Is there a Hop Alpha Acid Test Kit?

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Is there a Hop Alpha Acid Test Kit?

Postby BrewBird » Mon Mar 19, 2007 9:58 am

So I'm growing my own hop plants and want to test the alpha acids without actually sending them in for testing.

I work in a lab but don't know the AA chart or the procedure for doing this.
Thanks,
BB
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Postby Triple Freak » Mon Mar 19, 2007 11:32 am

If you want to know the AA, you'll have to send them to a lab. There are no test kits out there.
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Postby Stevo » Mon Mar 19, 2007 12:04 pm

Just go by the average AA for the type of hops. Unless you like throwing money away, that is.
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Postby josephus » Mon Mar 19, 2007 12:50 pm

I know this looks long but if you work in a lab chances are you have access to a UV-Vis spectrophotometer, a benchtop centrifuge, and some common solvents. I've used this method and got very repeatable results that matched the reported value on the purchased hops. Be really carefull about exposing the extracted hops oils to light. You may also want to increase decrease the amount of dilution in each step since your hops may not be as high in acid as ones grown commercially.

Alpha and Beta Acids in Hops
(reference: ASBC MoA. 8th edition, 1992)
Method
1. Place 5.000 +/- .001 gr pulverized hops in an extraction bottle and add 100 mL toluene.
2. Shake for 30 min with vigorous agitation.
3. Let stand until clear or centrifuge (preferred).
4. Dilution A: Dilute 5.0 ml of this extract to 100 mL with methanol.
5. Dilution B: Dilute an aliquot of the dilution A with alkaline methanol (0.2 mL 6M NaOH per 100 mL MeOH) so that the Abs at 325 and 355 falls within the most accurate range of the instrument.
6. Immediately read dilution B (1 cm) at 275, 325 and 355 vs a toluene blank that was prepared and diluted in EXACTLY the same manner.
Notes:
? Hexane may be substituted for toluene
Calculations:
Dilution factor, d= (volume dil A x volume dil B)/ (500 x aliq extract A x aliq dil A)
% alpha acids= d x (-51.56 A355+ 73.79 A325-19.07 A275)
% beta acids= d x (55.57 A355-47.59 A325 + 5.10 A275)
Example:
1. 5 gr hops extracted with 10 mL toluene
2. 5 mL clear extract diluted to 100 mL with methanol=Dilution A
3. 3 mL Dilution A diluted to 50 mL with alkaline methanol
4. Absorbances
o A355=0.615
o A325= 0.596
o A275=0.132
d = (100 x 50) / (500 x 5 x 3) = 0.667
alpha = 0.667 x [ -(51.56 x 0.615) + (73.79 x 0.596) - (19.07 x 0.132) = 6.5
beta = 0.667 x [ (55.57 x 0.615) - (47.59 x 0.596) + (5.10 x 0.132) = 4.3
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Postby Saco_De_Toro » Mon Mar 19, 2007 12:54 pm

If you plan on growing your own hops, do a fresh hop beer. That's the biggest advantage homebrewers may have over micros and certainly macros. Like BrewBird said, just go by the average AA for the particular hop. Plan on making an American IPA or similar. It'd be almost impossible to overhop with fresh green hops. At least that's what Vinnie Cilurzo says. I've yet to get any bad advice from him.

As a note, I believe Sierra Nevada has an advanced gas chromatograph that's capable of doing very complex and accurate chemical analysis of beer. I think that's where Pizza Port and Russian River sent a few of their beers for determinate analysis. It turns out that the actual IBUs were very different from what Pro/Mash was calculating. I think Pliny the Elder was actually somewhere around 66 IBUs.
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"Beer - It's What's For Dinner"
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Postby BrewBird » Mon Mar 19, 2007 1:48 pm

THANKS Josephus!!
This works out very well.
BB


josephus wrote:I know this looks long but if you work in a lab chances are you have access to a UV-Vis spectrophotometer, a benchtop centrifuge, and some common solvents. I've used this method and got very repeatable results that matched the reported value on the purchased hops. Be really carefull about exposing the extracted hops oils to light. You may also want to increase decrease the amount of dilution in each step since your hops may not be as high in acid as ones grown commercially.

