IBU's For Coopers tins

[Chrisp]

Sorry people, I know it's on here, but I cant seem to find the IBU's for the Coopers kit cans. If someone could help i would really appreciate it.
Cheers Crisp

[gregb]

Try here.

Cheers,
Greg

[Chrisp]

Thanks for the link Greg. I am though a little confused. The tin IBU's on the Coopers site were in the hundreds, and yet reading through some of the other threads etc , the IBU's are between tthe low teens up to the mid twenties, and much higher again (into the 70's) for some beers.

[Bum]

Unfortunately Coopers (rather unhelpfully for some) give the IBU for the tin as is - before dilution. I'm sure you've tasted the goop from the tin? It is much more bitter than the finished beer, right? That's because the straight goop is 280IBU (or whatever number that particular tin happens to be).

I guess they express the IBU like that as they can't be certain what people are going to do with it (because more or less water will alter the final IBU). I wish they'd put a link to some formula or calculator where they show the IBU. Although they should be congratulated for how forthcoming they are with information in general - not all kit makers are so generous.

[fiat84]

Approximate calculation divide the posted kit ibu by 18.4 = real ibu
e.g. Coopers Mexican Cerveza kit ibu 270/18.4 = 14.67 real ibu

[Bum]

That calculation can only work at a set volume, surely? Sorry, too pissed to work it out myself right now.

[earle]

The formula is Coopers IBU / final volume x 1.25

The 1.25 takes into account the volume of the kit.

To build on fiat84's response assuming a 23L final volume:
Coopers Mexican 270IBU/23x1.25 = 14.67IBU

fiat is using a short cut formula which will work for 23L batches, use the above formula for other volumes.

Cheers

[Anna]

NOTE: The bitterness calculations below are based on a formula that was subsequently found to be incorrect. The correct calculations are substantially different and can be found on the second page of this thread - Oliver.

Hi guys - I calculated the IBUs of the Coopers kits in another thread. Here are my calcs:

Mexican Cerveza = 14.6
Australian Pale Ale = 18.5
Lager = 21.2
Canadian Blonde = 22.8
Draught = 22.8
Real Ale = 30.4
English Bitter = 32
Dark Ale = 32
Stout = 38.6

The calculation (thanks to Warra's link) was: Kit IBU / Final Volume x 1.25 (Kit IBUs are available on the Coopers website).

anna

[Bum]

Above method for calculating IBU for Coopers tins is incorrect. Formula given on Coopers webpage http://coopers.com.au/media/61084/brewing_faqs.pdf (scroll down to page 5) shows the IBU for a PA tin is just under 25. All the above figures will be out similarly.

The correct formula is: kit IBU*1.7/final volume

[Anna]

Well, I guess we should thank Bum for checking that formula! I just had a look at the Coopers' FAQs and apparently the amended calculation is prior to fermentation, whilst the calculation used by myself and others on this forum is after fermentation; therefore if you were keying the IBU of a kit into a software program you would have to use Coopers (and Bum's) formula.

This will also throw a spanner in the works of the BrewMate developer, who has just added Coopers kits to his list of fermentables, using the initial formula. Anna (Gotta go now and revise all my recipes in BrewMate!)

Hey Bum! Care to do the calcs again for all the kits and post for us?

[earle]

The quoted weight per volume dilution doesn't make sense when neither colour or bitterness units involve a weight. I understand they are referring of the weight of the extract but I am unsure of why they think that comes into it. I've been out of the science field for a while now. What do you reckon Doc?

[Bum]

The figure quoted on the webpage is per kilo of undiluted goop. That is why the weight comes into it. Diluting one kilo of goop will give a different IBU and colour than diluting 1.7kg to the same volume.

What I don't get is why Anna thinks fermentation has anything to do with it. Might change perceived bitterness but this has nothing to do with IBUs - does it? Very interested in a serious explanation.

[drsmurto]

The quoted weight per volume dilution doesn't make sense when neither colour or bitterness units involve a weight. I understand they are referring of the weight of the extract but I am unsure of why they think that comes into it. I've been out of the science field for a while now. What do you reckon Doc?

The IBU and EBC are given as per tin ie. per 1.7kg. Simply divided this by 23L assumes you are starting of with 1kg.

