Insane yeast cell growth; no alcohol production....

[biertourist]

This is definitely NOT the first time that this has happened to me, but the first time I have numbers to back it up....


I made a starter for a "Propagator" pack of 3944 Wit beer yeast (Date: Oct 2009), chilled it down to 70F and pitched it into a 1 Liter starter (nutrients added). I aerated continuously using my sterile air pump and air stone for about 10 hours.

I have INSANE yeast cell growth (1 1/2 inches in a 1/2 gallon growler), but no krausen and no drop in OG...


What would cause yeast to be in "cell growth mode" and not switch over to "alcohol production mode" quickly?

Could an overly large cell (population) growth cause this (Wyeast always recommends no greater than a 10x step-up but I'm WAY, WAY over that)?
Could too much yeast nutrient do this?
Too much oxygen for too long?
-What about leaving on the oxygen for hours, then turning it off, then turning it on?

What about "osmotic shock"? (My starter had way too high of gravity last night (1.080, although I dilluted it with boiled and chilled water back to 1.045 this morning).)

I've had this happen to me in the past when I had a normal gravity starter. I almost always aerate with the aeration stone for a long period of time; is the constant application of oxygen and the myriad of nutrients (this was an all grain starter with yeast nutrient added) to blame?
Do the yeast just see an "opportunity" to grow like mad so they don't bother to convert to alcohol production mode for a while?

Is there anything that I can do to get them to convert to alcohol production mode? (Pitch them into a new non-aerated starter?)



I've never come across this behavior in any literature and I'm at my wits end (we'll, literally at it's beginning)


Adam

[biertourist]

Hmm...

Maybe it's not that they're "not going into alcohol production mode" maybe it's that something that I did is causing them to flocculate WAY, WAY too soon.
(Would adding the water to bring down the gravity cause the yeast to flocculate for some reason?) -Gravity instantly dropped from 1.080 to 1.040.


Adam

[Brandon]

Me thinks you measured your gravity wrong.

[biertourist]

Me thinks you measured your gravity wrong.

Lol! I WISH that was the case.

They're just floculating out of solution without doing ANYTHING. They're little lazy bastard yeasties.

As I haven't gotten any good recommendations on how to motivate them into getting back to work I've resorted to negative reinforcement.

I told them that they better get off their collective yeastie asses and start fermenting that wort, or I'll find other yeasties who WILL do it! "There's a recession on; if you think you can get a better deal somewhere else BE MY GUEST! Jobs fermenting all the sugar and nutrients you can eat, where you only have to produce a little ethanol here and there are FEW AND FAR BETWEEN THESE DAYS!"

Tough love, but I've got a home brewery to run here!

[biertourist]

I think I may have found my answer. I didn't know this was possible but "oxygenation stress" from over oxygenation.

Apparently 10 hours from an oxygen stone during the exponential growth phase was just too much... ; (



http://byo.com/stories/wizard/article/section/121-mr-wizard/931-is-it-possible-to-aerate-your-yeast-too-much

Adam

[alan_marks]

I would also suggest the 12/28/09 podcast of BrewStrong on wort aeration. They cover quite a bit on some of the myths of proper aeration techniques.

Hope this helps,
Alan

[a10t2]

If you're using air, then no, you don't have to worry about over-oxygenating. I have to agree with Brandon: your gravity measurements probably aren't correct. Whether in "cell growth mode" or "alcohol production mode", the yeast need energy to function. You're obviously growing a large amount of yeast, so they must be consuming sugars.

[Nyakavt]

If you're using air, then no, you don't have to worry about over-oxygenating. I have to agree with Brandon: your gravity measurements probably aren't correct. Whether in "cell growth mode" or "alcohol production mode", the yeast need energy to function. You're obviously growing a large amount of yeast, so they must be consuming sugars.

Agreed. Even if the yeast produce no ethanol, the gravity reading will still decline if more yeast is produced since they must consume the sugar to do so.