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-   -   Leaf Hop Absorption Measured (http://www.homebrewtalk.com/f12/leaf-hop-absorption-measured-241469/)

ChemE 04-22-2011 11:27 PM

Leaf Hop Absorption Measured
 
I have searched this topic several times over the last three years and I've always been shocked and disappointed with the lack of careful measurement regarding this topic. I'm brewing a barleywine tomorrow with an OG of 1.120 and five ounces of whole leaf hops (it's just a 3 gallon batch) so I'm very interested in how much of my precious barleywine those pesky hops are going to drink up.

I decided to conduct a simple stove-top experiment to get a number. 0.39 ounces of 2008 cascade hops sacrificed themselves for our collective knowledge. Below is the simple setup consisting of a hop bag, the cascade hops, a small pot of water, and of course a gram scale.

Experimental Setup
http://www.homebrewtalk.com/members/...3583-setup.jpg

I wanted to make the amount of water that the hop bag absorbed a non-issue, so I soaked it in the boiling water for a minute and then hung it by its drawstring for two minutes to allow it to drain. This is how I drain my hops over the boil kettle while I chill. The damp/wet hop bag had a mass of 28 grams.

Wet/Damp Hop Bag Being Weighed
http://www.homebrewtalk.com/members/...et-hop-bag.jpg

Next step was to add the hops (but not the oxygen absorber!) and boil for 20 minutes. I assume this is long enough for them to absorb what they can but this is an assumption. After their boil, I hung the bag from the drawstring again for two minutes to simulate draining over the boil kettle. I did not squeeze the bag since it is claimed that this extracts tannins (another theory which wants to be tested).

Hops Being Drained for Two Minutes via Gravity
http://www.homebrewtalk.com/members/...ining-hops.jpg

Wet/Damp Hops Being Weighed
http://www.homebrewtalk.com/members/...5-wet-hops.jpg

So, the final mass is 93 grams less the 28 grams for the wet hop bag and less 11.1 grams for the dry hops yields a mass increase due to water absorption of 54 grams. Scaling this up from 0.39 ounces of hops to a full ounce takes us to 138.3 grams of water gain or 138.3 mL of water absorbed. The converts to 0.146 quarts of water per ounce of whole leaf hops. My data appears below.

Data and Calculations
http://www.homebrewtalk.com/members/.../3581-data.png

Some assumptions and sources of error:
1) I assume that 20 minutes is sufficient to completely hydrate the hops
2) I assume that tap water goes into the hops just as readily as sweet wort
3) I assume that the specific gravity of the water that went into the hops is 1.00
4) All weights taken on a gram scale so precision could be higher

I think these assumptions are safe and the source of error minimal. Overall I trust this number but certainly welcome feedback or suggestions. I hope the community finds this useful.

shauntraxler 04-23-2011 07:29 AM

Seems solid to me. Nice write-up.

Dogphish 04-23-2011 12:16 PM

i don't think that squeezing the hops will extract tannins. i believe that only the grains have tannins that you should worry about. i asked that exact question on this forum before, and that was the general consensus.

cjb 04-23-2011 09:48 PM

Quote:

Originally Posted by Dogphish (Post 2862423)
i don't think that squeezing the hops will extract tannins. i believe that only the grains have tannins that you should worry about. i asked that exact question on this forum before, and that was the general consensus.

Yeah, I had the same misconception, based on warnings against squeezing the grain bag. Asked on another forum, and was told it's not an issue for hops.

timbudtwo 04-23-2011 10:03 PM

Quote:

Originally Posted by Dogphish (Post 2862423)
i don't think that squeezing the hops will extract tannins. i believe that only the grains have tannins that you should worry about. i asked that exact question on this forum before, and that was the general consensus.

You can squeeze grains too. It doesn't release tannins, high temperatures do. That was an old brewers-wife tale.

http://www.homebrewtalk.com/f36/do-y...g-biab-177051/

ChemE 04-23-2011 10:55 PM

Hmm, now I wish I had gone a step further and wrung the heck out of the hop bag after I let it gravity drain. I'll perform that measurement next week when I get back in town (business travel).

itoriapt 10-29-2012 01:14 AM

Nice work, good sir

Dirty25 10-29-2012 06:08 PM

I would have thought they absorbed more than that. Last time I dry hoped 3oz of leaf hops I swear I lost a half gallon. Great work for figuring this all out..

ChrisNH 12-29-2012 04:47 PM

Came across this thread and had to chime in that while this experiment seems valid my anecdotal evidence suggests a lot more absorption.

Perhaps some confounding factors are:

1. Dryness of the hops.
2. Integrity of the hop (does a whole bud absorb more then a shredded bud?)
3. The impact of the boil process
4. The total volume of the mass vs time left to drip.

I do know that no matter how well I try to drain, when I come back to the kettle to dump and clean later more wort has magically appeared which tells me "time to drip" is probably a significant factor. I don't like to leave things exposed for a long time during the vulnerable stage of the wort.

Regards,

Chris

Denny 12-29-2012 06:51 PM

Quote:

Originally Posted by timbudtwo (Post 2863505)
You can squeeze grains too. It doesn't release tannins, high temperatures do. That was an old brewers-wife tale.

http://www.homebrewtalk.com/f36/do-y...g-biab-177051/

No, high pH extracts tannins. Nothing wrong with high temps if your pH is OK. How would people do decoctions otherwise?


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