The use of weight rather than volume is a little confusing but since the extract is very concentrated using volume in this case would throw the calculations out of whack. Either that or you would need a few more numbers thrown in (namely density of the extract and the density of the final volume).

As for their comments about pre and post fermentation...... I don't understand enough about the volatility of iso-alpha acids. I would have assumed they were not scrubbed out during fermentation like the volatile aroma molecules. A drop of up to 30% is huge. I understand that over time in the bottle (or keg) the perceived bitterness decreases but i have never seen any research that shows the actual IBU decreases. I will do some digging into the literature.

EDIT - beaten to it by Bum.

[Anna]

Bum, I'm not pretending to know anything about fermentation - I'm just quoting off the Coopers' website, which I checked out after reading your post. viz:

"The figures we quote for colour and bitterness are specified for the product inside the can at the time
of packaging. Of course, the product is concentrated, hence the seemingly high figures. The figures
become more realistic once they are plugged into a formula for estimating the colour and bitterness of the reconstituted and fermented brew.
To calculate the bitterness of the brew: multiply the quoted product bitterness by the weight of the product
(1.7kg)* and divide by the total brew volume (normally 23 litres).
* We use the weight because our quoted colour/bitterness figures are based on a weight/volume dilution.
Product bitterness x 1.7 / Brew volume = Total bitterness before fermentation
As an example, if a brew is made with Mexican Cerveza up to a volume of 23 litres:
270 x 1.7 / 23 = 20 IBU (International Bitterness Units)
This figure represents the brew bitterness prior to fermentation. Generally, fermentation reduces colour
and bitterness by between 10 to 30%. So final bitterness of the fermented brew may be anything from 14 to 18 IBU.
Colour may be calculated in the same way. Ensure to add the colour contribution of all ingredients together.
Colour figures are quoted for liquid extract at the time of packaging as these products will darken with time.
The darkening process is accelerated by exposure to elevated temperature".

When I originially did the calcs, again I was just using a formula supplied by other members (odd that nobody questionned it at the time!). I only did the exercise to try to save others the legwork and am quite happy to have it corrected.

[drsmurto]

Anna - I would take the advice from Coopers with a grain of salt.

They are, after all, the same people who recommend fermenting your beer at 24+C.

Until i read some scientific argument as to why fermentation decreases the concentration of iso-alpha acids and a plausible mechanism for this reaction i am calling bullshit.

[Bum]

I can see you feel there is some vendetta here - I assure you that isn't the case. If my language seems curt I apologise.

I hope this doesn't aggravate the above issue but can you please quote the specific part of your post above that explains the pre/post fermentation bitterness difference thing? I don't see it myself.

You'll find there is a lot of information that has been posted and not brought into question in the past, Anna. Doesn't mean it is all correct. I happened to read an explanation of the calculation and saw the page linked on another board today and remembered this thread and hoped to help out future readers.

[Anna]

Here's the bit from the Coopers' quote I was referring to :

"Generally, fermentation reduces colour and bitterness by between 10 to 30%. So final bitterness of the fermented brew may be anything from 14 to 18 IBU."

I hope we can clarify this issue, because as you pointed out, it would affect the IBU of some recipes pretty drastically.

[Bum]

Man. I even read it twice looking for it! Thanks for the clarification, Anna. I guess I'll stay out of it until my jetlag subsides.

I can understand the colour changing dramatically (I'm sure we all notice this, no matter what method we use to make our wort) but I've gotta say 30% still seems a gigantic drop in bitterness.

[Anna]

Like the Doc says, we shouldn't take Coopers' word as gospel, so I guess we'll just have to wait for our resident scientists to have the final say.

It's all good!

[earle]

The IBU and EBC are given as per tin ie. per 1.7kg. Simply divided this by 23L assumes you are starting of with 1kg.

I agree. Thats why I usually do tin IBU/23x1.25. (Based on vol/vol dilution).

The use of weight rather than volume is a little confusing but since the extract is very concentrated using volume in this case would throw the calculations out of whack. Either that or you would need a few more numbers thrown in (namely density of the extract and the density of the final volume).

This is the bit that doesn't make sense to me. Given that IBU is basically bitterness units/volume, why would you not do a vol/vol diltion calc? Can you provide a bit more of an explanation, I need more convincing.