Fermentation restarted after dry hopping?

Some great replies to the op from all you guys and its very much appreciated. I probably dry hop 1 in 3 of my brews, usually the ales but have never had this happen before and seeing as it has happened only to one of two identical brews, apart from the hop type, it was a little worrying. After reading through the thread and following up what you guys have said by researching it online the general feeling I guess is that it is indeed CO2 being released or knocked out of suspension. Having said that and having scoured through my brew books and online sites I'm surprised at how little information there is out there regarding this one aspect of dry hopping and the causes or likelihood of it happening (and the possible effects on the end product) with particular types of hops, if indeed it is hop type related for example.

Both my brews were hopped in primary, (I usually only do a secondary with big beers over 7%) and both were dry hopped with 100g pellets. That might sound a lot but it has to do with the reason for me doing two identical brews side by side, hop research and the different results from doing single hop beers. Its been interesting and I'm thinking two very similar grain bills can produce two very different beers under the same conditions but with one simple difference, the hops, which is what I was attempting to learn.

Cracking forum this, much appreciated guys. Next up, a Maple Wheat beer so I might be plucking your brains again :)

terrym said:

You are very unlikely to restart a fermentation after a dry hop especially if the yeast has done its job and no extra fermentable sugars are added.

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Although the science states otherwise. The yeast has fermented all available sugars before dry hopping, then the introduction of hop based diastase enzymes further breakdown maltodextrines in the wort to create more sugars for the yeast to ferment.

The likelihood is that a number of factors mentioned come into play.

Sadfield said:

Although the science states otherwise. The yeast has fermented all available sugars before dry hopping, then the introduction of hop based diastase enzymes further breakdown maltodextrines in the wort to create more sugars for the yeast to ferment.

The likelihood is that a number of factors mentioned come into play.

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Whenever I have dry hopped at the end of the primary the SG reading remains the same or at best may only drop a point, so my empirical data does not support your statement, but that's only my experience.
However I'm always open to new ideas. :thumb:
So lets see some factual scientific evidence please, including data on the likely extent of how much more fermentation we are likely to see and under what conditions which prevail in a home brew FV as the result of the addition of a dry hop?

terrym said:

Whenever I have dry hopped at the end of the primary the SG reading remains the same or at best may only drop a point, so my empirical data does not support your statement, but that's only my experience.

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Surely, a point drop is evidence of further fermentation?

However I'm always open to new ideas. :thumb:
So lets see some factual scientific evidence please, including data on the likely extent of how much more fermentation we are likely to see and under what conditions which prevail in a home brew FV as the result of the addition of a dry hop?

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I think there is plenty of evidence in the link I posted previously.

Reference to it in this document from 1916, on page 336.

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1916.tb02377.x/abstract



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I'm pretty sure it's due to nucleation sites in the hop particles causing CO2 to come out of solution, just like putting sugar in a glass of Coke causes it to foam up.

strange-steve said:

I'm pretty sure it's due to nucleation sites in the hop particles causing CO2 to come out of solution, just like putting sugar in a glass of Coke causes it to foam up.

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This is the likliest reason isn't it?

Do American hops come with seeds? I haven't noticed, I know English ones do but European farmers grow their hops without any male hops present, so European hops - Hallertau, Saaz etc, come sans seeds.

Hops do have antibacterial properties but that doesn't affect yeasts (you can see why there might be a problem for beer if it did). I can imagine a scenario where hops might have wild yeast or mould in them, which would then get into the beer. I've never had it happen.

I did a bulldog double IPA kit in the summer which fermented from 1062 to 1012/14 and I was of the opinion it was well and truly finished before I dry hopped it, with the summit and simcoe pellets supplied with the kit. After a few days it was well and truly going again though and fermented out all the way to 1000/02. Dry as a nuns crotch it is, and massively potent, I've got a couple of dozen bottles left which I will drink but it's not been a pleasant brew really being too strong and dry. I've dry hopped a few since and not experienced the same again though.

Poochops said:

I did a bulldog double IPA kit in the summer which fermented from 1062 to 1012/14 and I was of the opinion it was well and truly finished before I dry hopped it, with the summit and simcoe pellets supplied with the kit. After a few days it was well and truly going again though and fermented out all the way to 1000/02. Dry as a nuns crotch it is, and massively potent, I've got a couple of dozen bottles left which I will drink but it's not been a pleasant brew really being too strong and dry. I've dry hopped a few since and not experienced the same again though.

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That definitely sounds like an infection of some sort.

Nucleation of Co2 may be one initial factor, but residual co2 in beer at room temp is quite low, a 5th of that of Cola which goes flat very quickly, so may not explain a persistent degassing.



