Hops and IBU

[BrewHaus]

Thanks for all the help everyone with the partial query...I've now got one about bittering hops and IBU.

I know the amount of bitterness comes from OG, water level, hop alpha acid level and boil time but I'll a little confused about the times people are saying regarding hop boil time.

I've read in numerous places that it is recommended that people boil one ounce of hops for 60 and then add another ounce at 15 and 5 min.

BeerSmith's IBU calc goes right off the scale if this is input which would make a really bitter beer.

For example: 4 litres at a OG of 1050 (500gm LDM in 4 lt of water) with 25g Fuggles @15min and 25g Goldings UK @ 10 min gives 61.3 IBU

For 60 min for the Fuggles and still 10 for the Goldings I get 97.2 IBU!

To get a reasonable level, I need to use 15g for both with the same 15 + 10 min time and 1050 with 4 litres of water and I set get a 36.8 IBU which still is a reasonably bitter beer.

When your OG is higher you can boil more hops for the same time or just boil them longer...the query is how come many suggestions say 60 min of 25gm+ Fuggles strength hops with a 4 litre boil and 1050 OG when it would make an extraordinaryly bitter beer?

I'm a little confused now. Are my beersmith calc's way off?

[Kevnlis]

You are making a 4 litre batch?

Perhaps my sticky on partial boils can help?

http://homebrewandbeer.com/forum/viewto ... f=2&t=7834

[drsmurto]

4L boil but a full sized batch?

Beersmith can work all this out for you.

[BrewHaus]

Ok, I'm really confused now...

I'm trying kitchen partials where I use a couple of kilos of grain and then added LDME and/or extract/dex etc to make up the rest of the fermentables rather than using just a 1.7kilo tin of Coopers and a kilo of LDME.

I've read that when you try this method, it's simpler to bitter the brew by making up a 4l batch of 500gms LDM which comes in at 1050 OG which makes working out your IBUs easier.

The confusing thing is that if I plug the ratios into beersmith nothing seems right...

i.e.
if I use (see attached) 25 gm fuggles for 60 min and 25 gms of goldings at 1050 in a 4 litre boil I get 106.8 IBU
if I use (see attached) 25 gm fuggles for 60 min and 25 gms of goldings at 1050 in a 4 litre boil and a 21litre batch size I get 3 IBU

Even a 90 min boil using a 21 litre batch only gives me 3.2 IBU

Could someone help straighten me out here?

[Kevnlis]

My guess is that it is assuming you are boiling 4 litres worth of wort which contains enough sugars to make up 21 litres of 1.050 wort?

[Goofinder]

There's a way to make Beersmith work for you in this scenario... but I never figured it out.

Can you boil 7L? If you can, just put 1/3 the fermentables in the boil and the bitterness will end up the same as if you boiled the full 21L because you'll have the same boil gravity.

[drsmurto]

Hop utilisation seems to be much lower which i assume is due to the relative solubility of the alpha acids in wort. The larger the volume the more can dissolve but i suspect that i am over thinking the problem.

I agree that when you play with beersmith the IBU changes markedly between a 4L and an 8L boil.

Hmmmm. Seems i cant help out on this one. I think we should wait till TL sees this thread and gives his thoughts.

[pixelboy]

In Beersmith break your fermentables up so you can just mark what you are boiling..

For example I usually do
1kg LDME
1.5kg LME (Coopers Extract Can)
Hops

I boil 500gms of the LDME in 7L.

So I enter it into Beersmith as
1 x 500gms LDME
1 x 500gms LDME
1 x 1.5kg LME

Then on one of the LDME and the LME you tick "Add After Boil"

Then I set my boil volume to 7l! Hey Presto!

Edit: This is in the "Recipe" part of Beersmith.. not sure how to tweak the "Calculate Hop Bitterness" bit

[BrewHaus]

ok...I think I'm now understanding this...

I've plugged a 21 litre batch with a 4litre boil into the recipe section of Beersmith with .5kg of LDM (for a rough 1.046-1.050 OG), added 50gms of 4.5% fuggles for 60 min boil and then added 12.5gms of 5% goldings for 10 min for aroma (and a little bittering) just before the end of the boil. This comes out with 28.2 IBUs.

Is this right and will it bitter my 21litre brew correctly?

If so, this saves me heaps of stress and I can brew using my existing pots (which aren't quite big enough for whole brew batches - asking for an expensive huge pot from the other half is out of the quest at the moment) and have the right IBU at the end (or close enough anyway).

[Kevnlis]

Yes, that is the right way to do it.

[BrewHaus]

Fantastic...now I can progress onto some much improved partial grain beers which I bitter myself!

Thanks for everyone's help.

Cheers,
BrewHaus