# Dry Hop, Hop Creep, and D-Rest



## DazGore (11/11/19)

I have a few questions/theories regarding the above and would appreciate any insight.

With dry hopping, the general consensus was to dry Hop with 2-3 Plato left so that the yeast would devour any oxygen that was introduced. But, now with hop creep, is that necessary? As in, if the dry hopping starts a secondary fermentation, then surely that action would also consume any oxygen? 

So is it much better to ferment out totally, do a Diacetyl rest, and then dry hop? In which case, would you crash after the D-Rest, dump the yeast, then warm back up to dry hop? Or could you do a dump at fermentation temperatures.

Some research has shown a dry hopping of 72 hrs is enough to extract most of the flavour profile needed. My question is, if those hops do indeed start fermentation again, how long would the yeast need to devour those added sugars? And then you would need to do a Diacetyl rest on top of that secondary fermentation. So the 3 days hop soak should really be extended to 6-7, allowing enough time for extraction, fermentation and a D-Rest.... Thoughts?

Thanks
Daz


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## wide eyed and legless (11/11/19)

I have been reading something along a similar line, about oxygen and yeast, the yeast doesn't take up any oxygen as a result of dry hopping. From what I have read 14 hours after the start of fermentation the yeast do not take up more oxygen. Even the oxygen in the head space of a beer bottle which is widely believed by home brewers, is not taken up as the yeast secondary ferments the bottled beer.


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## MHB (11/11/19)

Hop flowers contain maybe 3-4% sugars, no surprise really sugars are how plants move nutrients around inside themselves so they can grow.
But seriously, adding 40g/L (920g in 23L) would be a ridiculously large dry hop addition, that would be at most 1.6g/L or an increase in the gravity of 1.00064, we cant measure that with anything available to home brewers.

Similar with Oxygen, yeast does consume O2, it will do so at any time when its alive, Oxidative products getting rearranged, other Oxidisation processes (sort of like oxidisation without Oxygen) do continue. To minimise these you have to go right back to the start of the brewing process (see LoDo brewing) and minimise the exposure to Oxygen right through the process. Paying attention to mash pH would help a lot to.

I cant see the amount of O2 being introduced by dry hopping being much of a matter for concern. If you are really worried you could cover the hops in de-aired water, then add the slurry to the brew, should reduce the O2 by a fair amount. But I strongly suspect there are lots of other places in your brewing process that would give was bigger returns on the time and effort.
Get the basics right work on the things you really can control and don't worry about minutia until you have everything else right (i.e. you are scoring 45/50+ for your beers) then start looking for the obscure.
Mark


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## DazGore (11/11/19)

Thanks for the replies thus far.

I am not worried, my processes are pretty good, I brew in SSBrewtech gear and everything is in a closed system.

I usually only worry about mash pH but will look at Pre Boil and Pre Fermenter pH as well to try and improve my beers. Currently I have a wheat beer that's at 4.6 pH so not too bad, but I could afford to be a couple of points lower.

I will also extend my 3 day dry hop to 5-7 to allow for any Diacetyl, not that I have had any problems with that, but no harm in doing so and I will continue to dry hop with 2-3 Plato left.


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## MHB (11/11/19)

Yep try for 4.1pH.
I wouldn't extend your fermentation nor allow extra Diacetyl rest, the amount of change the dry hops are going to make is miniscule. If you are getting a good clean ferment that's all over in 7-10 days, leave it alone, if not look at yeast population and health.
Remember that a Diacetyl rest is a remedial step usually done in lager brewing when you have a Diacetyl problem, if you are pitching enough healthy yeast into an Ale (inc Heffe) it shouldn't be necessary.
Mark


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## wide eyed and legless (11/11/19)

DazGore said:


> Thanks for the replies thus far.
> 
> I will also extend my 3 day dry hop to 5-7 to allow for any Diacetyl, not that I have had any problems with that, but no harm in doing so and I will continue to dry hop with 2-3 Plato left.



Before you do that Google Dry Hopping- Oregon State University.

