Russian Imperial Stout 2nd time round... Hop boil time

[Brewedout]

In February 2012 I made my first RIS after all of the talk that was going on in the forum, it caught my interest! (Thanks Aleman for the inspiration and pointers from your posts!). I based my first recipe on the bjcp style guidelines and I am very pleased with it, after 13 months it is lovely :grin:

This time round I am trying a different recipe, but note that some people have boiled hops for 120min instead of 90mins. There is little difference in Bitterness (IBU's), so what difference will this make to the flavour?

Thanks :thumb:

 

[BigYin]

Well, it'll make the OG higher for a start with the extra boil evaporation losses...

Continuing to boil a more concentrated wort may also begin to give caramel flavours? (that's a guess!)

You will get a bigger IBU shift by altering the amount of bittering hops rather than the boil length.. all of which leads me to suspect that the longer boil is mainly about driving more water off to create heavier body to the beer :hmm:

 

[Brewedout]

Well, it'll make the OG higher for a start with the extra boil evaporation losses...

Continuing to boil a more concentrated wort may also begin to give caramel flavours? (that's a guess!)

You will get a bigger IBU shift by altering the amount of bittering hops rather than the boil length.. all of which leads me to suspect that the longer boil is mainly about driving more water off to create heavier body to the beer :hmm:

I forgot to say thanks for the reply!