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Brews & Views Bulletin Board Service * Brews and Views Archive 2009 * Archive through January 24, 2009 * Alpha acid isomerization < Previous Next >

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Denny Conn
Senior Member
Username: Denny

Post Number: 7119
Registered: 01-2001
Posted From: 75.145.77.185
Posted on Monday, January 12, 2009 - 08:26 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I have always read/been under the impression that certain "substances" in wort were necessary in order to isomerize the alpha acids in hops. Therefore I've always maintained that you can't make a "bittering tea" by boiling hops in water. My own tries at this have turned out a harsh, vegetal liquid that was so disgusting I never added it to beer. In a recent online discussion, a homebrewer maintained that not only does boiling hops in water isomerize the alpha acids, but on a tour of a Steiner hop facility in Germany he was told that they produce iso alpha extract by simply heating the hops themselves! I've never heard of that, but it made me realize that obviously iso extracts are made without boiling the hops in wort. So, does anyone know if alpha acids can be isomerized simply by heating? Can you really boil hops in water to get a "bittering tea"?
 

Bill Pierce
Moderator
Username: Billpierce

Post Number: 9827
Registered: 01-2002
Posted From: 24.150.192.193
Posted on Monday, January 12, 2009 - 08:57 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I am under the impression that alpha acid isomerization requires a pH of below about 6.0 and ideally around 5.0. I also thought it requires the relatively high temperature and physical agitation of boiling.

But as they say, then again, I could be wrong...
 

Denny Conn
Senior Member
Username: Denny

Post Number: 7120
Registered: 01-2001
Posted From: 75.106.192.58
Posted on Tuesday, January 13, 2009 - 12:54 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

But in that case, boiling hops in water of the correct pH should work. Yeah, I know what you mean about "could be wrong"....that's why I asked! Thanks, Bill.
 

Graham Cox
Senior Member
Username: T2driver

Post Number: 2050
Registered: 11-2004
Posted From: 68.32.253.156
Posted on Tuesday, January 13, 2009 - 05:33 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Denny, I call your attention to pages 209-211 of the "Handbook of Brewing," 2nd edition (edited by Priest and Stewart, a very serious tome of 853 pages) I'll wait while you thumb through your copy.

What? You don't have it? (I just got mine as a Christmas present.)

Here's a sort of summary presented in the book that relates to your question:

Factors encouraging faster isomerization:
* Higher wort pH
* Higher boil temperature
* Harder brewing liquor

Factors encouraging better retention of iso-alpha-acids, once formed:
* Lower wort gravity
* Higher wort pH
* Lower hopping rate
* Softer brewing liquor
* Higher adjunct ratio


Here are some pertinent facts presented:

The isomerization reaction is facilitated by the presence of hydroxyl ions; it would therefore logically follow that acidity diminishes the reaction. This agrees with the above "higher pH" bullets.

Calcium and magnesium promote isomerization. Without regard to other wort compounds present, it would seem that if you had sufficient calcium and magnesium present with enough carbonate to drive the pH up a bit, that would be ideal specifically for isomerization of iso-alpha-acids (my own assumption based on the facts presented.)

Man, this book is insane. The chapter on hops alone is 102 pages.

Regarding the flavor issues, the big thing that the book talks about is the loss of various compounds to trub, which is the major source of inefficiency, aside from the inherent inefficiency of the reaction itself. Since there is no trub in pure water, you're theoretically not losing anything that isn't insoluble in water. Maybe part of what you lose to the trub is actually beneficial from a flavor standpoint.

Anyhoo, the answer to your specific question appears to be "yes," so long as the water has a normal load of ions and isn't distilled, RO, etc.
 

Bill Pierce
Moderator
Username: Billpierce

Post Number: 9829
Registered: 01-2002
Posted From: 24.150.192.193
Posted on Tuesday, January 13, 2009 - 02:30 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Very interesting, Graham. Thanks for this information.

Jethro Gump's mantra comes to mind: "The more I know about beer, the more I realize I need to know about beer."
 

Hophead
Senior Member
Username: Hophead

Post Number: 2806
Registered: 03-2002
Posted From: 167.4.1.41
Posted on Tuesday, January 13, 2009 - 06:09 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

"Factors encouraging better retention of iso-alpha-acids, once formed:

* Lower hopping rate"

My head is spinning... Say it ain't so Charlie Brown.

I'll have to check around for this book, thx GC.
 

Denny Conn
Senior Member
Username: Denny

Post Number: 7122
Registered: 01-2001
Posted From: 63.114.138.2
Posted on Tuesday, January 13, 2009 - 07:46 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks for the info, Graham, but I think my 2 basic questions remain....can alpha acid be isomerized by heat alone? And will boiling hops in water isomerize the alpha acids? It seems like the answer to the latter is "likely" and the answer to the former is "unknown".
 

Paul Edwards
Senior Member
Username: Pedwards

Post Number: 1687
Registered: 03-2003
Posted From: 76.252.26.140
Posted on Tuesday, January 13, 2009 - 08:57 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

HH

Amazon.com has the book:

http://www.amazon.com/Handbook-Brewing-Second-Science-Technology/dp/082472657X/r ef=sr_1_4?ie=UTF8&s=books&qid=1231879826&sr=8-4
 

Tony Legge
Intermediate Member
Username: Boo_boo

Post Number: 410
Registered: 05-2005
Posted From: 72.139.4.145
Posted on Tuesday, January 13, 2009 - 11:07 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

From Dave Millers " The Complete Handbook of Home Brewing "...
Isomerize. To alter the arrangement-but not the kind of number-of atoms in a compound by heating or other means.

