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Home Brew Forums > Home Brewing Beer > Brew Science > Testing for Actual IBU's
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Old 07-17-2012, 11:49 PM   #11
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Minute is indeed kind of iffy. For the pipeting of the beer the purpose is to prevent the beer from foaming in the pipet so the volume can be read accurately. It takes very very little. As I noted in an earlier post dipping the pipet tip in octanol, letting it drain and then whipping the pipet through a circular ark will throw most off. The MOA wants even this miniscule amount accounted for in the blank. I moisten the replaceable tip of a micropipetter with octanol and then just touch it to the side of the reference cuvet.

No - you do not decarbonate the beer. The MOA calls for withdrawing a 20 mL sample from cold, carbonated beer. The octanol takes care of the potential foam.

I would guess that the place where variation is greatest is in the extraction. See if you can find a used Burell Wrist Action shaker. Once you see one of these you will be convinced that this is what the people who wrote the MOA had in mind.

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Old 07-18-2012, 12:49 AM   #12
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Thanks! If you want to test wort though, pre pitch, is it sitll the same protocol? I would like to be able to update them on their utilization from a single 20-30 minute addition....I'm hoping it's still under 100% and I can extrapolate backwards where the true bittering addition would be.

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Old 07-18-2012, 01:20 AM   #13
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Yes, I would think so. Don't believe there is an MOA for wort though. Obviously you wouldn't need the octanol as there is no foam to deal with in the case of wort but it would probably be a good idea to use it anyway just to make sure everything is apples to apples.

I question the value of doing this to wort. I guess you could see how much additional boiling time increases the apparent IBU (remember this is a measure that 'adequately describes beer bitterness' not some absolute measure of mg/L isohumulone though it is apparently well correlated with that. Because of this fact and that utilization includes things that happen in the fermenter (i.e. the yeast strip a lot of bitter - ever wonder why Vegemite/Marmite taste the way they do?) I'm not sure that anything other than a relative interpretation is valid. Guess you could compare a just pre-pitch wort sample to a finished beer sample and scale all wort measurements back by the IBU ratio so determined.

Also keep in mind that a sample run is a fair amount of work (especially if you are shaking by hand). It takes about 20 minutes to do a test - longer if the dreaded 'slush' forms during extraction. This then has to be centrifuged, broken up and centrifuged again. Add another 5 minutes or so for that.

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Old 07-18-2012, 01:48 AM   #14
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Quote:
Originally Posted by ajdelange View Post
No - you do not decarbonate the beer. The MOA calls for withdrawing a 20 mL sample from cold, carbonated beer. The octanol takes care of the potential foam.
I have had good and repeatable results using de-gassed beer and you do not need to mess with the octanol at all.
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Old 07-18-2012, 03:24 AM   #15
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Originally Posted by enricocoron View Post
White labs has IBU testing advertised at $48 on their website, not a bad price.
Hopunion will do it for $20 now.

$40 for IBU, ABV, Color, pH and a couple other tests.
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Old 07-18-2012, 01:05 PM   #16
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From Beer - 23A "Transfer 10.0 mL chilled carbonated beer (50°F) to a
50-mL centrifuge tube using a volumetric pipet that has
had a minute amount of octyl alcohol (reagent c) introduced
into the tip."

There is a reason for having standards: standardization. If you measure bitterness using the MOA and I measure bitterness using the MOA then people are comfortable with the notion that your measurements and mine are comparable. That's because in the process of developing the MOA several iterations of refinement and collaborative testing were carried out with the goal of getting the inter-laboratory (and, of course, intra laboratory) CV (coefficient of variation - the standard deviation divided by the mean) down. If an investigator can demonstrate that using warm degassed beer does not increase (or better still, decreases) the inter laboratory CV then he should write to the Standards Committee reporting his findings and proposing that the MOA be modified. This would (or could) result in another round of collaborative tests which, if they demonstrated that the CV was indeed not impaired or improved, would result in a modification to the published MOA. In other words, there is a reason that paragraph is in the MOA. If you are modifying the MOA for your own internal purposes then you can do as you wish but if you are charging people for analysis then it is incumbent upon you to follow the standard as closely as you can or at least inform your customers that you are not.

Beyond that using a little octanol is, IMO, a lot less trouble than degassing and find it interesting that foam always collapses too quickly in the glass and takes much to long to collapse in the lab.

Note: In looking back I see that I numbered the MOA incorrectly in a previous post. It is Beer-23. Also I indicated that N HCl is used. It is actually 3 N. The previous posts have been corrected.

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Old 04-03-2013, 05:06 AM   #17
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Quote:
Originally Posted by enricocoron View Post
Thanks! If you want to test wort though, pre pitch, is it sitll the same protocol? I would like to be able to update them on their utilization from a single 20-30 minute addition....I'm hoping it's still under 100% and I can extrapolate backwards where the true bittering addition would be.
Beer-23 covers both wort and beer.
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Old 04-05-2013, 12:22 AM   #18
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Hopunion will do it for $20 now.

$40 for IBU, ABV, Color, pH and a couple other tests.
I know this post is several months old but I just contacted them (Alpha Analytics) and the pricing has gone up to $30 for the IBU testing. He said pricing has gone up for a number of tests but did not go into any detail
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Old 04-05-2013, 06:11 PM   #19
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I haven't actually tried it yet despite having the reagents....White labs is down the street and after two results I have a fairly accurate constant I use along with Tinseth formula for my system. That is cheaper than WL though....

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