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Not an unknown phenomenon btw :

http://www.homebrewtalk.com/showthread.php?t=443164


http://forum.northernbrewer.com/t/dry-hopping-cause-airlock-bubbles/21155

Interestingly the 2nd one was also citra

I've just taken gravity readings from both batches and they are both stable at 1.010, the same reading I got before I dry hopped them. I smelt and tasted both samples just to see if I could detect any signs of infection rather than to compare taste and have to say that both seem very healthy with fine aroma and very clean tasting. I'm considering kegging the EKG as its sitting nice and quiet but as long as the Citra is still producing airlock activity I will leave it be.

ravey said:

Not an unknown phenomenon btw :

http://www.homebrewtalk.com/showthread.php?t=443164


http://forum.northernbrewer.com/t/dry-hopping-cause-airlock-bubbles/21155

Interestingly the 2nd one was also citra

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It is interesting yeah, I wonder if anyone who has experienced this behaviour has noted what hop varieties its happened with?

Sadfield said:

Surely, a point drop is evidence of further fermentation?

I think there is plenty of evidence in the link I posted previously.
Reference to it in this document from 1916, on page 336.
http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1916.tb02377.x/abstract

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Sadfield
I owe you a reply regarding your comment that 'hop based diastase enzymes further breakdown maltodextrines' and so fermentation restarts following dry hopping.

I have had a look through the paper you referenced. I cannot agree that it contains 'plenty of evidence' that this happens, I see no facts, just many rambling ideas. However this may have been the style of the day, being 100 years ago, and further it looks to have been the basis of a presentation so space for detail would possibly have been limited. To quote the saying, the 'devil is in the detail', and back up to the discussion may be research documents not seen here, perhaps long since buried.

So as far as I am concerned it might be a phenomenon that occurs but I cannot really accept that it would be responsible for a significant re-ignition of the fermentation, more perhaps a very slight 'freshening' as the paper author mentions.

Putting this into a dry hop context for the home brewer I am still of the opinion that the single reason for apparent bubbling after a dry hop is nucleation. I have my own first hand experience of this, one to two hours after a dry hop, bubbles rising, six hours or so later nothing.

Finally the one point drop I have experienced on occasion following a dry hop is, as far as I am concerned, down to incomplete primary given the way I do things. In other words the longer I leave a primary before I dry hop, the less likely further falls in SG readings become.

Given the above I think it will be best now if we agree to differ on this, and let others on here decide for themselves on this issue, using the information they have been provided.

strange-steve said:

That definitely sounds like an infection of some sort.

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You would think so, it passed my mind too. I just opened a bottle to drink watching Planet Earth II, and it certainly tastes OK. In fact it's mellowed a bit with age having had three months in the bottle, it doesn't appear to be infected but I don't have any experience of how an infection affects a brew so it's difficult to say. It's certainly not offensive in any way so I'd err on the side of it not being infected given how long it's been in the bottle now. What do you think?

Guys this thing is still bubbling away and I don't like the idea of leaving the dry hopping for much more than a week. Do you think it is worth putting into a secondary, maybe that will reduce whatever affect is causing the activity?

Amidared said:

Guys this thing is still bubbling away and I don't like the idea of leaving the dry hopping for much more than a week. Do you think it is worth putting into a secondary, maybe that will reduce whatever affect is causing the activity?

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Is the FG actually changing? If not, I wouldn't worry about it and bottle/keg.

After 3-4 days its unlikely to be co2 coming out of solution, so providing there is no other indicators that you may have an infection, I'd crash cool and package, as DoctorMick recommends. If kegging you have the option to vent any extra co2, although if bottling I would prime on the low end for the style.

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DoctorMick said:

Is the FG actually changing? If not, I wouldn't worry about it and bottle/keg.

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No its still at 1.010, not reducing at all. If its co2 and I bottle, will the co2 be re absorbed into brew? If so then I think you're right and there's nothing to gain by waiting, may as well keg it.

Good to read this - just dry hopped my New World Saison kit - FG 1.008, has been for 4-5 days no airlock activity, 10 mins later bubbles through the airlock, will leave it the required time then bottle, not expecting any change in FG. Cheers

normally do BIAB and dont dry hop so this was a first for Dry Hopping and a kit :-)

This happened to me just this week
- I stuck on a Coopers Cerveza with BE1.
- Left it one week
- Fermentation had stopped / gravity stable
- Added 30g Citra
- Fermenter has been doming for the last 3 days - not a lot of CO2, but enough to make me wonder

Will be bottling tomorrow, after 2 weeks primary. I guess time will tell!

Cheers

martin