This doesn't say anything about boiling and even suggests, in my mind, chemically altering without heat. Boiling just makes the acids soluable afaik.
 

Denny Conn
Senior Member
Username: Denny

Post Number: 7124
Registered: 01-2001
Posted From: 75.106.192.39
Posted on Tuesday, January 13, 2009 - 11:26 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks, Tony.
 

Hophead
Senior Member
Username: Hophead

Post Number: 2807
Registered: 03-2002
Posted From: 167.4.1.41
Posted on Wednesday, January 14, 2009 - 12:15 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Holy Krap! 150 clams?? Must be some book! Thanks for info tho Paul... Maybe it's gold leaf... :-)
 

Denny Conn
Senior Member
Username: Denny

Post Number: 7125
Registered: 01-2001
Posted From: 75.106.192.56
Posted on Wednesday, January 14, 2009 - 01:24 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Knowledge is power....power is expensive!
 

Graham Cox
Senior Member
Username: T2driver

Post Number: 2051
Registered: 11-2004
Posted From: 68.32.253.156
Posted on Wednesday, January 14, 2009 - 04:59 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

"Boiling just makes the acids soluable afaik."

Actually, that's backwards. Isomerization occurs first, then the acids become soluble as a result. That's one of several reasons to boil your wort for at least sixty minutes.

Denny, as far as using heat only, I don't think that would do anything except to dry out, and evenutally combust, the hop material. Regarding the material I cited above - and I'm no expert, I'm just connecting some dots myself here - if isomerization is "facilitated by hydroxl ions" (OH-), there has to be some moisture of some kind present. More to follow on this point, but for our purposes as homebrewers, the most ready source of hydroxl ions is good ol' H2O. "Calcium and magnesium promote isomerization" - the most ready source of calcium and magnesium ions is - you guessed it - good ol' H2O.

Regarding methods of extraction of hop acids, the book in question cites many organic solvents that have been tried, to include "petroleum ether, methanol, ethanol, benzene, hexane, dichloromethane, and finally CO2 in liquid or supercritical form." CO2 is almost exclusively the method used today.

So, to answer your questions:

...can alpha acid be isomerized by heat alone? As far as I know, no.

And will boiling hops in water isomerize the alpha acids? Yes.
 

PaulK
Advanced Member
Username: Paulk

Post Number: 744
Registered: 02-2003
Posted From: 68.63.203.31
Posted on Wednesday, January 14, 2009 - 03:22 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Yes, you can isomerize hops (or at least kick off the process) in hot water alone. When I was in the Siebel course in Germany, they mentioned a process adopted by a number of breweries to reduce boil times. They would steep the bittering hops in a bucket of boiling water to isomerize the hops and then add it to the wort which would boil for as short as 20 minutes in some cases.
 

ChriSto
Intermediate Member
Username: Christo

Post Number: 500
Registered: 02-2006
Posted From: 216.176.226.154
Posted on Wednesday, January 14, 2009 - 05:21 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

They would steep the bittering hops in a bucket of boiling water to isomerize the hops and then add it to the wort which would boil for as short as 20 minutes in some cases.

The brewer at our local brewpub does something similar. He has done a number of on-the-fly "studies" on short-boil beers with water-isomerized hop teas added plus numerous wet-hop experiments, all in name of shortening each batch of brew to eke out every last drop from his IIRC 9 bbl system (he brewed close to 1500 bbl last year).

Gosh. 500 posts.

(Message edited by christo on January 14, 2009)
 

Denny Conn
Senior Member
Username: Denny

Post Number: 7126
Registered: 01-2001
Posted From: 140.211.82.4
Posted on Wednesday, January 14, 2009 - 05:22 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks for all the info, guys. I really appreciate it!
 

Tony Legge
Intermediate Member
Username: Boo_boo

Post Number: 412
Registered: 05-2005
Posted From: 72.139.4.145
Posted on Wednesday, January 14, 2009 - 09:15 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Actually, that's backwards. Isomerization occurs first, then the acids become soluble as a result.


Yes, I knew that, and should have said that in my statement.
 

Vance Barnes
Senior Member
Username: Vancebarnes

Post Number: 3554
Registered: 03-2003
Posted From: 74.7.7.66
Posted on Wednesday, January 14, 2009 - 10:51 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Just a little nit picking I know but there is not any Ca or Mg in H2O. There is in tap water but only hydrogen and oxygen in H2O.

If you're going to be all scientific, you've got to be scientific.
 

Kevin Kowalczyk
Intermediate Member
Username: Itsfunbrewingbeer

Post Number: 418
Registered: 10-2007
Posted From: 67.167.4.225
Posted on Thursday, January 15, 2009 - 02:39 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Vance, when I read that statement, I thought the same thing. Welcome to the nerd club, my friend.
 

Vance Barnes
Senior Member
Username: Vancebarnes

Post Number: 3558
Registered: 03-2003
Posted From: 74.7.7.66
Posted on Friday, January 16, 2009 - 05:57 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Welcome to the nerd club, my friend

Yea, too many chemistry classes I'm afraid. Or as one of my co-workers says, don't say it so someone can understand it. Say it so no one can possibly miss-understand it.