It never ceases to amaze me the multitude of different colours, flavours and alcohol content that brewers can achieve with four basic ingredients – malted grain, yeast, hops and water.
- Malted grains – Wheat or barley are allowed to germinate. Germination changes the starches in the grain to sugars. Germination is then halted by plunging the grain into hot water. This washes out the sugars and forms the wort.
- Yeast – this is a fungus, a micro-organism. It feeds on sugar and multiplies in the wort and produces ethanol (alcohol). The yeast will continue to multiply until all the sugar has been consumed.
- Hops – The flowers of the hop vine grow wild in British hedgerows and are cultivated in hop gardens. They add bitterness to the wort and aroma to the final beer. They inhibit the growth of bacteria hops also help to preserve the beer. In the 19th century India Pale Ale (IPA) was double or triple hopped to preserve it for the long sea voyage to India and other colonial countries.
- Water – Hard water is best for brewing beer. Hardness is defined by the amount of calcium and magnesium in the water. Hard water has a lot of these minerals dissolved in it. A brewer needs to know the mineral composition of the water and the effect this will have on the wort and beer pH.
Colour – The Standard Reference Measurement or SRM is generally used to measure the darkness of the beer or wort. A small sample of the brew is placed in a tiny vessel inside a device called a photometer and a measurement is taken of the strength of light of a particular wavelength passing through the beer or wort. The colour of the beer can vary from a pale lager through red to an Imperial stout.
Beer Strength – In the UK it is recorded as the amount of Alcohol By Volume (ABV) expressed as a percentage. This is the amount of ethanol (aka alcohol) in 100ml of beer represented as a percentage e.g. 4.2% means 4.2ml of alcohol in every 100ml.
Traditionally ‘X’ was used to mark beer strength. It might have been used by medieval monks to mark casks of particular quality. It could also have it’s roots in duty taxes which were introduced in 1643. ‘X’ marked casks of higher strength beers for which the brewer had to pay 10 shillings extra tax per barrel. Later brewers added superfluous ‘X’s to indicate progressively stronger beers. It is now simply a trade mark used by a number of breweries in the UK, the Commonwealth and USA.
Today, in order to calculate the beer strength, modern brewers need to estimate, as accurately as possible, the density of the wort and then the density of the final fermented brew. The difference between these two readings is the amount of sugar that has been converted to alcohol by the yeast. A hydrometer is used to measure the density which is better known as the Specific Gravity (SG). The more the yeast converts the sugar in the wort to alcohol the bigger the difference in the two results will be and the greater the strength of the beer.
Very small amounts of other ingredients may also be used. Isinglass, for example, which is a gelatin produced from dried fish swim bladders is used to accelerate clarification of beer. This odourless and tasteless product helps yeast suspended in the brew to settle out producing a clear, bright beer.