Home Brew Forums

Home Brew Forums (http://www.homebrewtalk.com/forum.php)
-   Hops Growing (http://www.homebrewtalk.com/f92/)
-   -   How do you determine the AA%? (http://www.homebrewtalk.com/f92/how-do-you-determine-aa-55704/)

mongrell 02-19-2008 10:25 PM

How do you determine the AA%?
 
A friend of mine has natural hops growing in his back yard. How can you determine the AA% in them and should I dry them out or use them wet freshly picked.

Donasay 02-19-2008 10:29 PM

You send them to the lab to figure out the AA%. The problem with growing fresh hops is you don't know the AAU's so you could be making a beer with 4% or at 14%. The only way is to either experiment with the hops or to use hops you know the AAU on for bittering and the home grown hops for flavor and aroma.

Some people say the best thing to do is buy a food dehydrator and dry them out in there. My friend who grows them puts them in the oven for a while to dry them out, but that supposedly converts some of the alpha acids and ruins the bittering potential, but again we mainly use them for flavor and aroma not bittering.

Brewsmith 02-19-2008 10:32 PM

Don't dry them, just use them wet. You will need 5 or 6 times the amount of hops than the normal dried ones in a recipe since most of the weight of wet hops is water.

david_42 02-19-2008 11:16 PM

If you can identify the type, you'll be able to get some idea of the AA, but it takes serious lab equipment to quantify it.

Wet/fresh hops ales are really great! This year the Fresh Hop Fest did a tour of four cities in Oregon, it has become so popular. Two years ago, I did a Whole Harvest ale. Had five bines in their first year, so I just had enough for one batch.

jdoiv 02-19-2008 11:56 PM

One of the guys in my club found this. You may need access to a nice lab to do it though.


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

wildwest450 02-20-2008 12:02 AM

Quote:

Originally Posted by jdoiv
One of the guys in my club found this. You may need access to a nice lab to do it though.


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


I wanted to poke out my eye's with a stick after reading that.:confused:

HairyDogBrewing 02-20-2008 02:14 AM

Quote:

Originally Posted by jdoiv
One of the guys in my club found this. You may need access to a nice lab to do it though.
...
o A355=0.615
o A325= 0.596
o A275=0.132

For the non-scientists, oA355 etc are specific wavelengths (colors) of light absorbed by the sample.
You'd need a gas chromatograph ($$$$) to perform this procedure.
Definitely not DIY.

Parker36 02-20-2008 02:22 AM

Quote:

Originally Posted by egolla
You'd need a gas chromatograph ($$$$) to perform this procedure.
Definitely not DIY.

Or access to any half decent chem lab. Maybe its time for the homegrowers to take up a fall semester general chem lab at the local university. Its really not that hard of a process, the math just makes it look crazier than it acutally is.

Cookiebaggs 02-20-2008 02:27 AM

The guy I know who grows hops got a spec sheet from the supplier where he bought the rhizomes. They gave an AA range for that particular cultivar.

I just used the number in the middle of the range as a base and winged it in my first few batches. :)

I'm a hophead so if it was a little strong, I didn't care.

mrkristofo 02-20-2008 03:57 AM

Quote:

Originally Posted by jdoiv
One of the guys in my club found this. You may need access to a nice lab to do it though.


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

Um yeah....easy peasy. I can do that for anyone that's interested. Deal is I keep the extra hops, and I do it when it fits with my schedule. Let me clear it with the PI first, but it shouldn't be a problem at all so long as it's small-scale and kept quiet.


All times are GMT. The time now is 08:38 AM.

Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.