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Can't hit FG

Beerbrewer

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Hi there,

Just brewed a white IPA, and I'm having some trouble hitting my FG.

Measured OG = 1.055, Target FG should = 1.009 but i have 1.022.
Has been in the fermenter for 7 days.

Grain bill:
rice hullls = 2.1%
pale malt = 68%
wheat malt = 12.8%
wheat flaked = 12.8%
victory (biscuit) malt = 4.3%

Mash:
protein rest 50 C = 30 mins
saccharification 64.4 C = 75 mins
mash out 75.6 C = 10 min

Yeast:
Belgian Wit = 2 x dry packet, re-hydrated.

Can anyone give me some pointers on how i can achieve my target FG?



 
Greetings beerbrewer - it sounds to me like your yeast has either fluctuated out (unlikely, but possible), or it has gone dormant, or your readings are wrong. So some questions:

1) what size is your batch?
2) what temperature was your fermentation throughout the fermentation period?
3) how well did you aerate your wort?
4) how long was your lag time before?
 
And to add to KellerBrauer's questions:

Your FG reading is taken with a hydrometer or refractometer?

 
Hi Kellerbrauer and Oginme,

thanks for getting back to me.

batch size into fermenter = 12L
Boil volume = 18L
ferm temp = 20C
wort was aerated very well using air stone
lag time or adaption phase was around 12-15 hours - there was a very thick krausen in the fermenter.
I used a hrdrometer to take the FG but i use a refractometer during mashing, boil & post boil.

I had the same problem with an oatmeal stout i did a few weeks back. OG 1.045, FG 1.022.
I figured it was the large amount of unfermentables and the single infusion mash i did at 68.8C.

This time i changed my mash to allow for protein rest and saccharification hoping it would resolve the issue.

one thing i did not do was mill my wheat flaked or my oats.
Could this be the issue?
 
Let's knock things off one at a time.

I don't mill my flaked grains either and have never had a problem.  I find that in my Corona-style mill the flaked grains become dust really easily and contribute to high trub levels. 

Have you checked the calibration of your hydrometer?  It sounds strange that it stopped at the same FG for two different brews with two different starting gravities.  I would check it against distilled water for a 1.000 gravity reading.

I would recommend also checking your FG with the refractometer.  Using the refractometer tool in BeerSmith, set the calculation for fermenting wort.  You can enter the brix reading from your refractometer and your OG and it will give you a corrected FG based upon that brix reading.  This should correlate with your hydrometer reading if the hydrometer is correct. 

Your lag time sounds normal and unless you had an abnormally low fermentation temperature during the initial stages of fermentation (the first four days or so), I don't know why the yeast would have crashed out early on you.  Having said that, my experience with Belgian yeasts is that they typically need a rise towards the end of fermentation up to around 21C up to 24C to finish off or some strains tend to stall out.  I've only used a couple so my data on this is rather limited, and I have not used that particular strain.

KellerBrauer may have other points and questions on things that I may have missed.

 
Greetings again - the first observation I have, aside from the great points Oginme brings up, is the quantity of yeast used for a 12L (3.2G) batch.  That's a lot of yeast. If you were using a typical 11.5g pack, that's over 4 billion cells.  There could not have been enough oxygen or nutrients to support that much yeast.

Also, if the yeast is a high floculation yeast, it will give you a lower attenuation and if the batch was over pitched, the combination may be the issue and the yeast fell out as a result.

Can you offer a little more information on the yeast you used?

For the heck of it, try agitating the yeast a bit.  If it did stall, agitating it may bring it back.  So, maybe you can follow the suggestions Oginme offered, they may reveal your problem. If not, then shake it up a bit.  Meantime, please post some info on the yeast.
 
Hello again Kellerbrauer and Oginme,

Glad to hear not milling the wheat is not an issue.
Yes have checked the calibration of my hydrometer, all good.
I haven't checked the reading with the refractometer as yet but will do.
Yes it is a lot of yeast. I doubled up on the yeast this time in case it was the issue with the last stout i brewed.
You maybe right in terms of not enough oxygen but the stout i brewed a few weeks ago only used one packet of re-hydrated yeast.
The yeast is mangrove jacks M21 Belgian Wit, high attenuation and low flocculation, http://mangrovejacks.com/products/belgian-wit-m21-yeast-10g

I did a slight agitation by rocking the fermenter and got some reaction.
So i gave it a bit of air using the air stone but i'm worried about oxidation now.
I haven't seen any reaction since recharging the air but will investigate again in the morning.
I have raised the temp to 24C.

 
Greetings beerbrewer,

I'm currently reading the book "Yeast, A Practical Guide to Beer Fermentation" by the founder of White Labs, Chris White.  In the book, Chris states:

"Lack of dissolved oxygen causes many fermentation problems. Stuck fermentations, long fermentation times, underattenuated beers, yeast stress, and off-flavors are often the result of too little oxygen."

The yeast packets contained 10g of yeast each, times 2.  At 18B cells/gram that's 360B cells pitched when only 7g (126B) was needed.  If my calculations are correct, you pitched nearly 200% more yeast than was needed for proper fermentation and as I mentioned earlier, there is no way 12L of wort can contain enough oxygen or nutrients to support that many cells of yeast.

I'm guessing the issue is an exesive amount of yeast was pitched and being there wasn't enough oxygen or nutrients to support that much, they began to die off.  Therefore, I no longer recommend agitating the batch as dead yeast can, and will, cause off flavors in your beer.  My suggestion is to take it on the chin, if you will, and chalk this one up as a learning experience.  Enjoy your brew as it is, learn from it and brew better next time.

