Author Topic: Loss of yeast activity  (Read 6511 times)

deerelk4x4

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Loss of yeast activity
« on: February 10, 2009, 11:06:59 PM »
I have recently tried brewing a pumpkin beer.  I boled my wort, added the pumkin, pitched my yeast starter (which was showing good signs of good activity) and set my fermentor in next to my others.  After two days i still haad no sign of yest activity in the beer.  Pitched a new batch of yeast, and again no yeast activity.  OG was 1.045 when pitching yeast for the second time.  What is my problem?

Offline MaltLicker

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Re: Loss of yeast activity
« Reply #1 on: February 11, 2009, 06:09:34 AM »
.....set my fermentor in next to my others.  After two days i still haad no sign of yest activity in the beer.  Pitched a new batch of yeast, and again no yeast activity.  OG was 1.045 when pitching yeast for the second time.

What is total volume of wort?
Original OG when you first pitched? 
How do you aerate the wort so the yeast can grow/multiply before eating? 
Yeast strain, amount pitched and pitching temperature?
Extract, all-grain, use of yeast nutrients?

With the high SG after two days, and the 2nd attempt, you can rule out a loose airlock or lid.  But was there any movement from 1.0XX down to 1.045?  Were these White Lab tubes or dry yeast packs?  With Wyeast packs you can verify viability when the package bloats.  Mis-handling or extreme age could've killed or vastly reduced your yeast in the packages. 

Gravity seems low enough that enough healthy yeast should do OK.   Some yeast are known slow-starters, and if the aeration was poor, and the temperature too cold, and the wort was 11 gallons of 1.070, and the extract was old, and there were not enough yeast nutrients in the wort, and you pitched one tube of low-viability yeast, any combination of any of these factors could make for a poor fermentation or a near no-go. 

You could try a reliable strong-fermenting yeast like Wyeast 1056 w/o a starter if the volume is under 5.5 gallons.
« Last Edit: February 11, 2009, 06:12:53 AM by MaltLicker »

deerelk4x4

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Re: Loss of yeast activity
« Reply #2 on: February 11, 2009, 09:57:17 PM »
What is total volume of wort?

1.5 gal (small sample batch to check flavor and ingredient requirements for the pumpkin

Original OG when you first pitched?

1.045 OG

How do you aerate the wort so the yeast can grow/multiply before eating?

aerated by shaking my wort once cool and in the fermentor. (I use this method with all my beers and have had no problems)

Yeast strain, amount pitched and pitching temperature?

First pitch of yeast was a starter using Muntons yeast.  Second was a starter using Doric.  Temperature at first pitch was 70 degrees, second pitch was 64 degrees.  I have used both of these before in similar conditions with no problems.  My yeast starter was approximately 1 pint water with .25 lbs light DME.  Each starter should good viability over the two day period i set them in motion.

Extract, all-grain, use of yeast nutrients?


All-grain- grains bought from my HBS same day.
No yeast nutrient used (never used yeast nutrient before)

This was my first attemp using fruit and I am wondering if i should have used yeast nutrient.  My only other question is if I make a third batch of starter with yeast nutrient, will it be able to convert the unused sugars currently available or should i toss what I currently have and try again with a new fresh batch.

any pointers?

BTW

I still have the fermentor sitting in about 65 degrees and air locked ready to try anything else before throwing it out.


Offline MaltLicker

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Re: Loss of yeast activity
« Reply #3 on: February 12, 2009, 06:33:12 AM »
If the starters grew and looked healthy, they should have ripped thru that little wort in hours.  Could it have finished overnight so you missed all activity, or the airlock leaked, and it is the hydro that is faulty?  Seems like there would have been a krausen and a crud ring, though. 

I just checked Mr. Malty's yeast calculator, and for 1.5 gal of 1.045 it said just 20% of one 11g dry yeast was sufficient, so clearly WAY more yeast than necessary was used.  I don't know if such severe over-pitching can completely stall out and do absolutely nothing, i.e., not change the gravity at all. 

Could it be possible that it chewed thru the sugars so quickly that it had no time to create a krausen or ring? 

Just to be sure, Can you check your hydrometer to verify it's not broken?  And taste the wort/beer to verify it's still sweet?  At 1.045 it is a near-perfect sugar solution (1# sugar per 1 gallon water of 1.046.) 

If it is not already beer, I can't imagine what would stop two active starters from doing that small job. 

If it tastes sweet, and still clean (not souring, etc.) then maybe try a third dry or wet yeast with no starter.  Half of a 5g package or one-third of a 11g package will suffice. 

I've read that it is not necessary (even bad) to do a starter with dry yeast.  The mfr prepares the yeast for storage, building up the glycogen and sterols in the yeast, so that all the yeast needs prior to pitching is proper H2O re-hydration.  Dry yeast makers say making starter actually weakens the yeast by depleting those built-in energy reserves.  Even so, you should have had plenty of yeast to process 1.5 gals of 1.045 (twice).  But in the future, you can simply follow the mfr guidelines for re-hydrating 30 minutes before pitch time and avoid the pre-planning and work of a starter if you wish. 

As I circled back thru this twisted and lengthy reply, I recall that I once had a problem with my starter gravities being too high, and I was essentially drowning my wet yeast in a high-sugar-then-alcohol bath, likely stunting them rather than boosting them.  If the wort was severely over-pitched, then the starter was insanely over-pitched. 

Is it possible that the yeast competed so fiercely for the limited food in the starter that they wiped themselves out?  Depleted those reserves, starved, mutated and lost ability to process wort sugars?

Edit:  found this Wyeast link on the effect of yeast pitch rates:   http://www.wyeastlab.com/com-pitch-rates.cfm
« Last Edit: February 13, 2009, 07:10:28 AM by MaltLicker »

deerelk4x4

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Re: Loss of yeast activity
« Reply #4 on: February 12, 2009, 06:06:47 PM »
Thanks for the responses.  I will check my gravity and hydrometer (although it was new when used) and if necessary try another batch of yeast. I am most concerned of the off flavors that the dead yeast can give off, if in fact they  worked so hard and fast that they were finished before really getting started.

I too would have expected a crausen ring, but none exists currently, which is the cause for my concern.

I will post back with my results.

Thanks all.

deerelk4x4

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Re: Loss of yeast activity
« Reply #5 on: March 12, 2009, 10:24:03 PM »
checked the gravity, it was still at 1.045, and had taken on a foul cat box aroma.  Dumped it out before it started to provide a visible evidence of a science experiment gone bad.  Any ideas as to what may have gone wrong?


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Re: Loss of yeast activity
« Reply #6 on: March 13, 2009, 07:22:29 AM »
Is it possible that the yeast competed so fiercely for the limited food in the starter that they wiped themselves out?  Depleted those reserves, starved, mutated and lost ability to process wort sugars?

The above idea still seems a long-shot, but something kept the yeast from getting started, allowing the catbox bacteria to take over.   I highly recommend using the yeast calculator at www.mrmalty.com to determine the specific yeast needs for each batch:  it always depends on wort volume, gravity, style, and your desired yeast/ferm character.  I was making starters all the time, but my 4 gallon batches don't typically need one if the package is fresh and I want some ferm character.  Also, I learned recently that you can make a 1L or 2L starter to ensure yeast health, and just pitch the amount needed into the wort.  Toss the rest, or use it to bump up more yeast for a subsequent bigger batch.