I've been given some hops but I don't know their AA. How can I test? Is it really this difficult? :hmm:
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) = 4.3josephus
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) = 4.3josephus
