Drygate: Brewery Science

Welcome to the Drygate brewery in Glasgow, Scotland. Beer has been brewed in Scotland for more than 5,000 years, and, at the site of a former box factory, Drygate is continuing this tradition.

Brewing beer is a complex scientific process that requires highly skilled workers. It involves a chemical process called anaerobic respiration that is important to all life. Let’s explore how it works.

Ethanol – C2H6O – is the chemical name for the alcohol found in drinks such as beer and wine. It is made when sugar in grains is converted by yeast into ethanol and carbon dioxide in a process called fermentation.

Humans have brewed beer for thousands of years. Beer has at many times been seen as the safest form of liquid, as the process of making it kills bacteria that can be found in milk and water. 

The dangers of drinking too much alcohol have led to laws whereby it is illegal to consume or buy alcohol before a certain age. 

Four basic ingredients are used to make beer: grain (usually barley), hops, yeast and water. Brewing beer involves extracting sugars from the barley that the yeast can turn into alcohol and carbon dioxide.

Yeast performs this function via an energy-producing process called anaerobic respiration – “anaerobic” means without air. Anaerobic respiration is used to some extent by most living things to produce energy, but when yeast is involved, alcohol is formed from the sugars.

Malting the barley is the first stage of making beer. This process involves germinating barley seeds by keeping them moist and warm. Germination activates enzymes in the grain that turns starch (which yeast cannot consume) into sugar (which it can). 

At a certain point, the barley seeds are dried at high temperatures in a kiln to prevent them germinating entirely. The malting process adds flavor that will contribute to the taste of the beer.

The malt is produced in Alloa, Scotland, and delivered in 25 kg sacks. Each sack will produce approximately 1 barrel of beer, containing 163 litres or around 300 pints.

There are many types of malt, differing in the kinds of barley and malting process used. Brewers select malts depending on the flavor and color they want. 

The brewing process involves combining the 4 ingredients of beer – water, malted barley, hops and yeast – in well-defined stages. These stages are the same for every kind of beer, wherever it is brewed.

What makes beers different is determined by individual brewers, who use their experience and expertise to adjust proportions, timings, temperatures and other factors to produce distinctive products.

The ground malt is put into a metal vessel called a mash tun, where it is heated with water. The starch from the malted barley is converted to sugars that dissolve in the water. This sweet solution is known as wort. 

Fermentation is the process through which the sugar (glucose in the malt) is converted by yeast into alcohol (ethanol). Fermentation is a kind of anaerobic respiration, which means it is carried out in the absence of air. 

If air were present, the reaction would be aerobic respiration.

The wort has to be cooled before yeast is added. When the yeast is added – or “pitched” – to the wort in the fermentation tank, fermentation begins. The yeast turns the sugars into alcohol and carbon dioxide. 

Yeast has been crucial in the history of civilization as an ingredient in bread making. The chemical equation for fermentation is exactly the same: the carbon dioxide produced helps make the bread fluffy, and the ethanol mostly evaporates in the oven.

The result of fermentation is an alcoholic beer. However, it’s still not ready to drink. For one thing, the beer is still uncarbonated or “flat”. 

The beer is stored for a few weeks or months, during which it becomes carbonated naturally via the carbon dioxide produced by the yeast. This also allows some of the flavors to develop. Finally, the beer is ready to be sold in shops and bars.

Beer is often stored in bottles, which are convenient to drink from. However, the taste of beer can be badly affected by light – particularly ultraviolet (UV) light. Brown glass is better at blocking ultraviolet than green or clear glass. 

Wooden barrels offer a similar storage environment to kegs – keeping light from reaching the beer – with the difference that the beer gets more flavor from the wood. New wood gives beer an unpleasant flavor. Instead, barrels previously containing whisky are used.

Kegs – airproof and sterile metal containers – are the most stable way to store beer. Additional carbon dioxide is added to fill the vacuum as the beer in a keg is used up, helping to ensure it doesn’t continue to ferment.