Science Behind Beer

Despite the poor weather this bank holiday weekend in England, Wales and Northern Ireland, plenty of residents from the UK are likely to be looking forward to a weekend of sleep and general relaxation. It’s known that alcohol consumption increases during longer weekends but do we understand the science behind one of our favourite pastimes?

The National Geographic dubbed it our 9,000 year love affair with alcohol. It appears that from the dawn of civilisation, we have been making alcohol. beerChemical analysis shows that the Chinese were making a type of wine from rice, honey and fruit 9,000 years ago. Alcohol is so popular that at the University of Munich in Germany, you can actually get a degree in brewing science. The lab where this is possible is alongside the Weihenstephan brewery, founded by monks 1040 A.D. and is the oldest continuously functioning brewery in the world. So what is the science of brewing beer?

The main ingredients of all beers are water, malted grains, hops, and yeast. It is the combination and process themselves which alter and thus produce different results. The general process is as follows: 1) milling – dried barley is added and ground, 2) mashing – water is added to produce wort (a sugar-rich liquid), 3) brewing – hops and any other ingredients are added and the mixture boiled, 4) cooling – the mixture is cooled to 10-20oC, 5) fermenting – yeast is added, and the sugars are converted to alcohol as the mixture ferments, and 6) maturing – mixture is left to mature, filtered and bottled. It is the chemicals produced during the brewing process which give beer its flavour and bitterness.

What causes these different flavours? The bitterness of beer is due to the hops used. Hops contain alpha and beta acids, and during the brewing process these acids are degraded, contributing to the bitter taste which is characteristic for beer. Hops have various combinations of these acids and are chosen based on how bitter the brewer desires the final product to be. Beta acids make a more bitter beer than alpha acids because they take longer to degrade and are therefore fermented for longer.

hopsThe varying flavours also come from the hops but this time it is caused by essential oils found within them. There are over 250 essential oils which have been identified from hops. Esters are the last contributors to a beer’s taste and smell. A light lager will have minimal esters concentrations, whereas a hearty ale will have much more. Esters form as a by-product of alcohol production, enhancing taste. Acids in the hops react with the alcohol produced during fermentation, and with a little help from an enzyme in the hop (i.e. acteyl coenzyme), esters are made.

Ever wondered why beer is kept in opaque bottles? The alpha and beta acids in the hops are antiseptics, meaning they prevent bacterial growth, prolonging shelf-life of the beers and enhancing the growth of yeast during fermentation. However, when the alpha acids degrade they form iso-acids, which can react with light and a chemical in the malt, producing unpleasant tastes. beer bottleWhen this happens the beer is known as ‘lightstruck’, and to prevent this, beer is stored in opaque or dark glass so it cannot react with light. This is the same for prescription drugs kept in dark/opaque containers. It is done to stop them from reacting with/degrading in the light.

The strongest naturally fermented beer (in 2015) was ‘Samuel Adams Utopias’ at 29% alcohol, created by the US brewer Samuel Adams. However, the strongest fortified beer (i.e. when pure alcohol, such as ethanol, is added to the process) was created by Scottish brewery, Brewmeister. It is called ‘Snake Venom‘ and has an alcohol percentage of 67.5%. Beer isn’t for everyone. Generally speaking, when compared to wines and spirits, beer is relatively weak. Gin, for example, is made by a completely different process which involves distilling pure alcohol (such as methanol) over juniper berries, producing an alcohol percentage of at least 37.5% (to be considered a gin in the UK). Overall you can see that the production of beer is more complicated than possibly first assumed. Next time you enjoy your favourite hoppy beverage, remember how much science went into making it.

Here is a great link to a site I love Compound Interest, with a more in depth explanation of brewing beer and the chemistry behind it.

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