Peter Wolfes Thesis
Here is a small extract.

2.3.3 Long Term Dry Hop Aroma Extraction
GC chromatograms were obtained for each sample (3 per treatment, 3 time points). Figure 5 shows the average concentration of linalool at days 1, 4, and 7. Figure 6 shows those same time points for the compounds myrcene. Surprisingly, extraction data did not show an increase in compound concentration over the time periods examined; in all cases the day 7 concentrations were either near the same level as day one (within standard deviation) or had fallen slightly. Final concentrations did not significantly differ between treatments, with the exception of geraniol.


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## DazGore (11/11/19)

Thanks for that, I will read it after this.

I have always only ever dry hopped for 3 days, as I had heard that you do not get much more utilisation after that.

My reasoning for perhaps extending to a 5-7 day soak is to allow the yeast to clean up after any secondary fermentation or hop creep that may of happened. Not to try and extract more flavour and/or aroma.

I suppose on a small scale home brew system it is maybe not that noticeable, but if I have the time, then why not wait a few extra days(?)


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## DazGore (11/11/19)

That was a interesting read, thanks for that.


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## wide eyed and legless (11/11/19)

DazGore said:


> That was a interesting read, thanks for that.


No worries, I have been doing quite a bit of dry hopping lately, link my snubby to another with the bagged hops in there already using a very aggressive yeast CN-36, 3 days transfer to the secondary, disturbing the yeast kicks it off again for a couple more days then two days cold crash so four days total dry hop.


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## razz (11/11/19)

wide eyed and legless said:


> No worries, I have been doing quite a bit of dry hopping lately, link my snubby to another with the bagged hops in there already using a very aggressive yeast CN-36, 3 days transfer to the secondary, disturbing the yeast kicks it off again for a couple more days then two days cold crash so four days total dry hop.


How does CN36 stack up against US05 WEAL?


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## wide eyed and legless (12/11/19)

I don't rate US05 that highly I did prefer SO4, but as US05 is the bigger seller the students from Monash Uni did a comparison test. I do know another retailer has re badged it Midlands Yeast I believe owing to its similarity to Nottingham yeast.


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## MHB (12/11/19)

What a pile of pseudo scientific crap!
Ok they have kept decent records but have missed a few fundamental steps.
Who are they - anything purportedly scientific will list authors/researchers.
Tilt Hydrometers? - were they calibrated, how, if we don't know, all the results are meaningless
Assumptions - paper is full of cause and effect statements without any substantiation...

I'm not even saying that the results are wrong, just object to advertisers (including WEAL) using "Fake Science" (fake news) to flog products.
The yeast from China might be good, but given the quality control issues common with Chinese products when it comes to brewing I would far rather invest an extra dollar in a known quality product.

WEAL, I think we all know your a big fan of Keg King, but I'm getting seriously sick of the constant product endorsements, thread bumping and outright advertising.
Can we get back to talking about brewing?
Mark


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## wide eyed and legless (12/11/19)

For a start I got my yeast direct from China some time ago, not through Keg King. Angel has been in the bread yeast business for over 30 years and only in the last 2 years into brewing yeast. I was curious to see how it performed and I did have my doubts that it would be any better than Fermentis S04. But for me I found it just as good as if not better than S 04 and will continue to use it.
Save a dollar (if it is cheaper) and give it a go you might like it.


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## goatchop41 (12/11/19)

I agree with Mark - that 'study' is absolute garbage, and I'm actually upset that I just spent 5-10 minutes of my life reading it.
Even if it were worthwhile in terms of methods, I would be hesitant to actually apply the results from it, considering that both beers were reportedly riddled with acetaldehyde and diacetyl.

As Mark mentioned above:
1) the amount of sugars that the hops add is minuscule, so this shouldn't really present an issue.
2) a d-rest in an ale should really not be required if you've taken care of yeast health and numbers prior to/during the ferment (obviously this is yeast dependent, but even in some of the high VDK producing English yeasts, you're fermenting at a high enough temp that a specific d-rest shouldn't be necessary, the clean up process should just happen itself). Add to this that good practice is to ramp ferment temp late in fermentation, which in itself will help with VDK clean up.