Regarding the stout you had problems with, I really can't help or offer suggestions without knowing the particulars.  But I can say, I would not recommend changing your entire brewing method or approach based on the results of one particular batch.  Anything could have caused that batch to spin out.  That doesn't mean every batch will do the same.

Hope this helps!

Good luck!! ;)
 
Hi KellerBrauer,

Thanks for the feedback. Yikes!
I'll drop the fermented wort into a secondary right away.
Do you think i'll have enough viable yeast left for bottle fermentation or would you suggest pitching more yeast after transfering to secondary?

Cheers
Brad
 
Greetings beerbrewer - it's okay, I understood what you meant.

I'm having a hard time answering your question without asking more questions.

1) how long ago did fermentation begin and how long did it last?

If my theory is correct and the yeast did not have ample oxygen and nutrients to survive and fully ferment your wort, than adding additional yeast for bottle conditioning would really be an effort in futility.  Also, if my theory is correct, there MAY not be enough viable yeast to complete the task.  And, at this stage, I would NOT recommend adding additional oxygen as that would surely destroy your brew.  Sooooo.....

Perhaps one of the other brewers has a different opinion, but my suggestion is to rack it to the secondary as you mentioned, then go ahead and bottle it.  If there is enough viable yeast remaining in suspension, it will carbonate.  If not, it won't.

Now the new question is: should priming sugar be added since fermentation was never really completed?  I would say YES.  Go ahead and finish your routine and see what happens.  Worst case, it doesn't work and the batch gets dumped. Best case, you enjoy the batch that caused you to loose sleep :).

I hope this information has helped.  Let us know how it turns out!

Good luck!
 
Hello KellerBrauer,

Thanks for coming back to me again.
Fermentation started on the 8 December around 6pm.
Not sure when it ended as i was away but returned on the 22 December to find it doing nothing.
I'm feel like there is some life in it because when i did agitate it a little as you requested, i did notice some action in the airlock, albeit minor.
Perhaps the last dying breath...
Anyway, i've racked it to the secondary now and will bottle in the next day.
Thanks for all your advice and i'll be sure to let you know how it turned out, unless it kills me...

Cheers!
 
Given that you just started on the 8th of December, I would give it some more time.  Having just racked into secondary, I would suggest giving it another couple of weeks to see if it ferments out with the change.  It is only the 17th of December now, so that is less than 2 weeks in primary.  With a little aeration from your agitation and the transfer, give it some time to see if the fermentation takes off.  With this amount of time in the primary, there is plenty of yeast in suspension to work the gravity down further.

In fact, if KellerBrauer is correct in his assertion of too much yeast leading to stalling (and I think he is on the right track), the existing yeast population will benefit from not having the rest of the yeast cake to compete with for the resources.

One of the other things I have done in the past with one of the two stuck fermentations I have encountered is to add some yeast nutrient to the carboy.  I took a couple of grams in about 50 ml of sterilized water and just poured it in to a Belgian Dark Strong that topped out a 1.032.  Two weeks later it settled at 1.020 and was great.  With so many yeast cells looking for the food and scarce nutrients in the wort, they deplete themselves of sterols when reproducing, leading to weak daughter cells and an inability of the cells to further reproduce.  Adding some nutrients back in will give them a boost in the building blocks they need to strengthen the cell walls and regain some stamina.

 
KellerBrauer said:
Greetings beerbrewer,

I'm currently reading the book "Yeast, A Practical Guide to Beer Fermentation" by the founder of White Labs, Chris White.  In the book, Chris states:

"Lack of dissolved oxygen causes many fermentation problems. Stuck fermentations, long fermentation times, underattenuated beers, yeast stress, and off-flavors are often the result of too little oxygen."

The yeast packets contained 10g of yeast each, times 2.  At 18B cells/gram that's 360B cells pitched when only 7g (126B) was needed.  If my calculations are correct, you pitched nearly 200% more yeast than was needed for proper fermentation and as I mentioned earlier, there is no way 12L of wort can contain enough oxygen or nutrients to support that many cells of yeast.

I'm guessing the issue is an exesive amount of yeast was pitched and being there wasn't enough oxygen or nutrients to support that much, they began to die off.  Therefore, I no longer recommend agitating the batch as dead yeast can, and will, cause off flavors in your beer.  My suggestion is to take it on the chin, if you will, and chalk this one up as a learning experience.  Enjoy your brew as it is, learn from it and brew better next time.

Regarding the stout you had problems with, I really can't help or offer suggestions without knowing the particulars.  But I can say, I would not recommend changing your entire brewing method or approach based on the results of one particular batch.  Anything could have caused that batch to spin out.  That doesn't mean every batch will do the same.

Hope this helps!

Good luck!! ;)

My calcs for a 1.055 wort gravity and 2 10g dry yeast packages. Seems he was under pitched to me.

Cells Available: 200 billion cells
Pitch Rate As-Is: 0.71M cells / mL / ?P
Target Pitch Rate Cells: 212 billion cells
Difference: -12 billion cells
 
Greetings Oginme, Kellerbrauer, Kbar,

Happy new year!

Just wanted to give you an update on what has happened since we last spoke.
I raised the temp to 22C.
I added some yeast nutrient.
I gave the wort some air using my airstone and bike pump (filtered of course).
The ferment started up again, albeit slowly.
I left it for another week and hit 1.010.
While i was worried about oxidation, there wasn't any.
I cold crashed the wort and kegged it.
It has been the most delicious brew to date.

Thanks for all your assistance Oginme and Kellerbrauer!

Best wishes for the new year!

 
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