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Leaf Hop Absorption Measured

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ChemE

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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


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


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


Wet/Damp Hops Being Weighed


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


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.
 

Dogphish

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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

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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

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ChemE

ChemE

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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).
 

Dirty25

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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

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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

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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
I agree. I account for whole hops to absorb 12 oz. of wort for every oz. of hops and I find that quite accurate.
 
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ChemE

ChemE

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Denny, I don't know how an ounce of hops could absorb that much liquid unless it didn't have any time to drain at all.
 

Denny

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Denny, I don't know how an ounce of hops could absorb that much liquid unless it didn't have any time to drain at all.
It's a figure I saw many years ago. I adopted it and it's been pretty accurate for me. I generally do little to no draining of the hops, though.
 

ChrisNH

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I agree. I account for whole hops to absorb 12 oz. of wort for every oz. of hops and I find that quite accurate.
Thanks, I will start with that assumption. I am going to pay more attention to my losses in upcoming beers and try to get a better feel for whats happening in my kettle. I have just added a valve to my kettle after dumping through a colander for years and that has made me look more closely at my assumptions about where my losses are coming from.
 

Kaiser

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Thanks for running this experiment.

What's needed now is more experiments like this, or close observation on brew day to establish how much this number varies. I think it should be pretty simple to keep track of the wet weight if a hop sack is used.

Kai
 

HawksBrewer

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I agree. I account for whole hops to absorb 12 oz. of wort for every oz. of hops and I find that quite accurate.
I have to agree with a number similar to that, especially w/ dryhopping. I brewed a 10 gal batch of APA w/ 26 oz of hops and ended up bottling only around 65-70 beers, having lost 3.5 gals or so to hops in either the boil or primary/secondary. When I did the math I think the number was something around 12-15oz of wort/beer lost for every oz of hops.
 
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ChemE

ChemE

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Thanks for running this experiment.

What's needed now is more experiments like this, or close observation on brew day to establish how much this number varies. I think it should be pretty simple to keep track of the wet weight if a hop sack is used.

Kai
My pleasure Kai. I would like to see others replicate this too. If I lost 12 ounces of finished beer per ounce I would sanitize a laundry mangle or something!!!
 

Denny

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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.
Nope, hops have tannins, too.
 

Kaiser

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I brewed an IPA^2 with my home grown whole leaf hops last night. To see how much wort gets absorbed by the hops and some trub I let them drain in a funnel with screen. I used that set-up to recover wort for later yeast propagation.

The 120g (4 oz) hops that I started with weighed about 990 g once allowed to drain. This is an absorption of about 7.3 oz wort per oz dry hops. Or 200 ml/oz (ChemE, you should stick with SI or US units).

I did have some trub in these hops which does absorb a considerable amount of wort and could be the cause for the higher number. But trub will always be present in practice. The amount will depend on the grist or if extract was used. In this case most of the hot break went into the fermenter, though.

Kai
 

RichBenn

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I'm willing to bet when using hops in a bag that the amount of remaining water vs. weight of hops is not linear; that is, you may get a different water/hop ratio in a bag with more hops than in a smaller sample.

Whether this is significant compared to the other variables at play, I can't say. Another experiment(sigh...).

What I will say is that I squeeze my hop bags (used in the boil) with a spoon against the side of the kettle. The technique seems most effective for certain amounts (5 oz or so) of hops, due to the size of the spoon and bag. I haven't weighed the leftover hops yet, but my final fermentor volumes suggest it's fairly effective. All that hop juice is too good to pass on for highly hopped IPAs and IIPAs, IMHO.

I do aplaud your efforts to get a handle on this topic, as no doubt many have pondered the question. Whatever your hopping/straining/transfer method, knowing what you have at the end is important for recipe adjustment.
 
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ChemE

ChemE

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ChemE, you should stick with SI or US units
Meh, I'm more comfortable with grams than ounces for expressing small masses that's why I mix units freely. Also, chemical engineers tend to get pretty comfortable with both metric and Imperial. Point well taken though, I know some aren't comfortable converting between the two. Interesting about the trub though. Obviously my simple initial experiment didn't have any break material to confound the result.
 