Someone having diacetyl issues after dry hopping should really be looking at what they are doing wrong prior to the dry hop, as they will be laying the groundwork for it then.


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## Reg Holt (12/11/19)

I don't see anything where it says that the test was supposed to be scientific, just a side by side test, a quick Google of Monash Brew Lab shows they are just students from Monash University with an interest in brewing. Nothing to get twisted knickers over.
https://www.monashbrewlab.com/


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## MHB (12/11/19)

Yep, both yeast/fermentation problems, makes you wonder if the testers really knew what they were doing.

Been having a think about "hop creep" my first thought is that its BS.
The amount of added sugar is I believe miniscule, I suppose its possible that hops contain Amylase that is converting some higher sugars into fermentable ones, that would result in a lower FG.
I suspect that after adding a heap of hops, some nit observed his airlock bubbling and assumed that the beer has started fermenting, rather than millions of nucleation points, causing some CO2 to come out of solution.

Been thinking about an experiment to test the possibilities, only problem is measuring the "effect". Best scales I have access to is only 0.1g makes getting significant results on small samples a bit of a pain.

Reg Holt - Sticking it on a Monash Letterhead and putting to together so it looks like a scientific paper (sort of)...
I don't think much of what they did in terms of being a useful comparison, what does get me in a bunch is whoring science to flog crap (not just in this instance).
Mark


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## chthon (12/11/19)

Why dry hop
Why dry hop (part two)
Why dry hop (part three)

Apparently, dry hopping can (will?) re-introduce diastatic enzymes into your beer. That is the real reason that fermentation can start again after dry hopping. It also probably depends on the hop species.


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## MHB (12/11/19)

I always find "shut up about Barclay Perkins" a bit perplexing (exasperating at times to).
The science of brewing has moved on a touch in the 120 odd years since the "Brewers Garden". Interesting that if you read part three, for Amylase in hops to convert dextrin's into sugars you would need to be blocking the tannin (polyphenols) in the hops, he used "Hide Finings" (shaved up bits of tanned leather), not something in wide use today.
If the tannin is not removed, the hops cant convert dextrin's to sugars so you get no extra fermentation.
Anyone adding shaved leather to their beer with their dry hops?
Mark


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## chthon (13/11/19)

Well, what about this one then?


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## DazGore (13/11/19)

https://www.rockstarbrewer.com/how-...n-beer-and-how-brewers-can-minimise-the-risk/

http://sea-brew.com/hop-creep-the-over-attenuation-experienced-when-dry-hopping/

Reading this, I wonder if you can denature the hop enzymes by bagging the hops and doing a sous vide at the temperature required to destroy the enzymes, before cooling and dry hopping.


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## MHB (13/11/19)

chthon said:


> Well, what about this one then?


Fair enough, Thomas Shellhammer is always worth reading, now anyone got the original paper? Its one I would like to read.
Mark


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## DazGore (13/11/19)

MHB said:


> Fair enough, Thomas Shellhammer is always worth reading, now anyone got the original paper? Its one I would like to read.
> Mark


I tried to get it, but you have to be a member or something. That's on the Oregan State University website.


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## MHB (13/11/19)

Me to, found it behind half a dozen paywalls. They want something like $30 USD to let me look at it, more to download...
(GOM mode) I remember when the whole idea of the internet was to share knowledge for free... bastards
Mark


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## Nullnvoid (13/11/19)

DazGore said:


> I tried to get it, but you have to be a member or something. That's on the Oregan State University website.



Link? I wonder if I can access it through work


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## goatchop41 (13/11/19)

MHB said:


> Fair enough, Thomas Shellhammer is always worth reading, now anyone got the original paper? Its one I would like to read.
> Mark



Ask, and ye shall receive


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## goatchop41 (13/11/19)

MHB said:


> I remember when the whole idea of the internet was to share knowledge for free... bastards



Google 'sci-hub' and thank me later


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## MHB (13/11/19)

Too Soon?
Thanks, will dive into the paper later but a quick scan it looks like it might answer a lot of questions.
Cheers Mark


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## Moog (13/11/19)

did you mean this thesis paper?


