Urgent! Help me save my underpitched Marzen :)

[Keiron]

I brewed a Marzen today and realised I did not have enough yeast and the stores are closed.

OG 1.055

Rehydratet 50 grams W-34/70 and pitched in 17 gallons at 55 degrees fahrenheit. The yeast is from april 2014, so a viability of about 70% according to mr.malty leaving me with a pitch rate around 800 000 x ml x plato, so almost an ale-pitch.

The stores does not open until 36 hours from now.

Should I:

A: Leave it be and ferment as planned.

B: buy yeast when stores open and Re-oxigenate and pitch then? Will the new yeast use all the added oxygen and avoid oxygenation of the beer?

C: re-pitch some WLP810 from a brew I cold-crashed 5 days ago, combining this yeast with the already pitched W-34?

 

[drunkEnough4U]

You could pitch what you have, then buy more yeast and pitch it into the fermenting wort as a sort of staggered yeast addition. I doubt it would change the beer much at all unless it's a super strong beer, in which case it'll just help ferment better.

 

[Keiron]

What worries me is what will happed during the lag phase and what consequences this will have for the beer later. I am leaning towards mixing yeasts just to avoid underpitching.

 

[drunkEnough4U]

Hmmmm, I'm in no way super knowlegable so if I'm wrong please somebody correct me but I think if you under pitch the yeast will just go dorment or die and then nothing happens until you repitch.

 

[okiedog]

Buy more yeast when the store opens and add to your fermenter. You can add some yeast nutrient at the same time., if haven't already added it. You should not have to re-oxygenate if it was already oxygenated sufficiently to.

I've had to add more yeast to a batch or two. They started fermenting within a 6 - 12 hours after the 2nd addition, and turned out just fine. Of course it's best to pitch sufficient yeast to begin with, but letting a batch go with insufficient yeast cell count can lead to a number of problems: under attenuation, off flavors, metallic tastes etc.

 

[brew_ny]

I would pitch some of the WLP810 instead of waiting

all the best

S_M

 

[Keiron]

Thank you for the suggestions guys!

I do believe I would have to add more oxygen if I pitched more yeast after 36 hours, as this yeast also would need oxygen for sterol production, and the wort would be depleted from oxygen by then. But if it is safe to add oxygen that late if you pitch more yeast I would really like to know? Also, would the already pitched yeast be negatively affected by the underpitch?

However, not knowing the answers to the uncertainties above, I ended up with adding more yeast from a different strain, but not the WLP810 I became unsure of the health of the WLP810 as it had not been properly cooled and had become brownish. Therefore I added
....Safale US-05 (which I also had available)! My reasoning behind this was that I would rather have a well tasting, but maybe not a 'true' Marzen, than a beer with off-flavours due to severe under-pitching. My guess is that US-05 being such a neutral and crisp yeast it probably will not dominate the beer as it will be working in its absolutely low-end of the temperature spectrum, while the W-34/70 will be more comfortable. Also, it was a smaller pitch (40g vs 50g, same viability), 4 hours later.

So, did I f**k up?

 

[IslandLizard]

The part I don't get is why even trust Mr. Malty for dry yeast viability calculations? Dry yeast is very stable, and lasts the longest when kept frozen, for several years even past its "expiration" date. If you properly re-hydrated the yeast there should have been enough cells for a 17 gallon lager pitch.

I doubt the US-05 even wakes up at 55F.

 

[Keiron]

The part I don't get is why even trust Mr. Malty for dry yeast viability calculations? Dry yeast is very stable, and lasts the longest when kept frozen, for several years even past its "expiration" date. If you properly re-hydrated the yeast there should have been enough cells for a 17 gallon lager pitch.

I doubt the US-05 even wakes up at 55F.

According to these experiments, Mr. Malty's viability calculations seems quite accurate.

So assuming Fermentis yeast ships with about 20 billion cells per gram, even though they state 6 billion cells per gram (probably worst case estimate) it will be underpitched. A 17 gallon 1.055 gravity lager pitch would require 1.500 000 cells * 64352 ml * 13.5 plato = 1303.13 billion cells.

50 grams of 100% viable yeast equals (assuming 20 billion cells pr gram) 1000 billion. Since the yeast obviously is not 100% viable, let's assume the viability calculations of Mr. malty still is wrong and the yeast is for example 90% viable I am still 400 billion cells short.

US-05 has a working range of 53 to 77 degrees fahrenheit.

EDIT: found this quote from a FAQ on Fermentis homepage: "The sachets are stable for two years from date of manufacture with no significant loss of viability and fermentation activity" so assuming the tests conducted on dry-yeast viability at seanterrill.com was incorrect, maybe due to the use of methyle blue, the yeast actually could have a viability of 90% or above. However, it's still about 400 billion cells short. But I'm starting to doubt if it was still worth it pitching the US-05...Maybe you are right IslandLizard

EDIT2: From the sticky regarding dry-yeast, as well as in this thread it is stated that an Fermentis packet contains in average 150 billion cells. This equals 13 billion per gram and seems more reasonable from several different sources, including the Brewers Friend yeast calc and this BYO article.

Assuming 90% viable cells the pitch rate suddenly looks like this:

(50*13)*0,9 = 585 billion cells. That is 718 billion cells below the recommended amount.

 

[MrCrabby]

Worst case scenario:
The initial underpitch stressed the lager yeast as it tried to reproduce to sufficient numbers to handle all the sugar. This would result in estery, unclean, and generally un-lager like flavors. This process would likely be finished by the time you added more yeast.
In addition, adding the S-05 means that this is no longer a Märzen (small point). Instead of the two yeast mixing and dividing their flavor contributions, one will overtake the other and win out (probably the lager yeast, since its numbers are built up by now). Or you may just get the worst of both worlds. Who knows?
S-05 also has been known to produce apricot-like flavors at the lower end of its temperature spectrum.

Now, these are just some worst-cases. All or none may happen, but that's why brewing is so exciting! Please report the results.

 

[drunkEnough4U]

**** it, hope it goes well brother. Looking forward to seeing how this went.

 

[Keiron]

Worst case scenario:
The initial underpitch stressed the lager yeast as it tried to reproduce to sufficient numbers to handle all the sugar. This would result in estery, unclean, and generally un-lager like flavors. This process would likely be finished by the time you added more yeast.
In addition, adding the S-05 means that this is no longer a Märzen (small point). Instead of the two yeast mixing and dividing their flavor contributions, one will overtake the other and win out (probably the lager yeast, since its numbers are built up by now). Or you may just get the worst of both worlds. Who knows?
S-05 also has been known to produce apricot-like flavors at the lower end of its temperature spectrum.

Now, these are just some worst-cases. All or none may happen, but that's why brewing is so exciting! Please report the results.

I pitched the US-05 4-5 hours after the W-34, so I'm guessing/hoping it didn't have time to get stressed.

What do you mean one will win out? How does this happen?

I'll post the results!