Should I oxygenate the wort for a tripel I'm pitching onto a yeast cake?

[DuncB]

I've brewed a 5 gallon batch of tafelbier 2.4% with wlp530 last weekend. This has finished and my plan was to keg this and then pitch the yeast for this into a 5 gallon 1.078 tripel I'm making this weekend.
There's about 300ml of settled yeast in the fermentasaurus collection bottle.
If I'd made a 3 litre starter I'd have far less yeast and would oxygenate before pitching.
Should I still oxygenate as normal?
Second question Am I right to oxygenate before pitching or after or does it make no difference?

 

[VikeMan]

How many cells do you reckon you have? I would not force pure O2 unless I needed yeast growth (i.e. to build cell walls for budding). Yeast may use small amounts of O2 for other purposes, but I suspect that just racking your new wort into the fermenter, plus headspace O2, would provide more than enough O2 for those needs.

 

[DuncB]

Thanks for the reply. I used a 1 litre starter for the 2.5% beer and it fermented in about 2 days for a 20 litre batch.
The yeast settled and there's a very clean looking 300 ml of yeast in the bottle at the bottom.
So I reckon a lot of cells and as you implicate no need to encourage more growth.
I'll just put the wort in the fermentasaurus and then add in the yeast as you suggest. I'll update.
Thank you

 

[day_trippr]

fwiw, I generally aim to pitch a roughly 300-350 ml volume of post-crash well decanted starter yeast, so not much in the way of trub and rather tightly settled. If your collection approaches that you're likely in good shape - though I always oxygenate my worts regardless of yeast strain/amount/expected viability...

 

[IslandLizard]

I've been thinking about it, and wasn't sure either.

Too bad Mr. Malty's calculator hasn't recovered yet... That "re-pitch from slurry" tab comes in handy.

So, let's do it by hand:
According to BrewUnited's yeast calculator, you'd need to pitch 298 billion cells. (5.5 gallon batch @1.078).
Your 300 ml harvested yeast slurry easily contains an estimated 50% trub, could be better, could be worse, you'd be the judge.
That brings you to only 150ml of actual yeast, at best, roughly the equivalent of 3 vials or Purepitch packs, about 300 billion cells total, and quite fresh.

On first impression, @VikeMan's suggestion makes sense, 300 cells looks about right. To pitch that is.
Then comes @day_trippr's argument...

Yes, you want to pitch a boatload of good, healthy, vital cells (300 billion per that calculator). And, yup, you've got them: ✓ Check #1!

But... the yeast will need oxygen to grow more healthy cells to bring this new batch to completion. Both your harvested slurry and your freshly boiled, then chilled, batch tomorrow contain zero oxygen.

So, yes, You need to oxygenate, to a regular 8-12 ppm, yup! ✓ Check #2!
That's what I've always done too, even when pitching large, fresh starters, and never found any problems.

The yeast will use up the oxygen she needs/can, the rest will be blown off with the CO2 when active fermentation starts, as usual.

For high gravity ales, even a 2nd oxygenation is recommended.*
This 2nd one needs to be done 12-18 hours after pitching, but before active fermentation has started. Finding the right time for the 2nd oxygenation has proven to be most difficult. I bet we'd easily miss half of those, especially after the 18-hour checkpoint.

So if no activity is happening after 12-18 hours, I'd give her a 2nd oxygenation session too.
Just don't overdo it.

* I would consider 1.078 a high gravity ale.

 

[DuncB]

Thank you, so possibly enough cells, but their longevity for a high / higher gravity brew is uncalculable.
I've done the second oxygenation for an English barley wine in the past with an OG of 1.107, but didn't bother with an imperial stout of similar gravity or my second go at the barley wine with a higher gravity ( due to better technique) of 1.127.
However that was WLP099 super high gravity ale yeast and it really went crazy with a barm or krausen you could have stood on. But I did oxygenate well at the pitching for the large starters.
I'll oxygenate after pitching and the yeast can use any dead cells for extra nutrition, I will still use yeast nutrient.
If I see no gas the following day I'll give another blast of oxygen.
Thank you all.

 

[IslandLizard]

so possibly enough cells, but their longevity for a high / higher gravity brew is uncalculable.

Enough cells to pitch, yes.

Yet, they still need to multiply* to get the job done. In higher gravity worts that is more of a chore for the yeast. So we need to build an extra reserve into the pitch, and surely prevent underpitching. And provide ample oxygenation to help with better/more growth.

* We therefore typically see a yeast growth of 3-5 times from the pitched amount.

 

[VikeMan]

The yeast will use up the oxygen she needs/can, the rest will be blown off with the CO2 when active fermentation starts, as usual.

But excess oxygen will not all be blown off. Some of it will have already participated in oxidation of wort compounds. I'm pretty sure you know that, but I didn't want future googlers thinking that it's impossible to over oxygenate wort.

 

[hottpeper13]

To get the amount of cells in a yeast cake I go to Brew Dad's calculator and input my numbers for the first gen starter. It tells you how many cells you need and the size of the starter. Next input the numbers for the beer you're brewing in the second step section. It will give you the growth rate(most important) and the number of cells in the slurry. Doesn't matter about the trub,the cell number is the cell number! Just take the number of cells you need for the next beer and divide that into the cell number and you have how many batches you can pitch onto.
As far as pitching before or after O2, I read a paper where a brewery was having sensory issues and thought that because the ppm's of O2 were low they kept upping it. The end result was that they were measuring the O2 in the FV right at the inlet. when they put another sensor after the O2 injection but before the yeast injection. Set it to 8 ppm's and sensory was right on,even though the FV sensor still read close to 0. Since that paper I've been pitching the O2 and stir for what ever time needed for the OG,and there is barely any foam on the surface.

 

[IslandLizard]

But excess oxygen will not all be blown off. Some of it will have already participated in oxidation of wort compounds. I'm pretty sure you know that, but I didn't want future googlers thinking that it's impossible to over oxygenate wort.

I agree that over-oxygenating can be as bad as under-doing it. It's just going to show in a different way (through oxidized wort).
But 8 ppm isn't overkill in the OP's case, the pitched yeast, being just a harvested slurry, can and will use that up. No?

If no, can we better estimate to what level (ppm) it needs to be oxygenated, so there will be less excess, or better, none?

The end result was that they were measuring the O2 in the FV right at the inlet. when they put another sensor after the O2 injection but before the yeast injection. Set it to 8 ppm's and sensory was right on,even though the FV sensor still read close to 0.

That's an interesting notion!
It seems to show us that O2 is absorbed by the yeast that fast.
Does it also tell us anything about the O2 that wasn't absorbed by the yeast?

 

[hottpeper13]

I would think a reading of 0 in the FV means 0. Of course the measurement is in ppm where finished beer is measured in ppb,so there might be a small amount not absorbed.

 

[DuncB]

Just an update, I pitched the yeast / slurry into the 1.074 wort at 16C then oxygenated with 90% oxygen for 150 seconds. By the time I'd tidied up I could see some bubbles rising in the collection bottle at the bottom of the fermentasaurus.
Picture of the krausen or barm at 4 hours.

We'll see how it goes, certainly smells fruity so far.

 

[Bassman2003]

Glad to see it took off. I was expecting a positive outcome since the cells were so fresh. I have come to think vitality is more important the numbers. In the book "Brew Like a Monk", Stan H. said the monasteries pitched a scary low rate but their yeast was so fresh that it mowed through the wort.

 

[DuncB]

I think as well they were hungry having only been in 1.024 gravity wort just enough to multiply but not much fun for them after that.
It smells great / belgian.