Losing flavour in primary fermentor following small heat rise

[DominicRL]

Hi folks - a question following my two most recent brews where I seem to have lost a lot of flavour and aroma in the last few days of fermentation with small temperature rises.

The first was a NEIPA and the second a Belgian Blonde, it’s been very cold so I’ve been relying (for my plastic fermenters) on heat pads, in both cases the temperature has increased by a few degrees (19-23 & 18-20) in the final few days (a diac rest for the former, natural temperature increase for the latter but both within healthy ranges for the yeast). I make a habit of trying small amounts when taking gravity readings and after active fermentation (gravity within 5ish points of FG), I recorded really positive stone fruit and banana flavors respectively in the beers which I’d aimed for, the aroma in both cases was fantastic. However after the temperature rise and before bottling, this flavour seems to have largely disappeared in favour of something much more straightforward (not unpleasant but not the desired effect either!) I’m worried the extra heat has killed the gentler flavors which developed, but this kind of rise is regularly recommended by brewers so I’m a bit baffled as to best practice.

Is this something you folks have experienced, very grateful for any advice/thoughts!

Thanks,
D

 

[Caramel Ox]

I will frequently sample daily and yes I have recorded similar observations about diminished flavours for some brews. You may find it comes back once the bottles are ready for drinking. You don’t really have any choice - you can’t lock in the taste at a particular time it has to go to completion. You can hold at a steady temperature for ales with no D rest, it will just take longer to complete - I think it’s the completion not the small temperature change that causes the difference in taste.

 

[MashBag]

The warmer the fermentation the more it will blow off more delecate flavours to the neighbours. You will also find the yeast cleans up during the process.... Perhaps they didn't like those flavours as much as you did

 

[DominicRL]

I will frequently sample daily and yes I have recorded similar observations about diminished flavours for some brews. You may find it comes back once the bottles are ready for drinking. You don’t really have any choice - you can’t lock in the taste at a particular time it has to go to completion. You can hold at a steady temperature for ales with no D rest, it will just take longer to complete - I think it’s the completion not the small temperature change that causes the difference in taste.

Glad I’m not alone here, it really seems to happen at those final few gravity points so I think I may try a split batch next time - one where I drop the temperature immediately as I hit FG and another with a diac rest to see the difference. Fingers crossed it does come back in the bottle as you say!

 

[DominicRL]

The warmer the fermentation the more it will blow off more delecate flavours to the neighbours. You will also find the yeast cleans up during the process.... Perhaps they didn't like those flavours as much as you did

That’s good to know, I may try repeating at a cooler temperature to see if I can keep the more delicate flavours - the annoying thing is that the yeast in both cases was meant to impart what I mentioned (and did for a couple of days) but it seemed to disappear those few gravity points before FG, given the cold weather (and my Inkbird struggling to hold the temp, it floated between 16-20 rather than a solid 20), I’m wondering if the up/down nature has also been a major issue, but won’t be able to test that until I splash out on some more expensive gear!

 

[dlowe1992]

Not sure it really helps, but here goes anyway.. I like you taste at every sample point. I've noticed with a couple of beers (hope forward blonde particularly) that the flavour wasn't as hoppy and fresh after racking to keg / bottle and carbonating / priming and been really disappointed. However, I then noticed a better flavour after a couple of weeks. This would seem to fly in the face of the theory that hoppy beers are best drunk fresh. Only thing I can put it down to is the bitterness mellowing out allowing the hop flavours to shine through more. Either way, I say judge it after it's had a suitable conditioning time. As I never brew NEIPA's, I've no idea what that it is, but I'd say your blonde wants a couple of weeks conditioning before you make your mind up.

As I say, may be no help at all, but all is certainly not lost

 

[hoppyscotty]

Think alot of it depends on the yeast and the contribution you expect from the yeast. I don't taste during fermentation...but my thinking and approach has always been the flavour contribution from the yeast depends on fermentation temperature and the hops depends on 'locking the hop oils in the beer' since they are volotile compounds and like to escape into the fermenter headspace and through the airlock. For this reason I tend to dry hop cool - at 15 degrees or so and might even try dry hopping at cold crash temps as I've read recently this also works...so for me getting hop flavour in the beer is all about retention of the volatile compounds.

Its hard to really know what affects what without doing back to back batches.

The biggest loss of hop flavour once you've legged is the loss of aroma into the increasing head space of the keg...I find the beer looses hop aroma and flavour the deeper you get into a keg and the CO2 in the keg takes on all that lost aroma...I would love to serve from a keykeg style keg, but since they're disposable and not reusable that really isn't a viable option.

 

[DominicRL]

Not sure it really helps, but here goes anyway.. I like you taste at every sample point. I've noticed with a couple of beers (hope forward blonde particularly) that the flavour wasn't as hoppy and fresh after racking to keg / bottle and carbonating / priming and been really disappointed. However, I then noticed a better flavour after a couple of weeks. This would seem to fly in the face of the theory that hoppy beers are best drunk fresh. Only thing I can put it down to is the bitterness mellowing out allowing the hop flavours to shine through more. Either way, I say judge it after it's had a suitable conditioning time. As I never brew NEIPA's, I've no idea what that it is, but I'd say your blonde wants a couple of weeks conditioning before you make your mind up.

As I say, may be no help at all, but all is certainly not lost

Now this does give me some hope, the yeast profile suggests I should be getting banana / stone fruits in those beers so it makes sense that maybe something needs to mellow to let those flavours shine (banana is a gentler flavour than standard hop bitterness so would make a lot of sense). I’ll do as you suggest! NEIPA is just New England IPA, aka ‘hazy’s’, I’m quite new to the style. D

 

[DominicRL]

Think alot of it depends on the yeast and the contribution you expect from the yeast. I don't taste during fermentation...but my thinking and approach has always been the flavour contribution from the yeast depends on fermentation temperature and the hops depends on 'locking the hop oils in the beer' since they are volotile compounds and like to escape into the fermenter headspace and through the airlock. For this reason I tend to dry hop cool - at 15 degrees or so and might even try dry hopping at cold crash temps as I've read recently this also works...so for me getting hop flavour in the beer is all about retention of the volatile compounds.

Its hard to really know what affects what without doing back to back batches.

The biggest loss of hop flavour once you've legged is the loss of aroma into the increasing head space of the keg...I find the beer looses hop aroma and flavour the deeper you get into a keg and the CO2 in the keg takes on all that lost aroma...I would love to serve from a keykeg style keg, but since they're disposable and not reusable that really isn't a viable option.

Thanks Scotty. I think that makes a lot of sense re yeast flavours being largely about temperature, for the Belgian the banana was meant to come from the T58. My thinking is either the fluctuation due to cold weather (poor heat pad can only do so much) has done this, or as others have suggested the flavour will return during conditioning. For the NEIPA I’m less sure, I’m rarely convinced in increasing temperatures at the end, I think the 3c hike may have done more harm than good.

Completely agree with you on the dry hop side, I’d rather risk hop creep (especially as it dissipates) than little hop flavor so tend to dry hop a little cooler than I had in primary, especially where there is a base heating element otherwise I find there’s a real risk of soap flavours (sapponification I believe it’s called).

Yet to get into kegging, that is the next mission!