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Old 08-15-2013, 01:20 AM   #1
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Default Experiment - Ethanol humulone extraction

So I have done a search and a lot of the people I've seen posting about hop extracts seem to be trying to extract hop flavors and aromas from their hops to add to their beer.

While I personally wouldn't want to dump a bunch of grain alcohol into my fermented beer, I completely understand that, but the experiment I have been considering all day is this:

Alpha acids do not dissolve well in water. They are slightly soluble, and as they dissolve in boiling water, they convert to iso-alpha-acids. The conversion allows more alpha acids to dissolve in the water, which is why more time is needed to allow more to covert and more to dissolve. When I looked up the solubility of one alpha acid (humulone), however, it appears it is quite soluble in ethanol, and this is actually the main way they extract alpha acids from hops to make purified humulone (after further purification).

It seems alpha acid utilization starts to level out around 25%. I want to beat that. I am an organic chemist, and a 25% yeild is something that would get scoffed at in modern chemistry.

Therefore, here is my experiment:

1) Soak 0.25 oz medium alpha acid hops in a small amount grain alcohol for an extended period of time (like 1 week or something, or more, the longer, the better, I'd guess). Alpha acids are large molecules, so they will not dissipate like flavor and aroma molecules would. If I do several small extractions, like split batch sparging in an MLT, I'd say that'd be even better.

2) Shoots for 2 gallons of wort post-boil. Split into two 1 gallon batches.

3) Add ethanol hop extract to one gallon and bring to a boil. Let boil until it reaches 212, when I would assume all the ethanol to be gone. Boil for 2 hours

4) Bring gallon #2 to a boil and add 0.25 oz of same hops (from same bag) to the boil. Boil for 2 hours.

5) Add no flavor or aroma hops.

6) Ferment side by side, do everything the same, bottle, taste, see if extraction version comes out more bitter.

Theoretically, the ethanol should extract well over 25% of the alpha acids. Once the ethanol is gone from the boil, as long as I've stirred well enough to keep the alpha acids from scorching on the bottom of the pan, they should slowly convert into iso-alpha-acids, and I would expect to have a more bitter beer with the same amount of hops (therefore allowing for more efficient bittering later on, and more economical, if the hops are more expensive than the grain alcohol I end up using... either way, I'm a chemist, it's worth it for the learning to me).

What do ya'll think?

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Old 08-15-2013, 01:33 AM   #2
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I have had similar thoughts, but my train of thinking is to utilize alcohol extraction for the aroma flavor additions...I have no problem achieving bitter.

Not sure if this is possible...

I think the commercial hop extracts are done w/ CO2??? and perhaps vacuum...IDK, out of my area of expertise...

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Old 08-15-2013, 10:03 AM   #3
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I am going to revise my experiment some. I posted too early. I have decided to try to do something with bittering, aroma, flavor, and maybe even doing an extraction of double the amount and adding it continuously over the end of the boil. The issue I see with that is that the alpha acids will be dissolved either way, and the addition of the ethanol will likely add a lot more bitterness than flavor and aroma hops normally do. Maybe this is a way to shorten boils, though, if it works that way. I shall see.

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Old 08-15-2013, 04:30 PM   #4
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I use grain alcohol to extract hop oils from pellets for aroma in my low ABV "IPA" In a low ABV beer, there is not enough ethanol to extract the oils very well. I use a minimum of everclear and basically make a thick paste and let it set for just 1 hour and then I use this to "dry" hop with. Works great and adds only 0.3% ABV to the final product.

Now with alpha acids, you also have a solubility issue, but also an isomerization step as well.

What exactly is meant by 25% utilization? Where is the loss occurring? - this is the important question! If it were simply extraction of the alpha acids from the hop material, than one would think that using a more finely ground material would result in significantly better utilization, but it is less the 5% (whole vs pellets). This suggest there are losses that are occurring after the alpha acids are removed from the plant material. Further, boiling a lot longer does not result in significantly better utilization as one would predict if the isomerization rate alone were the key. Wort is a pretty complex mixture with all kinds of things to bind all forms of the alpha acids and reduce utilization. Somehow it is being lost post extraction. If this were not the case, if one only utilizes 25% per usage, then in theory one could re-use the hops again to extract more. This does not work.

I've messed with this a little bit with some success. Ethanol is a good solvent for alpha acids, but so is cooking oil. And 212F is good for isomerization, but 350F is really good! Sauteing hop pellets in cooking oil is a great way to extract and isomerize the alpha acids! The whole lot went into the boil kettle! I simply added some lecithin (equal volume) to emulsify the oil and had no problems with head retention.

