Is Oxygen My Problem?

Hi All:

My last 5 or 6 beers have been stalling out during fermentation. The last 3 big batches I have done started with a gravity of 1.099 or higher and then they stall out at around 1.040 to 1.050. The last 2 small batched I did stalled at about 5 points before the high end of it's projected final gravity. I never used to have this problem and so I was trying to think what may have changed in my brewing process to cause this. The only thing I can think of is I started using a plate chiller to cool my beer. Previously, I would use an immersion chiller and then splash the beer into the fermenter with a funnel. This always provided enough oxygen for my fermentation. After switching to the plate chiller, the only oxygen that gets in the beer now is the time it takes to fall from the carboy neck to the bottom. I have also put a sparge tip on the end of the hose to encourage more oxygen into the beer while it falls and splashes.

So the questions is: Do you think that since using the plate chiller, my beers are not getting enough oxygen?

I do double and sometimes triple yeast starters so I know there is viable amounts of yeast. I have just started filtering my water. Sanitize with StarSan. Ferment my ales at 65 - 67 F.

Any suggestions?

Thanks!

What yeast do you use?

It varied depending on the beer I brewed. Here is what I can remember:

Dopplebock: Belgian Lager (Wyeast) - Double starter
Dry Stout: Irish Ale (WL) - Single starter
Hoppy Brown Ale: S-05 - No starter
Belgian Dark Stront: Abbey Ale (WL) - Single starter

I would say yes, lack of proper aeration of the wort could definitely contribute to the issues you describe as you appear to be pitching the proper amount of yeast based upon OG per batch. o2 is necessary for the yeast during the lag phase after pitching and if it's not there the yeast are stressed to start.

IMO you should either be using an o2 set up or get an aquarium pump with a stone to get good aeration into the wort. Also, be sure your yeast strains can tolerate the amount of alcohol you are projecting as too much alcohol can stress some strains as they try to finish.

Ya I agree with duboman.

I think part of your problem is you're way under pitching/over stressing yeast for 1.099

also probably are having issues with aeration too... I use pure o2. I would look into it especially for that big of beer.

Well for the Dopplebock. I did a starter. drained the fluid. Added more wort, fermented that out. So essentially a double-starter (or at least that is what I call it).

Is that not enough yeast for a big batch of beer?

Thanks!

red131 said:

Well for the Dopplebock. I did a starter. drained the fluid. Added more wort, fermented that out. So essentially a double-starter (or at least that is what I call it). Is that not enough yeast for a big batch of beer? Thanks!

Click to expand...

Don't really know
Www.mrmalty.com or Www.yeastcalc.com would be good site to use to determine proper pitch rate.

Sounds to me like both.. That's not much oxygenation, and those are pretty big beers that need big yeasties.

Check out the Venturi style aeration method, several posts in the DIY section.. That might work well for you.

What's the alcohol tolerance of the yeast you used?

When I switched to a counterflow chiller, I added that venturi thingy. It's handy: the hose directs the wort into the fermentation bucket, and aerates it at the same time. I also use a petsmart aeration stone with petsmart hose, attached to a Home Depot oxygen welding tank thing, and a LHBS regulator (all in for about $45). And I've never failed to get below 1.015, even from 1.100, since I started aggressively oxygenating my wort. YMMV.

+1 on pure O2 use. With such a high-gravity beers, I'd hit them up twice with pure O2 - once at the point of pitching yeast & second time 12-16 hours later. Don't forget to add a bit extra yeast nutrients to the boil.

+1 on O2
My beer took a massive step forward with oxygen.

+1 on O2, all brewers who do big beers, lagers should do it.

Thanks everyone. This is what I have taken away from the discussion:

• Huge starters for large beers (or pitching beer on an existing yeast cake)
  
• Use direct O2
  
• Make sure the yeast I use can handle the alcohol tolerance and attenuate properly for my goal

Thanks!

There is a downside to using a forced aeration. Any oxygen that is not scrubbed from the wort during fermentation can cause the yeast culture to switch into respiraitive growth mode using ethanol as its carbon source at the end of fermentation. The phenomenon is known as diauxic shift.

With a 23.5P (1.099) wort, the yeast culture has deal high osmotic pressure at the the beginning of fermentation and high ethanol levels at the end of fermentation, which means that one needs to pitch a large number of healthy yeast cells in order to ensure full attenuation without producing a ton of metabolites. Worts of this gravity are best fermented with a large amount of freshly cropped yeast.