Brewing

Brewing is defined as 'the combined processes preparing beverages from the infusion of sound grains that have undergone sprouting, and the subsequent fermentation of the sugary solution produced, by yeast - whereby a proportion of the carbohydrate is converted to ethanol and carbon dioxide'.

Malting

The aim of malting is to transform and mobilise the food stores of the cereal grain (barley germination). The barley is moistened and sprouted in a controlled manner. Enzyme activation results in the conversion of carbohydrate stores (starch) to readily available sugars.

Kilning

Traditional malts usually involve kilning. The germinated grain (sometimes called the green malt) is taken to a kiln and dried using warm air. Care must be taken to dry the malt quickly but not too quickly as this will result in a loss of enzymes produced during malting.

Milling and Mashing

There are two ways by which milling can be achieved, dry or wet. In dry conditions the kilned grain is cracked open by passing between two sets of rollers. The grain is crushed by the first set of rollers, with the second set producing even finer grits and flours. During wet milling grains are soaked in water in a steeping hopper (see picture). The damp malt is then crushed by rollers and the slurry produced mixed with water and passed straight to the mash tun.

Mashing is the process of mixing ground malt with brewing liquor (water). The temperature, pH and  mineral content of the water used in mashing greatly effects the properties of the final beer. Put simply, mashing involves a vessel, the mash tun, within which the ground malt and water are mixed. The mash is then allowed to stand for a set period of time with the resultant sugary liquid, called wort, being removed. The removal of wort is called sparging. Given yeast this fermentable extract will produce beer.

Boiling and Chilling

The wort is boiled for at least an hour with hops being added continually. There are nine aims of wort boiling - sterilisation, termination of enzyme activity, concentration build-up by evaporation, completion of chemical reactions, coagulation of proteins, decomposition of unwanted volatile components, bittering due to hops, colour enhancement and extraction of essential oils and polyphenols from the hops. Wort is chilled using a heat exchanger and then aerated before being transferred to the fermenter.

 Fermentation

Yeast is mixed with wort in the fermenter. There is a readily available supply of sugar from the wort which the yeast use to grow and reproduce exponentially. Having used all of the available oxygen yeast is forced to respire anaerobically. This produces ethanol. Eventually ethanol concentrations become so high that it become toxic to yeast growth.

Maturation

Following all of the above processes the beer is stored and allowed to mature. This may improve the flavour and appearance of the beer. Often the beer is then filtered before carbonation and packaging.