BOILING
WHY BOIL ?!
- Never under estimate the importance of the boil ! An awful lot happens during the boil and much of it is hidden from the human eye. Just because you can't see it doesn't mean it ain't happening !
- For starters, unless you've been impeccable about your mash-out step, there are still likely to be some enzymes floating around in the wort and these will do their best to nibble away at the fermentables you've created. So boiling brings their short existence to a rather violent end.
- Boiling also sees much of the proteins and odd sounding chaps called polyphenols, all derived from the mashing step, being forced to precipitate (come out of solution) and then coagulate (stick together). These chemical compounds, if left dissolved in your wort, would create havoc with hazy beer further down the line. During the boil, many of these compounds come out of solution and in fact can be seen floating around the otherwise clear wort, looking a lot like cotton wool. The matter that "breaks out of solution" during the boiling step is called the "hot break" and the boil, if vigorous enough, will see these compounds stick together with sufficient integrity that, at boil end, they can happily sink to the bottom of the boiler. So a vigorous boil is required !!
- The boil also kills off any bacteria that may have been lurking in your wort up to this point. This is especially important because, other than "kitchen style cleanliness", the processes before the boil can be carried out free from sterilisers etc. Its only after the boil that sterilisation becomes so critical.
- The hops are added during the boil and, depending on when in the boil they are added, they can contribute aroma, flavour or bitterness qualities. This process is again chemical in nature and a nice rolling boil accentuates the boil's ability to get the reactions going.
- Finally, of the more basic things achieved during the boil, loss of liquid through evaporation will see the wort volume decrease and hence the density of the wort increase. Your recipe should take all of these issues into account so that, at boil end, you have the required original gravity of the beer.
WHAT ABOUT THE HOPS ?!
- Bring your wort to the boil, being careful not to boil over ! To prevent boil-overs, add your bittering hops just before the boils starts, it stops all that frothing around ! Others say chuck in ice cubes for the same effect ! Whatever you do though, don't cover your boiler as the wort reaches boiling temperatures because this sends out a nice loud message to the wort that it is now permitted to blow the cover off and crawl all over the surroundingg area. Everyone does it at least once. Some have more experience !
- Now, for how long should you boil those hops ?! Well, it all depends on what you're trying to achieve in your finished beer. Should it be very aromatic ?! Full of hop flavour ?! Very bitter ?! To achieve these attributes of the finished beer you need to juggle the boil time and obviously the amount you add. Go check out a bitterness calculation in a spreadsheet if you need assistance. Hop bitterness levels aren't usually the sort of thing you calculate by hand when there are loads of additions of varying masses. However, it can be done so here's a page from our homebrew club's technical articles : Calculating Hop Bitterness Levels
- To get a handle on the various effects though, check out the following graph. It shows the time from the beginning of the boil (on the horizontal axis) and the percentage of the various attributes that you can expect to achieve for that boil time (on the vertical axis).
- The graph shows three things :-
- If you add a measured amount of hops into the boiler, it takes just a few minutes before the hop aroma profile in the finished beer would sink to zero.
- The flavour of the hops in the wort maximises after about 15 minutes of boiling but by around 45 minutes is dropping off rapidly
- The bitterness contributed by the hops to the wort increases throughout the boil, its mostly there after 60 minutes but still climbs a little up to 90 minutes.
- The lessons here are :-
- If you want good hop aroma, add the "aroma hops" in the last 0 to 2 minutes of the boil.
- If you want good hop flavour in your beer add the "flavour hops" in the last 15-45 minutes of the boil.
- If you want good bitterness levels in your beer the "bittering hops" should be boiled for a full 90 minutes.
- The exact amount of each hop to add depends on its chemical properties. Of most importance for homebrewers is the bitterness level as expressed as the "alpha acid" level. I would strongly suggest not buying hops that don't have the alpha acid value listed. Some people use crop averages but these swing hugely year to year and farm to farm . . . so don't compromise, find a supplier who can give you the alpha acid level of your hop. A supplier who can do this is also likely someone who knows something about its importance . . . all too many suppliers try to persuade you to compromise your position. Stick to your guns. I mainly buy through the professional brewing trade in this country (South Africa).
- The alpha acid level simply tells you how bitter the hop is. To get a specified amount of bitterness in your beer you need to use the hop calculator in the spreadsheet on the download page, enter the mass of hops, its alpha acid level and how long you boil it for. All of these can be seen from the above graph to influence the bitterness of the beer. Recipes often tell you how bitter the beer should be. Use the calculator to come close.
- As a basic plan I usually start at the end and work backwards. Do I want hop aroma ?! Yes . . . then plan say 5 g of good quality aroma hops (in a 23 litre batch) in the last 0-2 minutes of the boil. This adds pretty much zero bitterness compared to the 90 minute boil version.
- Do I want lots of hop flavour ?! Yes . . . . add some hops in the last 15-20 minutes of the boil. Restrict the overall addition here as you could over power your hop flavour. Add say 10 g of a good flavour hop.
- And of course I need hop bitterness. Just set the time to 90 minutes, edit the alpha acid level and tweak the mass until you get the bitterness level that you want.
- If I'm using high alpha acid bittering hops in order to save on hops, I often add two different hop varieties for the bittering step, adjusting the relative masses so that they each contribute the same amount of bitterness. The lower alpha acid hop would therefore be added in a larger quantity at this stage than the high alpha acid hop.
Right, so you're sorted out on the hops ?!
