Geology Of Beer

Chemical traces of beer have been found on fragments on a jar that’s more than 4,000 years old. In ancient Mesopotamia people using ingredients of poor quality to brew beer could be put to death. The Ancient Egyptians considered it to be an essential part of the afterlife. The gods of the Vikings loved it and still today beer is the preferred drink of geologists.

The quality of a beer depends on the quality of the used ingredients. One of the most important ingredients during the brewing process is water and geology strongly influences the chemistry and quality of water. Many breweries use private springs or water wells to satisfy their needs and even reference the supposed (often secret) water quality or purity in their advertisements. Natural water contains four elements especially important for the brewing process: calcium (Ca), magnesium (Mg), sodium (Na) and potassium (K). The concentration of these elements depends strongly on the geology of the catchment area and the source rocks of the springs or wells where the water is extracted.

In areas with water-soluble rocks like limestone, dolostone and gypsum the groundwater has a high concentration of calcium and magnesium. Calcium stabilizes the enzymes used by the yeast to break down starch and sugar into alcohol. This element also precipitates the in water naturally occurring phosphate, correcting the pH-value of the mash, an important factor controlling the microbial activity and alcohol production. Magnesium has similar effects, although too much magnesium can give the beer a bitter taste. Too high concentrations of sodium and potassium can also have an undesirable laxative effect on the heavy drinker. Other elements, like iron or zinc, can give the beer a strange metallic flavor or cause it to become cloudy. Sulfate (SO₄), deriving from evaporitic rocks and gypsum, can give the beer a desirable, slightly bitter flavor, by supporting the release of oils from hops and reacting with magnesium to produce magnesium sulfate
(Mg(HSO₄)₂, a bitter tasting salt. Also, water from springs with a high concentration of chloride and sodium from salt deposits can add a salty or even bitter flavor to a beer. However, in the correct proportions, the sweetness of the chloride ion prevails, resulting in the taste of a classic ale.

Adding gypsum (Ca[SO₄]·2H₂O) to water is still known as „Burtonisation“ after the city of Burton-upon-Trent, northwest of London, England, where in the 19th century more than 30 breweries used the springs and wells located in limestone and gypsum rocks for their beer.

By contrast, regions with sandstone-formations or metamorphic rocks are characterized by water with a low concentration of dissolved minerals. The lack of the previously mentioned elements in the brewing process results often in a beer with a less distinct flavor. To compensate for this disadvantage, the beer has to ferment for a longer time – preferably in a dark, cool environment, like a lava-cave. The name for Pils or Lager – classic beers from Central Europe – derives from the many caves found there in ancient lava flows and used as „Lager“ (storage room) for the beer.

Nowadays, many breweries import their water from elsewhere or even use customized water. Thanks to special membranes undesired elements are filtered out from the natural water and elements are added as the brewmaster desires. This technology guarantees a tasty beer, but sadly for the geologist, the geological secrets behind a pint of beer are lost forever.

Used literature:

CRIBB, S.J. (2005): Geology of Beer. In: Selley, R.C.; Cocks, L.R.M. & Plimer, I.R., Encyclopedia of Geology. Elsevier Academic Press: 78-81