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Mads Bonde

2 min read

You may have heard the buzzword flying around: Do-It-Yourself Biology. But what does it mean? Is it a movement reserved for self-proclaimed biology “geeks” playing with test tubes in their basements? The truth is, although DIY bio seems to be a new thing, forms of the practice have actually been around for hundreds of years…we’re talking about homebrewing beer!

In this post we asked Mikkel, one of our biotech project managers and accomplished home brewer, to introduce us to the art of brewing beer at home using simple and cheap instruments. If you’ve ever thought about dabbling in homebrewing, this holiday season might just be the time to brew up some tasty Christmas beer. Below, Mikkel gives us the science behind the art of homebrewing.

Mikkel on Homebrewing

The process of brewing beer is fairly simple. Basically, brewing beer uses yeast’s ability to produce alcohol from sugar, when there is little to no oxygen available. The yeast used is the same as in baking, also known as bakers yeast (saccaromyces cerevisiae). However, the yeast for brewing beer has been changed somewhat to allow for higher alcohol tolerance for example or has been chosen because of its ability to produce taste variations, for example nutty or berry flavours.

For the yeast to grow and produce alcohol it needs something to eat. The main food source is sugar, which is provided by malt. Malt is barley that has been heated and allowed to sprout. In this process the sugars in the seeds become available and the seeds produce enzymes needed in the brewing process.

On the brewing day, the first thing to do is to heat water to approximately 70 degrees Celsius, depending on the specific recipe followed. Then the required amount of malt is poured in to the water, which causes the temperature to be lowered. This substance is called the mash and will be left for approximately one and a half hours. During this time, the sugars in the malt are extracted and so are the enzymes. The latter will cleave the sugars to short chain sugars, mostly maltose which will be converted to alcohol by the yeast.

When having extracted as much sugar as possible, the mash is poured into a bucket and the malt is removed by sieving. The resulting liquid is called the wort and is poured back into the pot and boiled for an hour. As soon as the wort starts to boil, bittering hops are added. This gives the beer its bitter taste. After 30 – 45 minutes of boiling, taste and aroma hops are added, respectively. Different varieties of hops can be used for different flavouring. There are many different hops to choose from so experimenting with this can change the beer significantly.

After an hour of boiling, the wort needs to be cooled to 25 degrees Celsius before adding the yeast. So, for example, if you have a 20 liter batch it can take a day or so to cool down if just left on the stove. Therefore, it’s helpful to use a very handy tool called a chiller, which is a long copper pipe connected to the water hose and lowered into the wort. By running cold water through the chiller, heat is removed from the water fast. Not only does this save you precious time, but it also decreases the risk of having bacterial infection in your beer, which may give an awful and sour taste. When the wort has been cooled, it is important to use only sanitized equipment. Otherwise there is a big risk of infection.

Once the temperature has been lowered to 25 degrees Celsius, the wort is poured into your fermentation bucket and the yeast is added. During fermentation in the closed bucket, CO2 is produced and has to get out of the bucket. An airlock placed in the lid of the bucket will allow a CO2 exchange with the surroundings, but not let O2 into the bucket (which would ruin fermentation!).

The fermentation bucket is left to ferment for a week or two and when the density of the beer has reached around 1010 you are ready to pour the beer into your sanitized bottles. Before then you’ll want to add some sugar to the beer to allow for carbonation. Depending on the type of beer approximately 7 g of boiled table sugar is used pr liter of beer. Let the beer ferment for a week or two in the bottles to produce CO2.

Ready to DIY? Try this recipe for Christmas Beer.

Enjoy your beer!


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