Learn the science behind:
Brewing beer at home or in little breweries has become a lot more popular over the past few years. And long before that became a rage, monastries all over Europe has their own (small) breweries, some of which still brew today (e.g. the Trappists).
There are a lot of kits available nowadays for everyone to give beer brewing a shot. So that’s exactly what we did as well, we decided to brew our own beer! It proved to be fun and pretty easy to do, although it’s hard to get the beer to taste as good as store bought, I guess we need some more practice.
While brewing and reading about beer, I realized this beer brewing process is a great concoction of the different food science disicplines! So I decided to do a deep dive and take you all the way through this fascinating process.
Beer brewing process step 0: Ingredients – The kit
For our brew, we did get a little help, we didn’t have to start from the ground up, instead we used a kit from the Brooklyn Brewshop. In the Netherlands these can be bought through the HEMA. It contained the three essential ingredients to get started with beer brewing, the same big and small breweries will need at least:
- Grains: lucky thing, the grains are important for the final taste of your product, they’ve been pre-selected and packed for us. You can’t just use any type of grain, these grains might have received some sort of a treatment already, such as malting, to give you that great beer.
- Hops: for the flavour and aromas
- Yeast: without yeast, no beer, this is where the magic happens
Step 1: Mashing – Chemistry at work
The beer brewing process starts by heating and soaking the grains. For our little kit we had to place the grains in water just under 70°C for one hour. This temperature of 70°C is very important. To understand why, let’s first discuss what happens during mashing.
During mashing the grains soak in water, this first of all hydrates the grains. The grains can absorb and take up water. Furthermore, soluble sugars and starches will dissolve in the water and leak out of the grains. Last but not least, enzymes are at work during mashing, they convert starches from the grain into smaller, fermentable sugars. As you will see later, the yeast will initiate fermentation in the beer. However, yeasts often cannot grow from starches, they need readily available sugars. These are made by the enzymes.
As you might have read in my post on enzymes, enzymes have an optimum ‘working’ temperature. For the enzymes which is at work here, this temperature lies just below 70°C. If the mix becomes too cold during mashing, the speed of the enzymes will go down, thus less conversions take place. If, however, the temperature becomes too high, the enzymes will become disfunctional, thus nothing will happen anymore.
In more advanced mashing processes, the mixture may be held at various temperatures in a row. Each temperature will be the optimum temperature for a different enzyme. This could for instance be enzymes breaking down proteins. By heating up the mash a little more in every step, a different enzyme can do its job one after the other.
Mashing is ended in our case by heating the mix to a little over 70°C. That stops the enzymes from working.
Step 2: Sparging – Rinsing
Once the mash has been finished we have to get hold of the sugars we’ve extracted and converted. This is done by splitting the grains from the water by pouring it through a sieve. As a next step additional water is poured over the grains together with the already collected water. By pouring water over the mashed grains, sugars that may have been left behind can be rinsed off as well.
After this process the grains can be discarded. They have done their job and given off the nutrients required for further brewing.
Step 3: Boiling – extraction & flavour
After you’ve extracted all your sugars from the grain it is time to add some flavour and increase the concentration of your liquid. This part of the beer brewing process is the boiling phase, during which you boil the water that you’ve obtained during sparging. The water will evaporate and the concentration of sugars rises .
During the boiling phase hops are added, the second ingredient of our kit. Hops are the flower of the hop plant which give beer its characteristic flavour. Bitterness for instance generally comes from the hop. There are a lot of different hops and each beer has their own hop.
Commonly not all hops are added at once. The boiling phase takes about one hour when doing it at home during which hops are added at the start, after 45, 15 and 5 minutes and another portion at the end.
There is a good reason for not adding all the hops at once, all have a different function. Hops which are boiled for a long amount of time, thus added at the start of the boil give the beer bitterness. The prolonged heat causes chemical reactions in the hop which give bitter components. Hops which give the beer its aroma have to be added towards the end. If they would be added at the start all aromas would disappear. When is the best moment to add hops strongly depends on the beer.
Step 4: Cooling down & fermentation
After the boiling phase the beer is ready to start fermenting. During fermentation yeasts transform the sugars into alcohol. During this chemical reaction carbon dioxide is formed as well. Therefore fermentation should never take place in a fully closed container, the pressure will build up significantly. In home style brewing, simple water locks are used to allow gas to escape without letting anything come in.
Fermentation starts once the yeast has been added to the boiled down liquid. Yeast however is very temperature sensitive. If yeast is added at a too high a temperature is will be killed. Therefore the liquid is always cooled down to 20-30°C (depends on the type of yeast used) before adding the yeast.
Once the yeast has been added the liquid should be kept at a warm place. If it’s kept in the fridge for instance chances are the yeast will only grow very slowly, thus it will take very long for the fermentation to end. If, however, the temperature is around 20°C, the yeast will grow faster and ferment faster. Again though, the ideal temperature depends on the beer type and the yeast used.
Step 5: Bottling & 2nd fermentation
The first fermentation is commonly done in large tanks or buckets. Once the yeast has consumed all the sugars it will have ended. Now is the time to bottle the beer.
Bottled beer contains carbon dioxide. You notice this when opening your beer, some foam rises out or the foam will rise out while pouring your drink. There are two ways to get this carbon dioxide in a bottle. The first is siple injection of carbon dioxide which is commonly used in large scale factories. The other is to let yeast make some more gas and alcohol. This second fermentation can be initiated by adding some new sugars, for instance honey, to the beer just before bottling. The yeast will ferment again, producing gas. Since the bottle is only opened again when the beer will be drunk, the gas will remain inside.
While writing this post I ran into a very detailed description of brewing beer at home, suited for those wanting to make their own beer from scratch. Also, the Brooklynbrewshop provides very good, easy to understand instructions for making beer with their kits.