What's the boil for?

merc230ce

Am I right in thinking that the reason you boil (in Extract brewing) is to get the oils out of the hops? There seems to be no benefit to boiling malt extract, and in fact it can just be added at the end. Just trying to figure out why Kit brews don't require boiling but all other methods do, even when the ingredients are the same.

(Apologies for the question, but it's never enough for me to know the 'How', I always like to understand the 'Why' of a thing!)

slayerking

Kits dont require boiling because thats been all done for you by the kit makers!

Theres a couple of things that the boil does. Heres a few:

The main thing, which you have pretty much, is that the boil allows the hop oils to isomerise, which causes them to be soluble in wort and creates that bitter flavour we love in beer!
The boil also achieves something called hot break which causes proteins to coagulate making them more likely to fall out of solution during the chilling period. This will mean you will have a healthier wort and a clearer end beer.
A full boil also steralizes the wort, leaving it nice and clean, free from nasties for the yeast to enjoy.
If doing a full boil from an all-grain beer, the boil stops the enzymes from the mashing period.
Malt can have some level of Dimethyl sulphide (DMS), which is formed during the boil, and is driven off in the evaporation.

There might be a few more reasons, there the main ones I think.

rubadub

Boiling up a kit will make it dissolve better, if you just dump syrup into a fermenter full of hot water it can take a lot of stirring to dissolve it all, if you dump boiling water into a fermenter it will drop temp very quickly as the fermenter absorbs it, some is lost just to air while pouring too.

If not stirred/dissolved enough you can have a syrup on the bottom and weak solution on top.