What went wrong with my fermentation, was it the mash?

[BrauTim]

I was feeling pretty good about last weeks brewday, collected 44 litres @1.051 of an english ale. Into the fermenter with 2 x 12g packs of dried yeast which I had rehydrated.

The fermentation was going well for 48 hours, then it stopped, completely @ 1.020 (I was aiming for 1.010), flavour seemed good though!

OK, give it a stir, not much action, add half a packet of yeast (rehydrated), still not much action, waited 24 hours and added 500g of Dextrose solution, BOOM, within 30 mins we're off again, so I made up another 500g solution in the hope I can get a bit more alcohol into this beer, those yeasties were hungry, so I can only conclude that all the fermentable sugar had been consumed in the first 48 hours.

I've not had a stuck ferment before, so this is new to me.

I have been thinking about what has caused this, could it be the mash, I mashed at 68 C for 90 mins, I didn't test for conversion and just assumed it had converted, I also didn't think 68 C would not get all the fermentables out. pH was good at 5.3 and I got around 80% efficiency.

The sugar added around 5 additional gravity points, so other than more alcohol, does anyone know what effect this might have on the beer, can I expect to drop below 1.020 ?

Anyone had something similar?

[dinnerstick]

i would look at fermentation rather than mash, in my experience a few degrees difference in the saccrification temp does not alter the fermentability to a great degree (ie not a 5 gravity point swing), and at 68 you have optimal alpha activity as well as some beta, it's going to convert quickly! i do lots of 'single infusion' type mashes at 68 (60 minutes) and get highly fermentable wort, which a good pitch of any self-respecting yeast can take down to the 1.010 range.
i have a few questions then, when you added dextrine (what was the dextrine, was it malto-dextrine? or pure glucose? the former is not hugely fermentable by brewer's yeast) how did you monitor the fermentation, did it give off gas or really change gravity?
what was the yeast, how old were the packs, could the temp have dropped, i'd look more toward these variables myself. did you oxygenate well, although dry yeast shouldn't need a lot of oxygen...
or, was this a wacky experiment with 30% crystal malt?? (<- not a highly serious question)
good luck!

[BrauTim]

i would look at fermentation rather than mash, in my experience a few degrees difference in the saccrification temp does not alter the fermentability to a great degree (ie not a 5 gravity point swing), and at 68 you have optimal alpha activity as well as some beta, it's going to convert quickly! i do lots of 'single infusion' type mashes at 68 (60 minutes) and get highly fermentable wort, which a good pitch of any self-respecting yeast can take down to the 1.010 range.
i have a few questions then, when you added dextrine (what was the dextrine, was it malto-dextrine? or pure glucose? the former is not hugely fermentable by brewer's yeast) how did you monitor the fermentation, did it give off gas or really change gravity?
what was the yeast, how old were the packs, could the temp have dropped, i'd look more toward these variables myself. did you oxygenate well, although dry yeast shouldn't need a lot of oxygen...
or, was this a wacky experiment with 30% crystal malt?? (<- not a highly serious question)
good luck!

Sorry I meant to write dextrose not dextrine, I've corrected in the original.

I thought the same about the mash temp also, this should not be a problem. I ferment in a temp controlled fridge which was at a steady 19 C and I increased the temp by a couple of degrees once I noticed it was stuck, so I've ruled that out, I only added the sugar yesterday so not had a chance to check gravity, but a quick look at the airlock shows it bubbling at a steady 1 per second rate and has been now for over 15 hours and it restarted very quickly once I added sugar, so fermenting normally again.

It could be the yeast that is a problem, however when I added some more of the same yeast nothing happened and given that it fermented 30 points in 48 hours, that is quite normal. It was only when I added the sugar that it started fermenting again (also had some fresh yeast in there from the earlier attempt to get it going). The yeast is NBS Ale yeast 2, which I believe is repackaged Mauri ale 514, no date on the package. I aerated well as always by shaking the hell out of the wort.

Everything points to it being a lack of fermentable sugar, there is a possibility that it could be that the temp probe on the BM is reading too low, I'll have to test that and I'm not going to rule out yeast........yet

There is about 10% crystal in the brew but that was added at 60 mins along with some black malt, so I can't see that having an effect.

