Bicarbonate

Bicarbonate ion (HCO₃^–) is often present in tap water in fairly high levels, and it is responsible for the alkalinity of water because it a weak base that neutralizes acid. Effectively, any bicarbonate in the brewing water directly increases mash pH (and sparging pH, if applicable), which carries forward to affect the boil pH, fermentation pH, and beer pH. This is problematic for pale beer styles since the mash pH typically need to be lowered, not raised. Alkalinity is arguably the most important parameter of the brewing water due to the critical role that pH plays in the brewing process and the tremendous effect it has on beer quality. In order to avoid an excessively high pH during mashing (and sparging), it is often necessary for brewers to neutralize excess alkalinity either by adding a mineral acid (e.g. lactic acid), or by other methods (see brewing pH). The levels of calcium and magnesium in the brewing water also counteract the pH effects of the bicarbonate. Sometimes, the amount of alkalinity in water is expressed as mg/L CaCO₃, which can help to compare the potential pH effect of the alkalinity versus the aforementioned calcium and magnesium levels when they are also expressed as mg/L CaCO₃.

There is no bicarbonate ion present in beer because bicarbonate is a base, and beer is acidic. During the brewing process the bicarbonate is removed either by reacting with acid to form carbon dioxide and water, or by combining with a cation such as calcium to form an insoluble product that is removed.

Potential sources of bicarbonate

Typically the bicarbonate comes solely from the brewing water. In styles where increasing the pH is needed, bicarbonate can be added with a brewing salt.

• Brewing water - Most tap waters contain less than 150 mg/L of bicarbonate, although higher levels up to 400 mg/L are also common.
• Salt additives - Sodium bicarbonate can be used to add bicarbonate to the water if it is needed to increase pH. Calcium carbonate should not be used for this purpose because it is poorly soluble.

Effects of bicarbonate

In the context of brewing beer, bicarbonate has a vitally important effect on acid/base chemistry.

• Increased pH - Bicarbonate raises mash pH. This can be problematic, especially in pale beer styles. See Brewing pH.
• Mineral scale - When water containing both calcium and bicarbonate is heated, these ions react to form calcium carbonate, which precipitates as scale that can potentially accumulate on equipment. Although, this is less of a concern with stainless steel compared to mild steel.

How to adjust the bicarbonate level

For pale beers, the brewing water should ideally contain little or no bicarbonate alkalinity. While water with alkalinity can be used for brewing, the pH typically needs to be lowered by increasing the levels of calcium and/or by adding some form of acid while mashing (see brewing pH). Water purification using an reverse osmosis system is another way to remove the bicarbonate and other minerals in order to build an ideal mineral profile from scratch. Heating/boiling the water (with or without adding acid) can also remove some bicarbonate, but this is not a preferred method due to its moderate effectiveness, lack of consistency, and high energy consumption.

For darker colored beers, there is often a need for higher alkalinity to achieve proper mash pH. In this case, a sodium bicarbonate salt is a good way to increase the water's alkalinity. Bicarbonate salts should never be added to water used for sparging, because high pH during sparging will extract foul-tasting compounds from the grain.

See also

• Water
• Brewing pH
• Sodium bicarbonate