Beersmith Question

[SJW]

Why do the IBU's drop when the o/a boil time is reduced......EVEN THOUGH the boil time for the hops remains the same in the recipe? Try it , it's bizzar. Or is there less bitterness extraction with a shorter boil prior to the hops being added? I doubt :blink:

Steve

 

[Adamt]

Could if you first wort hop/mash hop I guess... I don't find any difference when i change my overall brew time in Beersmith.

Edit: I do get miniscule changes if "Set Boil Volume Based on Equipment" is activated... Shouldn't make any difference if the volume is the same at the end, the hop boil time is the same and evaporation rate is the same. The IBU changes are probably far less than the error tolerance in the calculations, let alone hop mass measurements so I wouldn't even bat an eyelid at this.

 

[bigfridge]

Why do the IBU's drop when the o/a boil time is reduced......EVEN THOUGH the boil time for the hops remains the same in the recipe? Try it , it's bizzar. Or is there less bitterness extraction with a shorter boil prior to the hops being added? I doubt :blink:

Steve

How much does it drop ?

Don't forget that the Gravity increases as you boil so this affects the efficiency of bitterness extraction.

Dave

 

[AndrewQLD]

Why do the IBU's drop when the o/a boil time is reduced......EVEN THOUGH the boil time for the hops remains the same in the recipe? Try it , it's bizzar. Or is there less bitterness extraction with a shorter boil prior to the hops being added? I doubt :blink:

Steve

Steve can you post the file of your recipe so we can load it into Beersmith and give you an answer, I can't be bothered inputing a recipe by hand but would like to help you out.

Cheers
Andrew

 

[SJW]

View attachment recipes1.bsmView attachment recipes.bsm

These are the 2 files and the only thing that has changed is the boil time, and notice that there is a small diff in the IBU. I know this is not enough to worry about but I dont understand why it would change at all. Maybe it has something to do with the different volumes of wort that the hops would be exposed to during the boil?

 

[KoNG]

weird, shows 30.8 IBU in both for me...

 

[SJW]

weird, shows 30.8 IBU in both for me...

With a boil time at 90min the IBU's are 30.6
With a boil time at 60min the IBU's are 29.9

But it would be a function of the pre boil volume I would say.

 

[KoNG]

of the two recipes you have posted there....
they came up on my BS as 120 minute boil and a 75 minute boil.
both at 30.8 IBU....

 

[warrenlw63]

Regardless I implore anybody to detect an 0.7th of an IBU difference. :blink:

Warren -

 

[Bobby]

would it be because of the variability of hop utilisation (bittering) depending on the gravity of the wort?
i.e I believe that a higher gravity wort will result in decreased hop utilisation.

 

[warrenlw63]

That's exactly it Bobby.

Warren -

 

[KoNG]

would it be because of the variability of hop utilisation (bittering) depending on the gravity of the wort?
i.e I believe that a higher gravity wort will result in decreased hop utilisation.

i was thinking the same Bobby, but that is the reverse of what SJW is experiencing.

he is saying that IBU's are dropping with 'less' boil time (which to me means you would have a lower gravity wort) so you would expect "increased" utilistaion.?

 

[SJW]

Its not really worth worrying about, just interesting!

 

[warrenlw63]

Not necessarily true... Wouldn't it mean that there's a larger post boil volume with the same amount of hops decreasing utilisation also ?? ie; same amount of hops going into a larger volume of liquid ?

Whip me if I'm wrong. :unsure:

Edit: Not decreased hop utilisation. Just theoretically less hops.

Warren -

 

[Bobby]

perhaps, but as the desired final gravity is the same in each case i would imagine that the volume and gravity of the 90 min wort after 30 minutes of boiling would be that same as the volume and gravity of the 60 min wort?

so perhaps not...
meh....it is what it is...much of a muchness

edit - if above is true my first guess would be wrong