"Isomerization" in Hops??? - Page 2 - Home Brew Forums
Home Brew Forums > Home Brewing Beer > Brew Science > "Isomerization" in Hops???

Reply
 
Thread Tools
Old 10-03-2009, 10:00 PM   #11
Edcculus
Recipes 
 
Jun 2007
Greenville, SC
Posts: 4,546
Liked 48 Times on 45 Posts


Here is what wikipedia has to say about the molecular structures of different essential oils found in hops

Humulene
Myrcene
Caryophyllene
Farnesene

I believe we are only interested in humulene

 
Reply With Quote
Old 10-03-2009, 11:43 PM   #12
SavageSteve
 
SavageSteve's Avatar
Recipes 
 
Sep 2007
Connecticut
Posts: 987
Liked 9 Times on 6 Posts


I'm no chemist, but this guy is: http://homebrewandchemistry.blogspot...chemistry.html

He has a diagram of a possible way in which the alpha acids are isomerized. I have no idea if he's right or wrong.

-Steve
__________________
On Deck: Jamil's Vanilla Robust Porter
Fermenting: Orange Blossom Mead
Kegs: Element 56 Pale Ale, Ron's Belgian Blonde, Summer'n Saison, Furloughktoberfest '09, Grateful Pale Ale, Sam Adams Cream Stout Clone, EdWort's Apfelwein
Planning: n/a

 
Reply With Quote
Old 10-03-2009, 11:51 PM   #13
shot0rum247
Recipes 
 
Feb 2005
Charlottesville, VA
Posts: 250
Liked 1 Times on 1 Posts


AH! that explains so very much about "alpha acids". That's pretty cool, good find! (I study organic chemistry...so that speaks to me :-)) thanks a lot!

 
Reply With Quote
Old 01-07-2014, 03:35 AM   #14
RobertRGeorge
Recipes 
 
Jul 2012
Nelson, Bc
Posts: 537
Liked 49 Times on 39 Posts


Quote:
Originally Posted by SavageSteve View Post
It's the isomerization that creates the bitterness-- converting one isomer of a hop acid into another. For a given amount of hop acids in the boil, the percentage that get isomerized is your utilization.

-Steve
Picking up on an old thread to understand the effect of isomerization. From what I read, the bitterness contribution to beer depends on boiling the hops so that the alpha acids are "isomerized" and the bitterness develops over time even though the alpha acids dissolve almost immediately.

I have tasted raw hops and they taste pretty bitter to me. Does the boiling then make the taste *more* bitter because the molecular structure has been altered?

 
Reply With Quote
Old 01-07-2014, 01:23 PM   #15
ColumbusAmongus
Recipes 
 
Feb 2011
, MI
Posts: 178
Liked 4 Times on 4 Posts


It isn't necessarily isomerization…it is dissolution that is the problem. Isomerized alpha acid have a low solubility in water. If you do partial boils, and then dilute up to 5 gallons, you are limiting the amount of solubilized iso-alpha acids in your final volume which directly relates to IBUs.

The IBU measurement IS the concentration of isomerized alpha acids. I forget what it is specifically but it is something like 1 IBU = 1mg/L of alpha acids. As people well know, there is a cap of IBU around ~100 give or take so 100 mg/L is the maximum solubility of alpha acids.

Here is a fun math experiment for everyone. The golden equation for dilutions is C1V1 = C2V2.

Lets say that you do a 1 gal boil and use 20 oz of hops at 60 minuts. Your max IBU for that 1 gallon is 100 lets say (what ever the cap is). What does your final (theoretical) IBU come out to when you dilute?

C1=100 IBU
V1 = 1 Gallon
C2 = ? IBU
V2 = 5 Gallon

C2 = C1*V1 / V2 = 100*1 / 5 = 20 IBU


One thing that I have thought about for a while is the isomerization. It is well known to happen over temps of 100C so if you are boiling water for an hour, you should be creating more than 100 IBUs worth of isomerized alpha acids. Where do the others go? They have to evaporate off. Anything that doesn't dissolve in the water will be an oil floating at the top of the wort and is most likely being evaporated off. This is probably important to note because it will really impact partial boils. You are most likely converting more than plenty of alpha acids over but you are in turn just boiling them off.


 
Reply With Quote
Old 01-11-2014, 03:02 AM   #16
LordUlrich
Recipes 
 
Dec 2010
Rochester, MN
Posts: 540
Liked 12 Times on 11 Posts


Quote:
Originally Posted by ColumbusAmongus View Post
One thing that I have thought about for a while is the isomerization. It is well known to happen over temps of 100C so if you are boiling water for an hour, you should be creating more than 100 IBUs worth of isomerized alpha acids. Where do the others go? They have to evaporate off. Anything that doesn't dissolve in the water will be an oil floating at the top of the wort and is most likely being evaporated off. This is probably important to note because it will really impact partial boils. You are most likely converting more than plenty of alpha acids over but you are in turn just boiling them off.

My understanding is that the conversion will slow as the max solubility is approached.
Another factor which plays into hop usage in a partial boils is that as you approach the 100 IBU limit, you need exponentially more hops to get another IBU.
__________________
Don't take any more faith in anything I say than you would anyone else on the internet. If you listen to what I say, then hurt your self or break something it is your own fault, I am just expressing my opinion or experience.
THINK for your self!!

 
Reply With Quote
Old 01-18-2014, 01:33 PM   #17
MaltyHops
Recipes 
 
Nov 2011
Adelaide, South Australia
Posts: 42
Liked 2 Times on 2 Posts


Any thoughts to what happens the other way?

Eg. suppose you manage to max out at the ~100IBU level and continue boiling so the wort volume decreases through evaporation. Then either solubilized iso-alpha acids remain in solution and break through the 100IBU barrier, or they start to precipitate to maintain the 100IBU barrier?

Hops for thought.

 
Reply With Quote


Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
"American" or "Imperial" Oatmeal Stout Recipe: Critiques please! cladinshadows Recipes/Ingredients 5 11-23-2015 11:14 PM
Anybody ever heard of "Golden Hops" Humulus lupulus Aureus? heavysteve Hops Growing 21 05-01-2012 06:47 PM
"Boil The Hops, Not The Malt Extract" By: Steve Bader gunnyg Extract Brewing 32 02-12-2011 10:33 PM
Hops: Bitterness "flavor" on long boils; explained Denny's Evil Concoctions Recipes/Ingredients 11 03-07-2008 04:40 AM


Forum Jump