Alpha and Beta Acids in Hops
(reference: ASBC MoA. 8th edition, 1992)
Method
1. Place 5.000 +/- .001 gr pulverized hops in an extraction bottle and add 100 mL toluene.
2. Shake for 30 min with vigorous agitation.
3. Let stand until clear or centrifuge (preferred).
4. Dilution A: Dilute 5.0 ml of this extract to 100 mL with methanol.
5. Dilution B: Dilute an aliquot of the dilution A with alkaline methanol (0.2 mL 6M NaOH per 100 mL MeOH) so that the Abs at 325 and 355 falls within the most accurate range of the instrument.
6. Immediately read dilution B (1 cm) at 275, 325 and 355 vs a toluene blank that was prepared and diluted in EXACTLY the same manner.
Notes:
? Hexane may be substituted for toluene
Calculations:
Dilution factor, d= (volume dil A x volume dil B)/ (500 x aliq extract A x aliq dil A)
% alpha acids= d x (-51.56 A355+ 73.79 A325-19.07 A275)
% beta acids= d x (55.57 A355-47.59 A325 + 5.10 A275)
Example:
1. 5 gr hops extracted with 10 mL toluene
2. 5 mL clear extract diluted to 100 mL with methanol=Dilution A
3. 3 mL Dilution A diluted to 50 mL with alkaline methanol
4. Absorbances
o A355=0.615
o A325= 0.596
o A275=0.132
d = (100 x 50) / (500 x 5 x 3) = 0.667
alpha = 0.667 x [ -(51.56 x 0.615) + (73.79 x 0.596) - (19.07 x 0.132) = 6.5
beta = 0.667 x [ (55.57 x 0.615) - (47.59 x 0.596) + (5.10 x 0.132) = 4.3
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Postby Stevo » Mon Mar 19, 2007 6:52 pm

Wow, I never thought it would be that easy to test the AA%. I think I might do that on last years hop crop.

I don't have any reagent grade methanol or toluene, but I might just try hardware store stuff, since it doesn't have to be too sensitive anyway.....
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Postby josephus » Tue Mar 20, 2007 5:37 am

Stevo wrote:Wow, I never thought it would be that easy to test the AA%. I think I might do that on last years hop crop.

I don't have any reagent grade methanol or toluene, but I might just try hardware store stuff, since it doesn't have to be too sensitive anyway.....


Well the procedure is easy but it does take about an hour or so and you do need volumetric glassware which can be expensive. On the other hand if you have the stuff its worth an hour once a year to get some more info.
Non-reagent grade toluene should be fine since its for the extraction and the methanol should be at least 190 proof.
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Postby Stevo » Tue Mar 20, 2007 6:17 am

Scott,

You can buy Toluene at the hardware store, and Methanol at the auto parts store.

If you have access to the equipment it's an interesting, and yes simple, thing to do. If you can count, you can measure volumes in glassware! :wink:
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Postby josephus » Tue Mar 20, 2007 6:22 am

fossilsrocks wrote:Well, that all seems simple enough :roll: :lol:

Sorry, but that all seems a tad difficult for the average home brewer. Plus, are those chemicals readily available to individuals? Many chemicals are regulated (Or at least monitored) to keep meth labs from popping up everywhere.

Scott

I agree and I never said it was for the average anyone. You could order these chemicals from any chemical supplier. You can't make meth with wood alcohol and paint thinner but you could go blind if you drink them. I posted this because I thought it could help brewbird or anyone else who works in or has access to a lab and has basic knowledge of chemistry not because I thought every home hop grower should run out and buy all this stuff and play chemist :)
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Postby Stevo » Tue Mar 20, 2007 7:08 am

Sodium Hydroxide can be purchased at the hardware store as Red Devil Lye, missed that one.

Your point is well taken Scot, but none said Joe Schmoe should go do this, you need a spectrophotometer anyways, so that eliminates 99% of us.

fossilsrock wrote:The general public has enough trouble handling basic solvents & gasoline!


The general public can't even be trusted to buy food high in saturated fat, let alone gasoline!!!!!!! :shock:
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Postby BrewBird » Wed Mar 21, 2007 4:34 pm

BrewBird wrote:4. Absorbances
o A355=0.615
o A325= 0.596
o A275=0.132
d = (100 x 50) / (500 x 5 x 3) = 0.667
alpha = 0.667 x [ -(51.56 x 0.615) + (73.79 x 0.596) - (19.07 x 0.132) = 6.5
beta = 0.667 x [ (55.57 x 0.615) - (47.59 x 0.596) + (5.10 x 0.132) = 4.3
[/quote]

CRAP! I don't have A325 or A275 filter for my spectrophometer

What I can do is use already tested hops I get from B3 or freshops and make my own standard curve using A355 and A405
What do you think Josesfus?
I wonder if the curve is linear??
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Postby abike2many » Wed Mar 21, 2007 5:18 pm

fossilsrocks wrote: The general public has enough trouble handling basic solvents & gasoline! That's all I was saying.


Hey man, go easy there. I don't have a problem handling gasoline, I have a problem with matches!

Thanks for the procedure josephus.
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