Kit IBUs combined with added hops

[Pale_Ale]

Hi all,

I am trying to find an effective way of calculating IBUs of a brew that uses a kit. The link below shows the IBUs for each Coopers kit.

http://www.bobbrews.com/cooperskits.html

Few questions:

1) Are the IBUs in a kit based on i) no added malt and ii) 23 litres of water

2) Does anyone have a list of commercial beers and their IBUs? This would be handy for using a commercial beer to compare.

3) How does everyone else go about this (for kits)?

Currently I use an IBU calculator to figure out IBUs of added hops, I assume you can just add the IBUs of the kit with the IBUs of your added hops.

Cheers all

[Ahutchy]

Hi Pale Ale,

My thoughts are that its for 23l and malt additions will make no difference to the actual number as it applies to any given recipe.

Thats what I do anyway.

Commercial beers often have the details on the breweries website.

example - http://www.sierranevada.com/beers/paleale.html

Have fun, Andrew.

[Pale_Ale]

But aren't the IBUs affected by gravity which would be affected by the addition (or not) of malt?

[Ash]

That's what I thought Pale_Ale, you do balance hops & malt after all so there must be a relationship - unless there is an unknown to me measure of maltyness that goes up in a ratio to IBUs?

[111222333]

I'm pretty sure that the only time that is a factor is when you are doing your own boil. I may be wrong on that though.

[Ahutchy]

Yeah but...

Oh buggered if I know, now I'm confused.

Gravity of the boil decides hopping efficiency.

This I presumed Coopers had taken into account.

They have calculated their IBU as per any AG brewer would.

If you boil the kit it is going to change, downwards one presumes.

I dont boil kits, no point.

If you are going to boil the kit you shoulf have just bought un-malted extract and hopped as per your own wish during a preferably full volume 60 min boil.

If you do a high gravity boil hop efficiency falls dramatically. Something along the lines of 30 - 50% more hops would be required for a 7-8 litre boil versus 23l but don't quote me as I have forgoten most of what I ever knew through (presumably) alcoholic brain cell destruction.

Andrew.

[Pale_Ale]

Sorry, I think I've confused things by not being clear.

What I'm trying to work out is whether a certain recipe will be too bitter, based on the IBUs of the kit and the IBUs of the extra hops I add.

So my question regarding whether the IBU of the kit applied to 23L was based on this assumption: If you use 18L (not boil volume, total volume) with the kit, you will get a heavier bodied beer with more malt and more bitterness. This is because you are distributing the same matliness and bitterness throughout less volume of liquid. So my question is whether the IBUs are based on a 23 litre volume, because surely the IBU of the beer would go up with less volume and down with more volume of water in the primary fermentation.

The recipe I am doing is Thomas Coopers Sparkling Ale. What I'm trying to work out is whether it will be too bitter or too malty if I add the kit, 1.5kg of liquid malt, then 15g of Amarillo at 30, 15, and 0 minutes each.

In this case, what would be the best way of working out whether this will achieve a good balance for the style (Short of brewing it up!)

I figured I would need to combine the IBUs of each of my hop additions + the kit IBUs. I am even confusing myself now.

[Ahutchy]

Hi again,

Those doses of Amarillo probably won't add much bitterness anyway, assuming less than a full volume boil. Should add some nice hop notes though.

In regard to the smaller brew volume, I would think that would up the IBU as I am fairly sure it would be calculated at 23l.

Maybe some software like http://www.beersmith.com/ might help.

It will certainly allow you to understand what IBU is achieved for a given hopping amount versus boil time and boil volume.

I have found Beersmith pretty good and worth buying.

Your closing remark makes sense to me.

My kit brews at the moment involve combining two kits with appropriate IBU's to add up to the bitterness level I need for a particular brew and then add xtal extra aroma hops etc.

Seems to work pretty well. Haven't got any finalised recipes just yet though.

A lager thats just finishing at the moment seems particularly well balanced though. Perhaps just a bit of dry hopping in secondry??!!

Andrew.

[Pale_Ale]

Hi Andrew,

Thanks for advice. Has cleared a few things up.

According to IBU calc it would add about 23 IBU. I have 9.5% AA.

Beersmith suggestion is a good one, I probably should get it.

Adding 2 kits together is probably a much simpler way of achieving what I'm after.

With your lager, I guess any good kit will have the right malt/hops balance so maybe I'll give that a go too.

Be interested to read your finalised recipes.

[Ahutchy]

Hi again PA,

I ran the numbers thru BS and came up with the following BS!!

Your hop schedule in a full boil is worth 18.5 IBU.

Same again with boil vol reduced to 6l gets only 7.6IBU.

Bigger diff than I remember.

Recipe coming soon for the lager I have almost ready for CCing once I have established that its worth talking about.

Andrew.

[Pale_Ale]

Ok, I am learning here. Does boil volume affect hop efficiency? If so, why? I thought gravity affected hop efficiency.

I am using the rooftop IBU calc and enter the batch volume in as 6 Gallons (22.7L) which is my total 'batch' size. Maybe I am presuming they mean total batch and not boil volume.

I get 23.1 IBUs on the above basis.

Reducing the volume increases the IBU.

Cheers
Pale

PS Want to do a lager soon so would be interested in results

[Oliver]

Ok, I am learning here. Does boil volume affect hop efficiency? If so, why? I thought gravity affected hop efficiency.

Ah, yes, but the two are tied. A boil of a larger volume will have a lower gravity than the same ingredients in a smaller volume.

For instance, if your boil volume was doubled, your gravity would be halved.

Oliver

[BierMeister]

I don't use an online calculator as I believe that it's just as good if not better to do it with the good old pencil. I find it helps to see how all the different ingredients effect the outcome.

IBU=weight of hops x alpha acid x utilisation
>>>>>>>>>>>volume brewed x 10

weight of hops in grams
volume in litres
AA is in percent
hop utilisation is in percent and usually between 20% and 35%

Given the different methods etc... if you use 20% then you will get about as good a calculation as you need.

It's in the utilisation that you get the most variation and its due to the differences in gravity, boil times, hop freshness, vigour of the boil etc...

ie IBU=50gms hops x 6%AA x 20%
>>>>>>>>>>>23L x 10

IBU=26

or IBU=50gms hops x 6%AA x 35%
>>>>>>>>>>>23L x 10

IBU=45

note the difference when compared to just changing the volume.

IBU=50gms hops x 6%AA x 20%
>>>>>>>>>>>18L x 10

IBU=33

It has been recommended and I find it the most realistic to use 20% utilisation. Don't forget that the volume is the boil volume not the volume you end up with in the fermentor.