A Beginner’s Guide to the Science of Brewing
I'm often surprised by how many of my beer-obsessed friends don't spend more time contemplating how brewers turn a concoction of malt, hops, yeast and water into that liquid that we often over-indulge in. Many brewers would agree that knowing the science of brewing is important to the process of brewing beer, so shouldn’t it be just as important for the process of drinking it too?
The idea behind this website, Science Made Beerable, was to reveal the science behind beer that is all too often forgotten about. It’s a hopportunity for us to waffle on about Nordic yeast strains and the impacts that hop-growing conditions has on flavour. But for these blog posts to make sense, I felt like I had to provide an introductory blog that explained the very basics of brewing science. So here it is - a beginner’s guide to the science of brewing!
The first thing we need to create beer is a sugar supply to drive the fermentation process (the yeast needs something to eat and produce alcohol from – but more about that later). However, unlike fruit-based alcohol like wine or cider which contains natural sugars, there are very little fermentable sugars in the grain used in beer. This is the first way of many in which beer is different to wine - beer is brewed. Brewing is the process of converting starches into fermentable sugars, which are then fermented into an alcoholic beverage.
Grains, the seeds of plants in the grass family, contain starches that provide energy for the developing plant. As the seed germinates, or sprouts, it produces enzymes that convert these starches into sugar. Barley is particularly good at producing these starch-transforming enzymes. While brewers now understand that with the right treatment the seed will produce the enzymes itself, it did take us a while to work this out. When brewing ‘chicha’, a maize beer, Inca women would chew the grain, breaking down the starch with the enzyme amylase in their saliva.
Nowadays, the process is far less gross and begins by soaking the seeds in water, tricking the barley into thinking that it’s time to germinate. This causes those starch-unlocking enzymes to develop inside the seed. However, we want those starches and sugars for our beer, so the seeds are dried out and heated in a kiln to stop the seed from sprouting. The finished result is a malted grain known as pale malt which is now ready for brewing!
There are also a range of speciality malts that are used to create different beer styles and flavour profiles. These malts are created by roasting the grains to a higher temperature and longer heating times, creating darker and tastier malts. The browning or toasting of these malts occurs via Maillard reactions between sugars and amino acids in the grain which bring out the toasty flavour of the malt. This leads to flavours such as caramel, chocolate and coffee, which are typically found in the darker style beers, like amber ales and stouts.
Now that we’ve got the malt, the brewer can now begin brewing beer and it all begins with a process known as mashing. The roasted malt is initially crushed to grist (a course powder) and placed with into a large vessel, known as a mash tun, with warm water. During this step, the enzymes that were produced during the malting process are activated and they convert the remaining starches into sugars. The goal of this process is to break down the large starch molecules into sugars that can be digested by yeast.
The water and grains are typically left to rest for around 60 minutes somewhere between 60-70°C (of course, this varies on the style and aim of the beer). After this, the grains are separated from the water, leaving a sweet, malty liquid known as the wort. The brewer then rinses the grains in a process known as sparging, collecting the remaining fermentable liquid from the grain.
The quality of the water used during this process is important and can have huge impacts on the flavour of a beer (beer is mostly water after all). For example, the hard water (high mineral content) in Dublin is ideal for making stout, such as Guinness, whereas the water of Pilsen (where Pilsner originated) is very soft and free of minerals. Nowadays, brewers will modify the chemistry of the water by using additives to achieve the flavour and “mouthfeel” of the beer they want.
Once the brewer has their wort, they place it into a boil kettle where it's heated to a rolling boil. This is when the brewer adds those little nuggets of flavour - the hops. The flavour contribution of the hops will depend on when they're added to the boil. If they're added early on, they contribute bitterness to the beer, while hops added later on in the boil will provide aroma to the brew.
Hops are the flower or cone of the hop vine, which is part of the hemp family. The flavours and aromas in the hops come from small glands inside the flower buds which contain alpha acids, beta acids, oils and tannins. The proportions of these will vary among different varieties of hop, meaning that the strain of hop that is used in a beer can greatly impact the resulting flavour. Alpha acids provide bitterness, the oils provide aroma, while the tannins and beta acids hold important disinfectant qualities (which is why hops were added to beer in the first place, to prevent growth of unfavourable bacteria or fungus).
These hops often lead to the incredible variety of flavours we find in beer, such as citrus, pine, and stonefruit. However, the beer still has one more very important step before it's drinkable (honestly, it's still truly disgusting at this stage).
Finally, after chilling and aerating the wort, it's time to add those microscopic fungi to start the fermentation process. Yes, just like the age-old saying, "brewers make wort, but yeast makes beer." From the perspective of the brewer (and the drinker), the purpose of the yeast is to consume the sugars in the wort and leave behind alcohol and carbon dioxide. But yeast does more than just make beer boozy and frothy, they also contribute to the flavour.
There are a wide range of yeast strains that a brewer can choose from. Due to variations in metabolism, different yeast strains produce unique by-products, such as esters, fusel alcohols and phenols, leaving the beer with a distinct flavour. A good example of this are the banana flavours often found in hefeweizens which are caused from an ester called isoamyl acetate produced by the unique yeast strain that is used.
Generally, there are two main styles of yeast used in brewing, top-fermenting (ale yeast) and bottom-fermenting (lager yeast). Ale yeast (Saccharomyces cerevisiae, the same yeast used to make bread) likes warmer temperatures (15-25°C) and doesn't convert as many sugars into alcohol meaning that ales will often have a fruity aroma and flavour which comes, in part, from the residual sugars. Meanwhile, lager yeast (Saccharomyces pastorianus) produces a drier beer and enjoys the cooler temperatures (it’d be a big fan of the Tasmanian winters). This fondness for the cold evolved in the 15th century when Bavarian brewers would lager (store) the beers in large caves to keep them drinkable during the extensive hot summers.
If you’ve ever had a Lambic or farmhouse style beer, then you would have experienced Brettanomyces (and what an experience it is), the “wild cousin” of the Saccharomyces yeasts. This divisive third type of yeast produces very distinctive flavours of fruit, spice and tartness, which has been described by some as having the flavour of a “wet horse blanket” (which, I promise, isn’t as bad as it sounds).
Fermentation will usually take between 2-14 days for an ale, but a lager can take many months, afterwhich, the beer is conditioned. Conditioning is often performed in a pressurised tank to allow the beer to carbonate, either from the carbon dioxide produced by the yeast or by introducing pressurised carbon dioxide. This stage lets the beer mature, developing more balanced flavours and allowing larger proteins and yeast to fall out, resulting in a clearer beer (of course, in this age of haze this isn’t always the goal, but more on that in a later blog).
Conditioning can take from two to four weeks, but it really depends on the style of beer. Many breweries will now use fining and flavouring agents to speed up this process. Lagers are often aged in large tanks at near freezing temperatures for up to six months, which reduces the sulphur compounds produced by the yeast, resulting in a cleaner and tastier beer.
There you have it, the beer is now ready for the most important stage – consumption! Just four seemingly simple ingredients can create a broad range of diverse beers, and the resulting chemistry and flavours are exceptionally intricate. So next time you’re at your local drinking hole ordering a crisp, refreshing lager or a boozy, resinous IIPA, take a moment to consider the science behind that delicious golden liquid in your hands and thank those chemistry wizards and innovative artists that we call brewers.