Interesting bit of research published just a few days ago: https://pubs.acs.org/doi/10.1021/acs.jafc.8b03563
TL;DR - dry hopping may decrease your final gravity.
Cheers,
g
No, it was first published between 1939-41. We talked about it on Experimental Brewing a couple years ago. Here’s a link to the show and the original paper…Episode 12 – Going Stale | Experimental Brewing
And the effect was observed and utilized long before that, if not fully understood (though by the late 19th century, diastase was known to be responsible.) It was the primary reason for dry hopping in the 19th century, along with providing tannins to precipitate proteins, which together biologically and physically stabilized beer.
That’s really interesting. The Scientific American article I read about this in was the result of some issues Allagash was having with high pressures in bottle-aged dry-hopped beers. Beer Fermentation Hops Along | Scientific American (there’s a transcript available)
Funny that this was a big ‘mystery’ to the guys at Allagash, and is apparently hip-pocket knowledge among the homebrewers!
Guess they ought to listen to Experimental Brewing! 
Just this weekend I was reading through some old blog posts of Ron Pattinson’s, and found excerpts from an extensive paper on this from the Brewer’s Guardian in 1893. It doesn’t seem much has been added to the subject since then!
Good to know, I’m going to try dry hopping for the first time ever. Lol!
It’s not an issue unless you’re dry hopping at extremely high levels.
Disagree. A little dab did me.
Yer gonna have to convince me it Was the hops since science and testing says otherwise. How many times has it happened? What makes you relate it to dry hops?
Again?! I might be unable to convince you, but can’t see why my experience is unconvincing just because it’s not “sciency” enough. Here it is once again:
Key things to stress: “stalled for 22 days!”, then added dry hops, then SG finally fell from 1.019 to 1.013. There was friggin no activity at all for 22 days. (The only reason I waited so long to dry hop is that I was out of state on vacation – checked gravity before and after vacation.)
How much hops did you add? Has it happened more than once? How can you track it to disaster in the hops?
I believe his point is that fermentation was stable for several weeks, until the 0.67 oz of dry hops were added.
My question on this is: The typical advice for drinking hoppy beers, commercial or homebrew, has been to drink them as fresh as possible to avoid “freshness” (aroma, flavor, whatever). How much of that issue is due to aging/oxidizing hop compounds vs. change in the beer related to these enzymes? I imagine that’d be more of an issue for packaged beer.
What if it was introduction of a small amount of oxygen when you dry-hopped that ‘re-stimulated’ fermentation?
Thank you for your support, sir. You get it.
It is clear to me is that a dry hopped beer will tend to evolve with age. However there continues to be a lot of variables at play. Is this evolution due more to oxidation, or enzymes, or both, or something else? The greater question I would have: Has the brewer allowed the dry hop enzymes to finish doing their thing prior to packaging, or did they immediately package the beer before the enzymes could take effect and then expect you to drink it all up within a week of packaging, or not, or what? In my case, I left the beer in secondary long after I dry hopped, until Final-Final Gravity of 1.013 was reached. This took a long time actually, 17 days after dry hopping to be precise! I think most brewers out there would be hesitant to dry hop for as long as I did prior to consumption, which indicates to me that evolution IN THE PACKAGE is happening all over the dang place, and might very well be the true reason why people say “drink it fresh!” based on flavor impacts, without fully understanding why we should drink it that fresh or how fast the “freshness” disappears. I don’t know if people understand or will ever agree upon the definition of “fresh”… to some perhaps this means “within the first 17 days of dry hopping” or of packaging??? Can the exact number of days be quanitified and agreed upon by all brewers?! Good luck with that! And so what if they wait longer than 17 days or whatever… is the beer just drier / lower gravity / more attenuated at that point than the brewer intended? Or is there some other biotransformation or oxidation going on? And does this continue far beyond the first 17 days or whatever?! Gosh, I don’t know, I don’t have all the answers, and I really don’t think ANYONE does or ever will! Very few if any folks today understand very well what’s all going on when they dry hop, and what “freshness” really means and whether and why it matters, IF it matters. We all have a lot more to learn. Few have run any extensive experiments on dry hopping to know what process they like best, why they like it best, and how much it matters. We all just have a tendency to do whatever the “experts” do without question and without our own experience to form our own opinions. I’m still learning too. I only have this one experience to go by so far… but it was an accidental eureka moment for me, I was like hey wait a minute… why should dry hopping unstick a stuck fermentation… and this one experience I’ve had might still be infinitely better than the zero experience that many others have who will argue tooth & nail that they’ve got all the answers when really they have nothing but what someone else told them.
But anyway. Sorry if this sounds ranty… it just kind of all spilled out in an ugly disorganized manner, and I’m too busy today to edit it… so… there you go, take it or ignore it, it honestly doesn’t matter as much to me as it might sound.
Cheers all.
That, I think, is a very real possibility as well. Who knows. I haven’t placed samples into a gas chromatograph since college… that was a looooooooooooooong time ago. Nor a DO meter, if such a thing exists (I am guessing it does?!).
Yes, but there is no evidence that it was diastase in the hops that did it. This is a data point. As such, a single instance only provides material for further study, not a conclusion. Given that I haven’t seen any other reports of such a small amount of dry hops having this effect, I can’t take this as even close to conclusive. It’s like saying “I danced in my front yard to keep flying elephants away and I haven’t seen any flying elephants, so it must work”.
Not to put words in Denny’s mouth, but I think the point he may be that while indeed you did notice resumption of a stuck fermentation after adding the dry hop charge, you cannot definitively say that it was due to enzymatic activity from the hops. Now the converse is also true - you cannot definitively say it did not happen because of hop enzymes. The point is, correlation doesn’t equal causation.
I’m inclined to believe as already stated that it could have been a combination of factors that caused your fermentation to resume - oxygen ingress, the yeast being slightly shaken up due to the hop addition, enzymes in the hops, and even potentially microbial contributions from the hops themselves (while hops have antimicrobial properties, they are not sterile). However, short of doing a proper fully controlled experiment with tons of replicates for statistical power (which almost none of us are doing), we can’t know for sure.
Exactly!
Maybe not by us, but experiments have been done, though seemingly forgotten and the wheel now being reinvented. The 1893 paper I mentioned above controlled for and ruled out microbial contributions, simple rousing or oxygen introduction, and sugars native to the hops themselves. They further found that dry hops, in 7 days in beer, produced diastatically from non-fermentable carbohydrates 68.7% their own weight (!) in fermentable sugars, fully capable of accounting for the observed “freshening and conditioning power,” that is, induction of after-fermentation, of dry hops.
They also noted that the 68.7% figure was for whole cone hops, and that well broken down (powdered) hops resulted in 72-91% their own weight of fermentable sugar being produced in the same time, which may correspond better to pellets used today.