What impact would this have on the beer?

Response:

a) An Amber ale, as the mineral levels for this style should have a calcium level between 50-150 mg/L, with chloride levels between 50-150 mg/L and sulphate levels between 100-300 mg/L.

b) The calcium levels are already high. Adding further calcium could cause the pH to drop lower than desired. The target water specification suits an amber ale, which uses darker malts to help achieve the colour and flavour profile. These darker malts tend to acidify the mash. Thus, adding calcium could reduce the mash pH too much.

c) The chemical formula for sodium chloride is NaCl. This has a molecular weight (mw) of 58.4.

The calculation for chloride addition is then:

Amount of NaCl to add = mg of Cl wanted x (mw NaCl / mw of Cl)

Amount of Na added = amount of NaCl added x (mw Na / mw NaCl)

Therefore:

Amount of NaCl = 100 x (58.4 / 35.5) = 164.5 mg/L

Amount of Na added = 164.5 x (23 / 58.4) = 64.8 mg/L

The amount of sodium added would be 64.8 mg/L, which is higher than the recommended level for brewing water (< 50 mg/L). However, sodium levels below 150 mg/L contribute to a full and sweet palate, which could be beneficial to an amber ale. The sodium levels will help support the malt’s sweetness and create a fuller flavour beer. The target chloride:sulphate level will be 1:3, which would support the beer’s bitterness. Thus, the two working together could help to balance out the bitterness. We should note that high levels of sodium are detrimental to consumer health.

d) The chemical formula for magnesium sulphate is (MgSO₄.7H₂O). This has a molecular weight (mw) of 246.5.

The calculation for sulphate addition is then:

Amount of MgSO₄.7H₂O to add = mg of SO₄ wanted x (mw MgSO₄.7H₂O / mw of SO₄)

Amount of Mg added = amount of MgSO₄.7H₂O added x (mw Mg / mw (MgSO₄.7H₂O))

Therefore:

Amount of MgSO₄.7H₂O to add = 300 x (246.5 / 96) = 770.3 mg/L

Amount of Mg added = 770.3 x (24.3 / 246.5) = 75.9 mg/L

The amount of magnesium added is higher than the recommended level of < 40 mg/L. Some of the magnesium added may bind with phosphates in the malt during mashing and precipitate out, thus dropping the overall amount available. However, most phosphates will more likely bind to calcium first. High levels of magnesium can cause a sour/bitter taste, which may support the beer’s overall bitterness. However, high magnesium levels can have a laxative effect! Therefore, it may be better to use an alternative source of sulphate, such as potassium sulphate.