EDIT: the beer has dropped to 1.018 today and fermentation is slowing, I think it will reach around 1.016 if I'm lucky, I'll get a 5% beer and I'll be happy with that, I didn't want a dry beer anyway :/

[ChilliMayne]

The only comment I have is why bother rehydrating a dried yeast sachet? There really shouldn't be any point.

[Dicko]

I would tend to lean the blame on the dried yeast.
The viability of a pack is only as good as the way it has been stored throughout its life and its age.
I tend to make a starter for dried yeasts these days and I know that many say it is not necessary but In my experience I have had much better results.
The effort is minimal compared to the time and money you put into a brew and not have it come out as expected.

[Dicko]

I just did a search on that yeast....link below, and I note that the manufacturer does not provide accurate attenuation figures.

http://www.maurivinyeast.com/upload/MAURIBREW%20ALE%20TDS.pdf

I read a topic on this yeast on another forum and a brewer did a side by side test with this yeast with US 05 and with the same wort the US05 got to FG 1010 and the 514 only got down to FG 1014.

While this info is not conclusive it may offer some light on your problem.

[BrauTim]

I just did a search on that yeast....link below, and I note that the manufacturer does not provide accurate attenuation figures.

http://www.maurivinyeast.com/upload/MAURIBREW%20ALE%20TDS.pdf

I read a topic on this yeast on another forum and a brewer did a side by side test with this yeast with US 05 and with the same wort the US05 got to FG 1010 and the 514 only got down to FG 1014.

While this info is not conclusive it may offer some light on your problem.

The attenuation they give is from 1.040-1.045 to 1.008 this would give an attenuation around 80%, not the 65% I was getting.

50-80g/hl gives 0.5g per litre at the low end, for 44 litres I needed 22g, I pitched 24g and with the wort over 1.050 I might have needed 3 or 4 packets of yeast, so maybe I underpitched!

But what is still puzzling is that when I did pitch an extra 1/2 packet, nothing happened! 24 hours later when I added the dextrose it all started again.......still wondering :/

[swiggingpig]

But what is still puzzling is that when I did pitch an extra 1/2 packet, nothing happened! 24 hours later when I added the dextrose it all started again.......still wondering :/

I wouldn't have thought there was much oxygen left for the the new pitch of yeast and maybe that delayed it starting fermentation

[niels]

But what is still puzzling is that when I did pitch an extra 1/2 packet, nothing happened! 24 hours later when I added the dextrose it all started again.......still wondering :/

Did you pitch the extra dried yeast directly into your beer or did you rehydrate it first? When you pitch dried yeast directly in beer it comes into a very harsh environment (about half of the cells die), so you need the new yeast to adapt to this new environment: rehydrate it and make a little "starter". This way the yeast is in full action and used to a environment containing alcohol when you pitch. You can even go a bit further and scale up the "starter" using beer from the fermentor...

When you added dextrose you added very simple sugars. It is normal that fermentation starts again as these weakened yeast cells get a bunch of easy candy to eat. Instead of trying to chew on the more complex sugars left in the wort/beer the yeast turns it attention to these simple sugars.

Niels

[BrauTim]

But what is still puzzling is that when I did pitch an extra 1/2 packet, nothing happened! 24 hours later when I added the dextrose it all started again.......still wondering :/

Did you pitch the extra dried yeast directly into your beer or did you rehydrate it first? When you pitch dried yeast directly in beer it comes into a very harsh environment (about half of the cells die), so you need the new yeast to adapt to this new environment: rehydrate it and make a little "starter". This way the yeast is in full action and used to a environment containing alcohol when you pitch. You can even go a bit further and scale up the "starter" using beer from the fermentor...

Yes, I rehydrated.

When you added dextrose you added very simple sugars. It is normal that fermentation starts again as these weakened yeast cells get a bunch of easy candy to eat. Instead of trying to chew on the more complex sugars left in the wort/beer the yeast turns it attention to these simple sugars.

Niels

Sounds plausible

Looks like it has reached 1.016 as final now, I don't think it tastes too sweet but it's early days.

[cpa4ny]

I personally didn't have a stuck fermentation situation that another rehydrated pack of Notty couldn't fix.

I also think that injecting pure O2 into the chilled wort prior to pitching yeast really improved the fermentation & consequently the beer. Highly recommend it.

[ChilliMayne]

Given your data BrauTim, the attenuation of your yeast is almost 61%. Ideally we would all like a range of 70-80%. But from 65% and higher is not bad either. but it all depends on what the strain of yeast you used was and what performance it promised?