IBU's For Coopers tins

[drsmurto]

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.

Is 1.25 the volume of the tin?

[earle]

To tell the truth I don't think that I've ever measured it myself but yes 1.25L is supposed to be the volume of the tin. There have been threads on converting IBU of coopers tins before and kit IBU/final volume x 1.25 seems to have been the commonly accepted formula. I'm not saying that its correct because its commonly accepted, just as I'm not willing to accept the alternate version of the formula just because its on the cooper's website, but a vol/vol dilution makes a lot of sense.

[Bum]

Except that the IBU is given by weight not by volume.

[SuperBroo]

what are the tin dimensions ?
(I dont have one close by)

[earle]

Except that the IBU is given by weight not by volume.

I don't really accept that. The specified IBU is for a given amount of concentrate in a tin that they choose to market by weight. It could just as easily be marketed by volume. How they choose to market the tin should not determine the calculation.

One formula for IBU can be found here http://en.wikipedia.org/wiki/International_Bitterness_Units_scale

A formula craft brewers use to estimate IBU is:

IBU = (W x A x U)/(V x K)

, where
W refers to the weight of the hops used,
A refers to the alpha acid percentage, which is influenced by many factors, including cultivation method, species, and time of year — hops are often sold labeled with this percentage
U is the percentage of alpha acid that is actually used during the boiling process
V means the volume of the wort,
K is a constant factor that adjusts the measurement to account for the units used.
For grams and litres K = 10.0.
For avoirdupois ounces and imperial gallons K = 1.61.
For avoirdupois ounces and US gallons K = 1.34.

Which basically means that IBU is bittterness units per volume of wort. Thats why I don't understand why weight should come into it.

[drsmurto]

Coopers use 1.7kg in the calculation which means that all the tins contain 1.7kg of extract.

By assuming that all the tins contain 1.25L you are making the assumption they have the identical specific gravity (density).

Since that is never stated on the tin (or the website) how can you make that assumption?

Sorry for being pedantic, it's highly likely all the tins contain a similar specific gravity (in which case its a moot point) as this would make production simpler but until Coopers clarify this its only an assumption.

[Bum]

Except that the IBU is given by weight not by volume.

I don't really accept that. The specified IBU is for a given amount of concentrate in a tin that they choose to market by weight. It could just as easily be marketed by volume. How they choose to market the tin should not determine the calculation.

One formula for IBU can be found here http://en.wikipedia.org/wiki/International_Bitterness_Units_scale

A formula craft brewers use to estimate IBU is:

IBU = (W x A x U)/(V x K)

, where
W refers to the weight of the hops used,
A refers to the alpha acid percentage, which is influenced by many factors, including cultivation method, species, and time of year — hops are often sold labeled with this percentage
U is the percentage of alpha acid that is actually used during the boiling process
V means the volume of the wort,
K is a constant factor that adjusts the measurement to account for the units used.
For grams and litres K = 10.0.
For avoirdupois ounces and imperial gallons K = 1.61.
For avoirdupois ounces and US gallons K = 1.34.

Which basically means that IBU is bittterness units per volume of wort. Thats why I don't understand why weight should come into it.

IBU is a representation of iso-alpha acids (measured in weight) per volume of beer. Weight is fundamental to IBU calculations. Regardless, Coopers give the IBU for a kilo of their goop. Why? Dunno (perhaps it simplifies the calculations for any of us dumb bastards who might want to build one of their beers) but they do and so we must allow for the amount of the goop used which requires us to multiply by weight used.

[earle]

Thats a very fair point Doc. However the tins are all the same size so as you say it could be a moot point. (I'm not assuming they are all filled the same amount though).

That aside, am I wrong to think about IBU in the same way as molarity?

[earle]

Regardless, Coopers give the IBU for a kilo of their goop.

Thanks Bum. You've just answered the question for me. I was working on the basis that the quoted IBU was for a whole tin. If it's per kilo then the x1.7 makes perfect sense.

Cheers

[Anna]

So, if that's settled, who's gonna do the new calcs? They are very handy to have on the forum as a sticky.

Anna

[drsmurto]

So, if that's settled, who's gonna do the new calcs? They are very handy to have on the forum as a sticky.

Anna

The calculations work fine using the formula - Final IBU = IBU of tin * 1.7 / volume of batch. I'd stick with that.

[Anna]

Ok then - here we go! (However, I'm still puzzled by Coopers' claim that IBU drops 10-30% during fermentation. Some of the software around will need revising if that is not the case. )

Using the formula: IBU of tin*1.7/23

Beer = IBU on can = IBU (based on 23L)
Lager = 390 = 28.8
Draught = 420 = 31.0
Dark Ale = 590 = 43.6
Real Ale = 560 = 41.4
Stout = 710 = 52.5
Pale Ale = 340 = 25.1
Mex Cerveza = 270 = 20.0
Can Blonde = 420 = 31.0
English Bitter = 590 = 43.6
Euro Lager = 340 = 25.1
Heritage Lager = 390 = 28.8
IPA = 710 = 52.5
Irish Stout = 560 = 41.4
Aust Bitter = 495 = 36.6
Pilsner = 420 = 31.0
Sparkling Ale = 490 = 36.2
Trad Draught = 420 = 31.0
Wheat Beer = 300 = 22.2

Yes, I'm bored at work again!

Anna (Sorry, can't get the table to tabulate properly - it looks OK when I type it! )

[drsmurto]

I'd ignore the apparent drop in IBU during fermentation Anna that Coopers report.

This is the first time i have heard of it on any brewing forum and its not in any of the brewing text books I've read.

I'll dig out my copies of 'Principle of Brewing Science' by Dr George Fix and 'Tap into the Art and Science of Brewing' by Prof Charles Bamforth and see if there is anything in there about it.

[gregb]

Useful info here, I've made it a sticky.

[Chrisp]

good work guys. thanks for the calculations anna. Makes a big differance to batch IBU though
re-calculated most recent brews tonight, eg Irish red i thought was 26 IBU is acctually 35.7 IBU .

[Bum]

Still tastes the same, but.

[Anna]

good work guys. thanks for the calculations anna. Makes a big differance to batch IBU though
re-calculated most recent brews tonight, eg Irish red i thought was 26 IBU is acctually 35.7 IBU .

Yeah, I did all mine again too - explains a lot!

[Finnagann]

I'd ignore the apparent drop in IBU during fermentation Anna that Coopers report.

This is the first time i have heard of it on any brewing forum and its not in any of the brewing text books I've read.

I'll dig out my copies of 'Principle of Brewing Science' by Dr George Fix and 'Tap into the Art and Science of Brewing' by Prof Charles Bamforth and see if there is anything in there about it.

Any luck here Doc? Are Anna's numbers pretty close do you think?

[earle]

Perhaps they are referring to the difference between actual IBU and perceived IBU caused by the hops/malt balance in beers???

[drsmurto]

Haven't got around to reading the texts but have been reading How to Brew as well as studying for the BJCP exam which includes a section on fermentation and i still haven't seen this mentioned.

I'll ask a few people i know are doing uni studies in brewing and see what they can come up with.

The fact it has never come up on any forum seems strange. The AHB membership contains several professional brewers (both megaswill and craft) and this point has never been raised.

The only thing i can think of is the calculated vs actual IBU debate.....

And the only way to test IBU in a beer is via expensive chromatographic techniques which can be quite expensive.

I'll set a reminder for myself to have a look in the texts this week some time.