Kaiser

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The missed mars once b/c of mixing unit systems :)

I'm obviously not as tied to the imperial system but I see that it works pretty well for most things here in the US.

Brewer's Friend has hop absorption set to 5 ml/g I don't know where this number came from and it may also be for pellet hops.

Kai
 

kingwood-kid

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Inspired partly by this thread, I got roughly 4:1 the one time I weighed with pellet hops. This was assuming a 5G paint strainer bag weighed nothing and absorbed no water, which I suppose could be considered a source of error. Since the dry weight of the hops was 6oz, I didn't feel that weighing the bag would greatly change the results.
 
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ChemE

ChemE

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The missed mars once b/c of mixing unit systems :)

I'm obviously not as tied to the imperial system but I see that it works pretty well for most things here in the US.

Brewer's Friend has hop absorption set to 5 ml/g I don't know where this number came from and it may also be for pellet hops.

Kai
Yup, that was a classic engineering blunder to be sure! BIG difference between m/s and ft/s when it comes to landing on the surface of a planet!

So 5 ml/g wort/beer absorption translates into 4.8 fluid ounces per ounce of hops. My initial result was 4.68 fluid ounces per ounce of hops. I would call that some pretty darn good agreement.
 

Kaiser

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I didn't realize that a fl oz of water doesn't weight an oz.

Let's abandon the use Imperial measurements for any scientific work right here :)

Kai
 
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ChemE

ChemE

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I didn't realize that a fl oz of water doesn't weight an oz.

Let's abandon the use Imperial measurements for any scientific work right here :)

Kai
:) Indeed. A fluid ounce is 29.5735 mL and an ounce is 28.375 g.
 

SOB_OCDAVE

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Just wanted to add my .02 cents. I made an IPA last night (7/20/14) and used 7 oz of dried whole leaf hops that I ordered from Hopsdirect.com in 1 lb bags. They are very dry and absorbed a significant amount of wort. To be more specific, my recipe was for 5.5 gal and my preboil volume was 7 gal. I assume an evaporation rate of 10% per hour. I decided on a 90 min boil and continuous hop additions every 10 min for 60 min. My final volume in my site glass said 5.5 gallons but once the kettle was drained I was a whole gallon shy of my 5.5 gallon mark! I lost 1 gallon of wort to 7 oz of whole dried leaf hops.

My only thoughts on combating this for future boils is to weigh out my hop additions and soak them in boiled water and add to the boil presoaked.
 

droshi

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Not sure if anyone recommended. But I grind all my whole leaf hops in a blender. For me, grinding all hops, spices and pretty much anything used in the boil helps to settle it down to the bottom much better during a 20m+ whirlpool. It also helps for the mentioned water absorption problem where I can get a lot more clear liquid from a batch. 5.5g final boil volume gets me 5g of clear wort.

I do the same with dry-hopping, but since I do this in a keg I drop the ground hops into a muslin bag and use dental floss to tie it to the handle.
 
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jonkranked

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hi guys, there's some good info for me in this thread - as i'm just now going to be using whole hops for the first time. i'm actually growing my own hops (chinook, cascade, & 2 x centennial). since they are first year plants i'm only going to use them for dry hopping in secondary fermentation. for a variety of reasons (timing mostly) i'm going to have to dry some of them., but am also hoping to use some of them fresh. as far as i can tell, OP's measurements were used with dry hops, correct? Obvsiously fresh hops will not absorb as much moisture, has anyone ever measured how much (if any) water is absorbed by fresh hops?
 

ibrew92

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I made some measurements a few years ago and am closer to Denny's figure:
whole hops 9.9 oz wort
pellet hops 6.7 oz wort
 

stz

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I use 1:1 for ease in recipe planning but have found 1.1-1.2:1 (liquid:hops) to be more typical in practice.
 
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