Beer/Brewing 101 The Boil and Beyond
Previous posts in this series:
Intro
Ingredients
The Brewing Process
Malting and Mashing
Now that the mash is completed and we have our wort, sugary and malty liquid, in the kettle it’s time to start the boil. There are two main reasons for boiling the wort. One is isomerise alpha acids from the hops to produce the bitterness in the beer. The other main reason is to sanitise the wort. At this point in the brewing process there will be all kinds of wild yeast and other bugs hanging around. We boil, typically, for 60-90 minutes killing as good as all bugs that are present. There are other effects and benefits from the boil but these are the primary reason it is performed.
The typical boil is 60 to 90 minutes. It is generally considered that 60 minutes is enough time to effectively kill any wild yeast or other bugs that are in the beer. Boils can be extended out to 90 minutes and in some cases beyond to produce specific flavours in beer. Some people will call the flavours produced by a longer boil as caramel type flavours. Although the flavours are similar no caramelisation will take place in the boil. The boil just doesn’t get hot enough. However, maillard reactions will happen that can give caramel like flavours. It’s beyond the scope of this piece to go into maillard reactions and their difference to caramelisation but it’s easy to find info on Google if you want to dig deeper.
Hops can be added at a number of times during the boil. In general hops that are added at the start of the boil, with 60-90 minutes to go, are for adding bitterness to beer. These will generally be a variety with high alpha acids and with little regard to flavour and aroma. This does vary with style but is a good general rule. Hops added between the 20-40 minutes remaining in the boil mark are generally considered flavour additions. The earlier in a boil hops are added the more alpha acid you get for bitterness but you also boil off more of the oils that produce flavour and aroma. Hops added in the last 15 minutes of the boil are considered aroma additions. The hops chosen for flavour and aroma additions will be chosen based on those characteristics of the hops and will generally have little regard for the bittering qualities.
In some beers, common in IPA and American style pale ales, hops will be added at the completion of the boil. These hops will contribute very little to bitterness but can have a large impact on the aroma and flavour of the beer. The wort takes some time to cool so the hops will have the chance to add flavour and aroma.
At the end of the boil the wort will normally be whirlpooled. This can happen in the main kettle or after transfer to another special whirlpool vessel. The whirlpool is exactly what it sounds like and it is done to remove hops and other debris from the wort. After whirlpooling the matter will generally be in a clump in the centre of the kettle and clean wort can be extracted from the outside. There are some breweries that use other methods instead of or in combination with whirlpooling like filters but whirlpooling is common to most breweries.
Once we have extracted the hops and other debris from the wort we need to get it chilled as quickly as possible. Between the end of the boil and when the yeast is pitched the wort is very susceptible to infection so you want to get it cool and have the yeast pitched as quickly as possible. The temperature the wort will be chilled to depends on the style of beer being produced. Typically for an ale you will chill to about 18C and around 10C for a lager but there is a lot of variation for different beers. Most commercial breweries use some form of counter flow chiller normally in the form of a plate chiller. The basic theory is that hot wort enters pipe at one end. Around that pipe is a jacket that has chilled water flowing in the opposite direction. Once the wort exits the pipe at the other end the chilled jacket has reduced it’s temperature to the required pitching temperature. There are a number of other methods used but some variation of this is the most common.
The chilled wort will be transferred via the chiller into the fermenter to have the yeast pitched and to begin fermentation. At this point extra oxygen may also be added to the beer but we will cover fermentation in more depth in the next post. Don’t forget to check out How to Brew by John Palmer it’s my main source for brewing information.
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