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Old 08-15-2013, 05:01 PM   #5
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There is a nice write up here

Hops and hop products

Quote:
Isomerised hop pellets
The pellets for isomerised hop production are produced in a similar way to standard pellets (see Figure 3) with about 2% magnesium oxide added during the pelletising process. These “stabilised” pellets, packed in an inert atmosphere are heated to 50°C for approximately 14 days, when up to 99% of the alpha acids are isomerised in situ, giving wort utilisation rates of 80 to 90%, and final beer utilisation rates of up to 70% The handling and processing of isomerised pellets is similar to regular pellets. See Table 3.
So it appears that isomerization is pretty important, but there are still significant kettle losses.
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Old 08-16-2013, 12:29 AM   #6
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Holy moly! State College PA?! THAT'S WHERE I AM!



I will respond more later. I just got excited when I noticed that.

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Old 08-22-2013, 06:40 PM   #7
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Chemist here as well. Let me add my 2 cents because I have thought long and hard about maxing IBUs. Even adding extracts doesn't get you max IBU in the end. Also, hops are extracted with supercritical CO2 to keep freshness, not ethanol.

You have four major forces working against you that prevents maxing IBUs in beer. Keep in mind, IBU translates directly to iso-alpha acid concentration.

1 - Hop oils are volatile. My best guess to poor conversion (even with oil extracts) is that your oils are simultaneously isomerizing and being driven off during the boil. Oils float on top of water so they can easily be driven off in a boil before they isomerize.

2 - Thermal degradation. You boil and let the beer sit at room temp for at least 2 weeks so the iso-alphas are constantly degrading from the second they are created.

3 - Oxidation. It is hard to homebrew in inert atmosphere so you are losing iso-alphas to oxidation as well.

4 - Surface binding. Hop oils are well known to bind to surfaces so any precipitate will take some out and even your pots and carboys will bind too.

How do you get around this? Add isomerized alphas to your beer right before kegging / bottling so you can chill it and minimize degradation. This product already exists but you can DIY in a sneaky non-extract fashion.

Here is a trick that I have tried but I haven't been all scientifical about it yet so maybe you may be interested. I have done this three times but always to an IPA that is already bitter so I have never "validated" with a 0 IBU batch to see how well it works.

If you want to directly measure IBU, find the HPLC assay from ASBC because the UV based one isn't specific and goes to hell with dry hopping.

Put pellets in a tight sealing tube and purge with inert gas. Oven bake at 100C for an hour to isomerize. Dry hop with them and you will be giving your beer a late IBU boost that should max the soluble iso alphas. If the alphas isomerize, they will dissolve in the beer and no extractions are needed.

The best way to see if this works is to brew a beer with only late addition hops to minimize the IBUs. If the beer is bitter as F after dry hopping with isomerized pellets, then it works.

What I really want to try for a good control is a beer with no hops then add only baked hops as a dry hop perhaps in two separate additions a week apart. I just don't have time though!

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Old 08-24-2013, 01:43 AM   #8
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Wait... when you say ", MI" what part of MI do you mean? When I say that I mean....... I am a Michigan fan, not a PSU fan despite that grad school choice....


Despite all that... I can do this... Maybe not the HPLC... but maybe I can drive to undergrad and do all that. The HPLC's are pretty heavily used here at grad school.

I will do the test you suggest, but I will include a "normally bitter hopped" beer, though. Just for a normalization.

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Old 08-25-2013, 03:00 PM   #9
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Not sure if it helps, but I also tried making an ethanol hop extract using whole leaf hops, and found that longer is not better if you want good flavor. The resulting flavors I had were very vegetal. I've never repeated the experiment, so I don't know if that flavor was due to my pressing the hops to remove the extract or my leaving it in the everclear for 3-4 days (rather than, say, 30 minutes to two hours). At any rate, I prefer traditional hop usage, at least for flavor/aroma.

Oh, and I almost forgot to add that the ethanol seemed to have isomerized the alpha acids, because my hop extract was extremely bitter. No boil necessary.

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Old 08-25-2013, 06:51 PM   #10
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[QUOTE=nobeerinheaven;5458577..............
Oh, and I almost forgot to add that the ethanol seemed to have isomerized the alpha acids, because my hop extract was extremely bitter. No boil necessary.[/QUOTE]

This is probably not from isomerized alpha acids, but more likely from polyphenols in the hops. These taste bitter and can contribute to the perceived bitterness of a beer (beyond what the IBUs suggest - they don't count towards IBU #'s) The polyphenol levels vary from hop to hop, some add can add quite an extra "bitterness" when you dry hop with them.

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