Alpha Acid Chemical Makeup
- Thread starter Parker36
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mrkristofo
Well-Known Member
Yeah, actually, I put it in the wiki.
https://www.homebrewtalk.com/wiki/index.php/Alpha_acid#Alpha_acids
Working on R-groups for all the alpha acids, but no time.
https://www.homebrewtalk.com/wiki/index.php/Alpha_acid#Alpha_acids
Working on R-groups for all the alpha acids, but no time.
mrkristofo
Well-Known Member
Parker36 said:
You're a geek.
Fortunately, so am I. If you want to really read the fundamentals of brewing chemistry and microbiology, I suggest looking at the CRC Guide to Brewing Science and Practice. CU Boulder probably has a copy in the library.
Give me a few minutes in ChemDraw and I'll have your answers...
EDIT: There's 51 pages on the chemistry of hop constituents alone...
mrkristofo
Well-Known Member
There's 6 identified R-groups, (note that I modified the R in the picture such that the ketone is now part of "R").
R, alpha-acid
isovaleryl, Humulone
isobutyryl, Cohumulone
2-methylbutyryl, Adhumulone
propionyl, Posthumulone
4-methylpentanoyl, Prehumulone
hexanoyl, Adprehumulone
4-methylhexanoyl, unnamed
The following papers are probably of interest to you:
MOIR, M. (2000) J. Amer. Soc. Brew. Chem., 58, 131. (of particular interest)
STEVENS, R. (1967) Chem. Rev., 67, 19.
WINDISCH, W., KOLBACH, P. and SCHLEICHER R. (1927) Wochschr. Brau., 44, 453.
The Moir paper in the JASBC is a very good one, as it provides a millenium-review of what we know of hop chemistry. It was quite a good read, in fact. In it, it references the following paper which proposed the specific mechanisms of the isomerization:
De Keukeleire, D., and Verzele, M. The absolute configuration of
the isohumulones and the humulinic acids. Tetrahedron 27:4939-
4945, 1971.
Unfortuanately, I don't have access to Tetrahedron like I do the JASBC, but I'll let you know what I find when the article comes in.
So, the mechanism I am unsure of, but it doesn't occur on a stereo center of the R-group:
https://www.homebrewtalk.com/wiki/images/8/84/Iso-alpha-acids.png
Wish I had more to say about it, but between not having the paper handy and risking copyright infringement of what I've got, this is what I can tell you.
Remember, it's all just chemistry.
EDIT: Wow that image it huge...
R, alpha-acid
isovaleryl, Humulone
isobutyryl, Cohumulone
2-methylbutyryl, Adhumulone
propionyl, Posthumulone
4-methylpentanoyl, Prehumulone
hexanoyl, Adprehumulone
4-methylhexanoyl, unnamed
The following papers are probably of interest to you:
MOIR, M. (2000) J. Amer. Soc. Brew. Chem., 58, 131. (of particular interest)
STEVENS, R. (1967) Chem. Rev., 67, 19.
WINDISCH, W., KOLBACH, P. and SCHLEICHER R. (1927) Wochschr. Brau., 44, 453.
The Moir paper in the JASBC is a very good one, as it provides a millenium-review of what we know of hop chemistry. It was quite a good read, in fact. In it, it references the following paper which proposed the specific mechanisms of the isomerization:
De Keukeleire, D., and Verzele, M. The absolute configuration of
the isohumulones and the humulinic acids. Tetrahedron 27:4939-
4945, 1971.
Unfortuanately, I don't have access to Tetrahedron like I do the JASBC, but I'll let you know what I find when the article comes in.
So, the mechanism I am unsure of, but it doesn't occur on a stereo center of the R-group:
https://www.homebrewtalk.com/wiki/images/8/84/Iso-alpha-acids.png
Wish I had more to say about it, but between not having the paper handy and risking copyright infringement of what I've got, this is what I can tell you.
Remember, it's all just chemistry.
EDIT: Wow that image it huge...
mrkristofo
Well-Known Member
Here's a plausible mechanism for isomerization of humulone proposed by De Keukeleire. As it turns out, the ketone in the R-group is essential for isomerization. All the R-groups listed above contain a ketone.
https://www.homebrewtalk.com/wiki/images/3/34/Humulone-isomerization.png
https://www.homebrewtalk.com/wiki/images/3/34/Humulone-isomerization.png
A google books preview is availible here: Brewing: science and practice - Google Book Search
Fortunately, it's mostly there.
And if you're indifferent on the copyright stuff, the whole thing is hosted [ame="http://rapidshare.com/files/107178743/Brewing_Science_and_Practice__2004_.pdf"]here[/ame]