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## MHB (13/11/19)

Both good papers (at a quick glance), cant track down the one of the effects on beer FG caused by dry hopping (its the one behind the paywall) I think its this one: -
K. R. Kirkpatrick, T. H. Shellhammer, “Evidence of Dextrin Hydrolyzing Enzymes in Cascade Hops (Humulus lupulus)” Journal of Agricultural and Food Chemistry *66*, 9121−9126 (2018).

Cheers Mark


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## goatchop41 (14/11/19)

MHB said:


> Both good papers (at a quick glance), cant track down the one of the effects on beer FG caused by dry hopping (its the one behind the paywall) I think its this one: -
> K. R. Kirkpatrick, T. H. Shellhammer, “Evidence of Dextrin Hydrolyzing Enzymes in Cascade Hops (Humulus lupulus)” Journal of Agricultural and Food Chemistry *66*, 9121−9126 (2018).
> 
> Cheers Mark



Sci-hub delivers again


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## MHB (14/11/19)

Excellent thanks.
I tried searching Sci-hub for that paper but couldn't find it, have to spend some time learning how to use Sci-hub.
Thanks again
Mark


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## goatchop41 (14/11/19)

Reg Holt said:


> I don't see anything where it says that the test was supposed to be scientific, just a side by side test, a quick Google of Monash Brew Lab shows they are just students from Monash University with an interest in brewing. Nothing to get twisted knickers over.
> https://www.monashbrewlab.com/



Perhaps it was the fact that the whole thing is written up in the form of a scientific paper, with clear attempts (although not overly successful) at following scientific method, that gave us that impression? It is quite obvious when reading the 'report' that they've tried to angle it in that way.
The presentation of it clearly shows that it is intended to be seen as an attempt at scientific investigation/testing of the yeasts


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## goatchop41 (14/11/19)

MHB said:


> Excellent thanks.
> I tried searching Sci-hub for that paper but couldn't find it, have to spend some time learning how to use Sci-hub.
> Thanks again
> Mark



No worries.
Putting the whole reference (author, title, volume, etc.) in usually doesn't work for sci hub - a lot of the time you just need to put the title of the paper in.
Failing that, google the paper and find the 'doi' for it (the doi is usually easy to find if googling it gives you a result in NCBI - the doi will be in the NCBI web page), then input the doi in to sci-hub. That is guaranteed to work


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## wide eyed and legless (14/11/19)

Best place I have found for papers and books is this one.
https://www.academia.edu/
I downloaded Boulton & Quains book Brewing Yeast and Fermentation, for free normally would expect to pay $130 AU


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## goatchop41 (14/11/19)

wide eyed and legless said:


> Best place I have found for papers and books is this one.
> https://www.academia.edu/
> I downloaded Boulton & Quains book Brewing Yeast and Fermentation, for free normally would expect to pay $130 AU



That's a good one, cheers for that.
Library Genesis is also great for textbooks and other books. In saying that, if I download a book and it is good stuff, I am then more than happy to go and pay for it through legitimate means. This way just lets me actually see the full content of the book and work out if it is right for me.
Regarding the academic papers - academic journals are pretty scummy and make life hell for some researchers, so we shouldn't feel bad for getting those for free


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## TheWiggman (15/11/19)

DazGore said:


> I have a few questions/theories regarding the above and would appreciate any insight.
> 
> With dry hopping, the general consensus was to dry Hop with 2-3 Plato left so that the yeast would devour any oxygen that was introduced. But, now with hop creep, is that necessary? As in, if the dry hopping starts a secondary fermentation, then surely that action would also consume any oxygen?
> 
> ...



