Boil questions

[Beer_Matt]

Hi, I've got some AG brews under my belt now but was wondering what is the purpose of the boil, is it for bitter des/aroma extraction from the hops? Pasteurisation? Can I reduce boil time to 60 mins? Lid on or off and why?

Thanks!

Matt.

[lord groan]

As far as I can tell there are several reasons for boiling:
DMS removal - "Dimethyl sulfide (DMS) is created whenever wort is heated, by the breakdown of precursors found in pale malts. DMS is present in most beers at some level. It is excessive DMS that gives some home brewed ales a "cooked corn" character.Under ordinary circumstances, most of the DMS that is created by heat is then evaporated during the boil. Some DMS is also removed during vigorous ale fermentations, which is why higher levels are often found in lagers. "
(Not my own knowledge, copied from elsewhere)

Sterilisation of the wort

Extraction of bitterness from hops

Reducing wort volume to get required original gravity

There may well be other reasons too!

I believe homebrewers in the US often boil for 60 minutes ( waits for the sound of angry HB'ers to shoot me down) rather than the UK's 90 minutes, so yes you can reduce boil time but you'll need to reconsider how much water you use for sparging because reduced boil means reduced evaporation which will leave your wort with a greater volume and therefore a lower OG. Also hop quantities may need adjusting to get required bitterness if boiling for less time
Lid on - keeps the DMS from evaporating, stops volume of wort from reducing
Lid off - allows DMS to evaporate, lets wort volume reduce to get desired OG.
So its your choice - I think lid off for 15-20 minutes of vigorous boil gets rid of the DMS, after that you're just controlling evaporation

[Martin G]

There are also some flavours added by the action of heat on the sugar, sort equivalent to browning of a cake in the oven. Not 100% how significant or important these reactions are to be honest and have planned to experiment a bit eg. 80C heat with a mechanical agitator for the hops, never got around to it though!

[Matt12398]

A vigour boil is also required for the hot break which coagulates the proteins in the wort which helps to remove them, creates clearer beer and helps with beer stability therefore increasing the shelf life.

You also get the cold break on the crash cool.

[Uncle Joshua]

I now do mainly 60 minute boil. I also mash for between 60 and 75 minutes.

[Martin G]

A vigour boil is also required for the hot break which coagulates the proteins in the wort which helps to remove them, creates clearer beer and helps with beer stability therefore increasing the shelf life.

You also get the cold break on the crash cool.

I'm sure I read the mention of proteins earlier in the thread, I must be going mad.

[fisherman]

I used to boil for 90 mins. Now I mash for 90min but boil for 60 mins and I cannot tell the difference. I'm sure it is the timing of when you add the hops that makes great hoppy tastes. Also in my 60 litre boiler it is a good rolling boil not just a simmer that gets a good hot break.
Happy brewing all..

[Beer_Matt]

Thanks all, some good info here.