At the end of the sparge we have collected what brewers call ‘sweet wort’. We now need to boil the sweet wort and there are a variety of reasons for this:
– It will sterilise and concentrate the wort.
– It will precipitate haze causing proteins out of the wort
However, the primary reason for boiling is to extract hop bitterness, hop aroma and hop flavour. The longer the hops are in the boil, the more bitter components are extracted, so bittering hops are added at the start of the boil. Hop aroma and flavour are achieved by extracting the essential oil from the hops, these are quite volatile and are lost in a long boil so flavour and aroma additions are made at the later stages of the boil. Boiling generally takes about 1 hour.