Sorry can't help but feel I need to address a few points here.
Where is the general consensus to dry hop before fermentation was finished to address oxygen? I've dry hopped before and after, and the general consensus I've read is to dry hop after it's finished so that fermentation doesn't take some hop aroma with it. Though to be honest I've never been blown away with the impact of dry hopping.
Re: sugars in the hops, I'm in line with Mark's thinking. As noted later the phenomenon of 'hop creep' isn't said to be due to the sugars in the hops.
As for the timing and diacetyl rest... what I would have said's been said.

All this has me wondering though - why are we talking about it? I've never heard to date anyone having an issue with dry hopping causing over-attenuation. Search back on this forum 15 years and nobody to my knowledge has opened a thread with "Dry hopped to buggery, exploding bottles / fizzy beer". There was one beer I recall where someone tipped about 1.5kg of hops into a 23l batch. I have this feeling that it's another botulism or HSA argument, that there are observable impacts from very high hop use at a clinical level but the net result for a home brew beer is SFA except in exceptional circumstances. I think I could do a lot more damage to a beer with poor technique than using too many hops (unless you don't like hops). In fact I'd argue don't use too many hops when dry hopping anyway because I've yet to be convinced that going hell-for-leather with dry hopping gets a good benefit for the dollars spent.


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## DazGore (15/11/19)

@TheWiggman I am trying to find the source for the dry hop timing. I guess I am basing it on a lot of things I have read, both from brewers of well known American breweries and the general homebrewing public.
A lot of it also stems from the hopping schedule of NEIPA's.
It is based on the theory that when you open your fermenting vessel to add the hops you are letting in oxygen. If the wort is still fermenting a cushion of CO2 is protecting the beer somewhat (debatable), but any oxygen that does enter along with the hops, would be devoured by the still active yeasts.
Yes, a lot of the dry hopping intention would still be stripped and carried away with the CO2, but some would still be obtained. And those that only whirlpool and not dry hop, their hopping is all subjected to the CO2 scrubbing affect. 
I have not experienced, to my knowledge, any of the so called hop creep, being higher alcol, extra fermentation, or higher volumes. But it seems to be a thing, seeing as a few breweries have noticed the impact and are taking precautions to avoid where and when they can.
Myself, I don't care if my 5.5% APA becomes 6.5%, that's a bonus as far as I'm concerned. I keg, so the volumes is not really an issue.
For me to add a couple of days to my beer after dry hopping to clean up any Diacetyl or secondary fermentation is not an issue.

Daz


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## goatchop41 (15/11/19)

TheWiggman said:


> Where is the general consensus to dry hop before fermentation was finished to address oxygen? I've dry hopped before and after, and the general consensus I've read is to dry hop after it's finished so that fermentation doesn't take some hop aroma with it. Though to be honest I've never been blown away with the impact of dry hopping.



On a personal anecdote level, I think that the whole 'fermentation will blow off hop aroma' thing is bullshit, and is just some theoretical bollocks that gets repeatedly regurgitated without any substantiation.
When I make a NEIPA/hazy beer nowadays, I pretty much only dry hop when I pitch the yeast. From my anecdotal experience, not only does this get me great, persistent haze, but the dry hop character is just as pronounced as it is when I do conventionally timed dry hopping, or even double dry hopping (one at pitching and one at the end of fermentation)


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## DazGore (16/11/19)

Here is a .pdf of Oregon University's research on dry hopping, hop creep, sensory analysis of various hops, etc...


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## wide eyed and legless (16/11/19)

I can't see there being that much sugar in hop flowers, the carbohydrates produced by the leaves will go into the root system for growth energy, and as they are wind pollinated they don't need nectar to attract bees. I would say the best access to any sugar reserves would be through the new shoots, probably why the Romans used to eat them.



DazGore said:


> If the wort is still fermenting a cushion of CO2 is protecting the beer somewhat (debatable), but any oxygen that does enter along with the hops, would be devoured by the still active yeasts.


As I said earlier,once yeast are anaerobic respiration going around mopping up oxygen is not on the yeasts agenda.


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