GEOLOGY OF BEER 79 The enjoyment of a glass of beer may be received by many senses: the sight may be attracted first by the clarity of a pale ale or the rich creamy head of a stout As the glass is raised to the lips the aroma of the bever age, possibly the bouquet of the essential oils of the hops, may excite the nostrils Then, as the liquid flows over the taste buds at the back of the mouth, and further volatile products diffuse into the back of the nose, the flavour of the beverage is perceived Finally, the beer enters the body, where the alcohol is rapidly absorbed into the bloodstream and exerts its well known physiological and psychological effects In more formal terms, in any particular brew the brewer is seeking a combination of five characteristics: flavour (including both taste and aroma), alcohol content, colour, head retention, and clarity The chemical nature of the water used in the brewing process exerts a strong control over all of these The Brewing Process There are several stages in the brewing process, and these are summarized below.The first stage is malting, which is the conversion of barley grains into fermentable malt The grains are steeped in water and spread out to germinate This initiates enzyme processes, which start to break down complex carbohydrates into sugars Kilning, heating to around 100 C, arrests these processes before they go to completion The malt is milled (ground) to form grist and then mixed (mashed) in a mashing vessel or tun with hot brewing water (liquor) Here the processes started during malting continue The liquor and malt (wort) are then boiled in the presence of hops, and bitter acids are extracted from them and converted into resins The wort is then cooled by water-powered coolers, at which time proteins and tannins separate from the hot resins Yeast is then added and fermentation takes place Fermentation adds fruitiness and fullness to the liquid and converts the sugars into alcohol Yeasts may ferment on the surface, something that is characteristic of most British brewing, or at the bottom of the fermentation vessel, as is more common in Europe A problem with top fermentation has always been the susceptibility of the yeast to breeding with wild airborne yeasts This often meant that brewing was difficult or impossible in the summer A solution was found by brewers in Europe in the late 1880s, who developed a yeast that sank to the bottom of the fermentation vessel Bottom fermentation is generally thought to produce a clean, soft, non-fruity beverage The Importance of Water Great volumes of water are involved in all stages of the brewing process, which is why so many breweries were originally sited near major rivers, though it will be a great relief to many to know that, despite suggestions to the contrary, river water was not necessarily used in the beer itself It is possible to brew beer anywhere, from any type of grain and water, but historically the classical area for brewing is the Beer Belt of Europe This belt essentially comprises six countries – Ireland, the UK, Belgium, Germany, the Czech Republic, and Slovakia – but also includes, to the south, parts of Austria (Vienna), Switzerland, and northern France and, to the north, the Netherlands, Denmark, and Sweden The greatest contribution to the chemistry of the brewing liquor comes from the brewing water, which forms a vital and integral part of the nature of the final product There are four anions that are particularly significant, of which Calcium is by far the most important It has three major effects It stabilizes the enzyme a-amylase and helps the breakdown of starch from the malt in the mash tun and in later processes It precipitates phosphate and thus increases the acidity of the wort, which is important because acidity influences the strength and character of the fermentation and the microbiological stability of the enzyme processes Lastly, it promotes flocculation (clumping together) of the yeast during fermentation Magnesium produces a sour to bitter taste, but retards phosphate precipitation, which in turn stops the required drop in pH level Sodium in small amounts gives a salty to sour taste, and potassium, whilst also contributing a salty flavour, can be particularly laxative above 10 ppm Although, as just described, it can be seen that the anions are important, it is really the cations that have the major influence, and this will be illustrated, first, using examples from the UK, before extending the logic to cover the rest of Europe Brewing in the UK Brewing was established in Burton-on-Trent in the English Midlands in the sixth century, when beer was brewed by the monks of the local abbey They drank beer rather than the more suspect river water The brewing waters at Burton-on-Trent (Table 1) are characteristically very high in sulphate (SO4), derived from the Triassic gypsiferous marls in the area Sulphate is very important for the brewing of bitter beers because it helps in the degradation of proteins and