Lesson 5 - Brewing Water Composition and Impact SAQ

**Minerals in the brewing product water can positively influence yeast and beer flavour. In some cases, there can be too much of a good thing. In other cases, small amounts can have a detrimental impact on the final beer. Discuss how mineral levels in the product water can negatively impact the final beer.

Response:

This answer will list the key points.

Copper – Copper inhibits enzymes and can become toxic to yeast when levels exceed 10 mg/L. It is an oxidation catalyst, affecting flavour and colloidal stability.

Iron – Iron inhibits yeast, causing incomplete saccharification. It can reduce beer body and create an insipid flavour. Iron also discolours foam and causes a metallic flavour. It is an oxidation catalyst, affecting both colloidal and flavour stability.

Manganese – Manganese may inhibit fermentation at levels above 0.5 mg/L.

Nitrate/Nitrite – Nitrates can be reduced to nitrites, which are poisonous to yeast cells.

Sodium – Sodium quantities greater than 150 mg/L can lead to salty/sour notes in the beer.

Chlorine – Chlorine can cause off-flavours (chlorophenol) and be toxic to yeast, which will lead to incomplete fermentations and other off-flavours.

Chloride – Chloride levels higher than 300 mg/L can give a paste-like or salty taste. Levels higher than 500 mg/L can be toxic to yeast.

Magnesium – Magnesium levels higher than 15 mg/L can cause a sour/bitter taste.

Potassium – Potassium can make the beer taste salty at levels higher than 500 mg/L.

Sulphate – Sulphate can act as a precursor to hydrogen sulphide and sulphur dioxide. Levels higher than 400 mg/L can cause astringent and unpleasant bitterness.

Zinc – High levels (> 5mg/L) of zinc can cause astringent flavours, but levels higher than 0.5 mg/L can be poisonous to the yeast, creating off-flavours.