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Home Brew Forums > Home Brewing Beer > Brew Science > Hop Extraction and Characterizing the Extracted Compounds
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Old 04-21-2009, 08:06 PM   #1
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Default Hop Extraction and Characterizing the Extracted Compounds

I am doing a special project in my organic chemistry class and am wondering if there is a fairly simple way to characterize the compounds I extract. I plan on boiling hop pellets in a ratio of 3g of hops in 25ml of ethanol for an hour, then cooling and filtering and drying under vacuum. I did the extraction at home using some gin I distilled down to somewhere near 80% ethanol and it definitely extracts the bittering compounds I just need a way to separate the acids from the essential oils and prove that they have been extracted. All of the papers I have found use high performance liquid chromatography or centrifugal partition chromatography neither of which I have access to. I do have access to NMR, mass spec, gas and column chromatography. Any help would be great, thanks

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Old 04-22-2009, 03:11 AM   #2
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This is supposed to be a mass-spectrograph and I believe the six sharp spikes are the bittering compounds. The article was rather vague.

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Old 04-22-2009, 04:19 AM   #3
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Using the logic of boil additions:
Short extractions will leave you with mostly flavor compounds, and long extractions will leave you with more of the bitter compounds.

I would also assume that the aroma compounds or more hydrophobic, and the bitter compounds more hydrophilic.

Putting these together, aromas should come out in a quick extraction with cold EtOH. After that boil the crap out of the hops in water. The volitile aromatics will vaporize, and you will be left with the bitters.

Another approach would be to destroy the aromatics through oxidation.

Also, be sure to choose different hops. Some are much higher on aromatics, while others are almost strictly bittering compounds.

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Old 04-22-2009, 07:29 AM   #4
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These might contain some useful information.

ADVANCES IN THE LIQUID-CHROMATOGRAPHY OF HOP BITTER COMPOUNDS
VERZELE M, STEENBEKE G, DEWAELE C, VERHAGEN LC, STRATING J
HRC-JOURNAL OF HIGH RESOLUTION CHROMATOGRAPHY

also

Hop (Humulus lupulus L.) proanthocyanidins characterized by mass spectrometry, acid catalysis, andgel permeation chromatography
Taylor AW, Barofsky E, Kennedy JA, Deinzer ML
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

Hope this helps.

~andrew

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Old 04-22-2009, 04:26 PM   #5
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NMR won't do you any good until you separate the compounds from one another. HPLC really is the way to go. I'm not sure the compounds are volatile enough to run through a GC without having to derivitize them first - which is probably why people use HPLC - saves a step.

You might be able to go old school and do this by thin layer chromatography. I bet there are some papers from the 70's or 80's that have a method. Hmmmm, that might be a way for the home hop grower to get an idea of the AA content of their hops.

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Old 04-23-2009, 01:16 AM   #6
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With some NMR skill, it should be easy to tell the components apart, but I don't know how much they'd pile up in a mixture. I'd just extract the hops with a non-polar solvent such as hexane, and run a liquid chromatography column on it. This should at least yield a crude separation.

The hydrogens on the carbon directly next to the carbonyl is where I'd look. I remember looking at some of the compounds in my NMR class. Are you looking at acids in raw hops, or the iso-alpha acids you get from boiling?

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Old 04-23-2009, 01:17 AM   #7
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Thanks for the responses. I forgot to mention I had access to solid and liquid IR too, not that it will really help without separating the compounds. Thanks for the articles I will have to check them out at school tomorrow all I can get right now is abstracts. When I was looking yesterday I couldn't seem to find any old school stuff, thin layer would be perfect though.

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Old 04-23-2009, 01:26 AM   #8
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Quote:
Originally Posted by CHansen6 View Post
With some NMR skill, it should be easy to tell the components apart, but I don't know how much they'd pile up in a mixture. I'd just extract the hops with a non-polar solvent such as hexane, and run a liquid chromatography column on it. This should at least yield a crude separation.

The hydrogens on the carbon directly next to the carbonyl is where I'd look. I remember looking at some of the compounds in my NMR class. Are you looking at acids in raw hops, or the iso-alpha acids you get from boiling?
Dont really have much NMR skill, just learning all that right now. I have been reading that you can get more out with a polar solvent which is why I am leaning towards ethanol. Not sure about the iso or raw, though after an hour boiling in ethanol, if that is how I end up extracting, then iso. Guess it really comes down to what I can find for papers on separation. My teacher wants something that has already been done, though I might be able to convince him to let me do a crude separation as you described
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Old 04-23-2009, 01:57 AM   #9
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Check the boiling temps of the things you want to separate you might be able to get away with a rotovap.

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Old 04-23-2009, 05:02 AM   #10
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Quote:
Originally Posted by Yeastie View Post
Check the boiling temps of the things you want to separate you might be able to get away with a rotovap.
The a acids are all very similar, really doubt that boiling points are very far off. Most of the molecule is the same just a different R group comming off the ring
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