"Isomerization" in Hops???

Hey everyone, can you take a look into this thread and let me know what you think about the idea of the volume of water changing the isomerization of hop compounds. I don't see how the volume of water would be able to variably switch around isomers. Maybe someone can help clear this up.

https://www.homebrewtalk.com/f39/partial-boil-vs-full-boil-139704/

It is not the volume of water that affects hop utilization, but the concentration of dissolved sugars in that water. Basically hop utilization in the boil (isomerization) is inversely proportional to the gravity of the boil. So a more diluted wort (full boil) increases hop utilization.. A more concentrated wort (partial boil) will require more hops for the same effect.

...or this is my understanding

jbbeer said:

It is not the volume of water that affects hop utilization, but the concentration of dissolved sugars in that water. Basically hop utilization in the boil (isomerization) is inversely proportional to the gravity of the boil. So a more diluted wort (full boil) increases hop utilization.. A more concentrated wort (partial boil) will require more hops for the same effect.

...or this is my understanding

Click to expand...

what he said

Cool, that makes sense...not to get caught up in the semantics of the issue, but im nearly positive that 'isomerization' does not have the same meaning as "utilization." Isomer refers to molecules with the same atomic contents but either with a different connectivity or structural layout (such as eclipsed or gause). So why are people throwing around the word? Not to be dogmatic about it or anything...

The degree of hop acid utilization is proportional to how much of the total amount of acids are isomerized. So they are related, but not equivalent.

Also, on the original topic, I believe it is the concentration of proteins in the wort that affect isomerization/utilization rather than the sugars. I heard this on Brew Strong, and they explained that as the proteins coagulate and drop out of suspension, they take some of the hop acids with them, decreasing the total amount available for isomerization.

-Steve

jbbeer said:

It is not the volume of water that affects hop utilization, but the concentration of dissolved sugars in that water. Basically hop utilization in the boil (isomerization) is inversely proportional to the gravity of the boil. So a more diluted wort (full boil) increases hop utilization.. A more concentrated wort (partial boil) will require more hops for the same effect.

Click to expand...

Actually this was disproven a while back. Hop utilization has no direct correlation to wort gravity, but utilization is impacted by break material which carries iso-apha acids out of suspension. John Palmer reported on this a couple years ago.

Protein coagulation could trap some of the acid molecules contributing to the bitterness (and heat is a known source of coagulation), but my point is that 'isomerization' does not make sense. You don't "isomerize" a molecule like you "utilize" a molecule. Molecules exist as one isomer or another isomer, some molecules have the ability to have more than 2 isomers based on the general equation # of isomers = 4N+2where N is the number of chiral centers for the molecule. The amount of water or the sugar concentration will not start flipping isomers. I know how the amount of water changes hop utilization...but why is John Palmer making any regards to isomers?

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

i just don't see how water and sugars are flipping isomers. Considering the compounds comprising alpha acids are naturally occurring in hops, chances are they are pretty stable. Water is obviously very stable, and sugars are typically very stable. So if we are dealing with 3 relatively low energy molecules without a tendency to be very reactive, even with the input of heat, why would we start changing around the isomers? Also, can anyone find an image of the molecular structure of an alpha acid? This would help solve the issue...if its not a chiral molecule this discussion will change pretty quickly.

hmmm i question why i ask all these questions....i love hops

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

I'm no chemist, but this guy is: http://homebrewandchemistry.blogspot.com/2007/02/hop-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

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!

SavageSteve said:

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

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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?

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.

ColumbusAmongus said:

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.

Click to expand...

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.

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.