Stir Plate And Whirlpooling

[Wolfy]

wWhen is it right to stop the plate and let them ferment out? Will they still build their glycogen and trehlose reserves if they are still getting the o2 from the plate?

Most yeast should achieve (close enough to) maximum growth after 12-48h on the stir-plate, then they need a bit more time to complete fermenting, as they are finishing that (I thought) is when they build up the food-reserves (which is one reason I like to let my starters fully ferment and settle before pitching).

 

[Yob]

then they need a bit more time to complete fermenting, as they are finishing that (I thought) is when they build up the food-reserves (which is one reason I like to let my starters fully ferment and settle befre pitching).

this ^^^^ is what I settled on.. flicked off and left to their own devices..

I tell ya, much easier pitching rinsed yeast (all this for 15ml?)

...not half as much fun as the stirplate though :lol:

:icon_cheers:

 

[kieran]

Does it make any difference if the "Whirlpool" reaches the bottom of the flask or not.

Not really, but you're increasing the surface area contact between the liquid and air which is always a good thing for metabolism when there's yeast in said liquid.

OT
When making cultures, and alternative method is to use an orbital shaker, which gives a similar resulting vortex in the flask. However, a difference is that you can generally go faster, and you can further improve aeration by using a baffled conical flask which disrupts the vortical flow, but generates a lot of turbulence and splashing. That further improves oxygenation, and yeast (and bacteria) love it. Off topic, but I guess there's probably a few people out there with orbital shakers in AHB land though..

 

[Charst]

Im experiencing the same thing Yob having regarding quick krausen times. Trying to make enough yeast to pitch into 2 batches

Using YeastCalc.com I stepped 11 billion (Viable) into a 500ml starter, On the stir plate for a few days and once krausen was gone and no more bubbles I Chilled, decanted. Calculated 50 Billion Finish

Step 2: 50 Billion Viable into 1.5 litres (lag was hours) in my 3L ErylenMeyer for a few days, Crashed for 24-36 hours, decanted wort (left yeast in EMFlask. Calculated 190 Billion Finish

Step 3: 190 Billion Viable, Added 1.5 litres of wort boiled in Pot into EM Flask (Lag was about 1 hour h34r: ) Calculated 391 Billion Finish.


Question Is: If I was to pitch this last step at High Krausen, i.e. now, 1 hour after feeding crashed step 2 more wort, surely im not at my required 391 Billion. Surely its just the Step 2 yeast going more food bang and into it. The only way I can Guarantee (ISH) I have the right amount is to wait to ferment is finished, crash, decant and pitch slurry isn't it?

Which to my mind calls into question ever pitching at high krausen?

I guess this question wouldn't come up if I had a 8 hour lag on my starter I'd probably say yay High Krasuesn here and pitch away, but after 1 hour.
Meanwhile ive added foam control twice to try knock back the head on it but its still an inch and a half high, thinking im going to lose a few billion over night out the top.

no no - growth wont be done by then... maybe its a bit past the point where its useful to give it more oxygen once its got karusen going, I'd probably not bother.

mind you, I've never gotten, nor am i sure I'd want that much activity so soon.... that'd kind of freak me out. There's supposed to be some sort of lag phase, and I dont know where your's has gone. I genuinely have no idea whether hitting krausen that fast is a good or bad thing, but its not bloody normal thats for sure, or at least not in my experience.

healthy ******* yeast I guess.

 

[goid]

Charst,

I don't have too much experience with building starters. But reading up about the process I can give a bit of an answer to your questions.

Question Is: If I was to pitch this last step at High Krausen, i.e. now, 1 hour after feeding crashed step 2 more wort, surely im not at my required 391 Billion. Surely its just the Step 2 yeast going more food bang and into it. The only way I can Guarantee (ISH) I have the right amount is to wait to ferment is finished, crash, decant and pitch slurry isn't it?

It is mentioned in the book "Yeast" that you will find little growth in quanity of yeast if pitching into too little wort. E.g. You are not stepping up at all by doing a 1.5l starter and decanting then pitching that yeast back into 1.5l of wort.

I would at this step only pitch a portion of the yeast from first starter into second.


Goid

 

[Yob]

The only way I can Guarantee (ISH) I have the right amount is to wait to ferment is finished, crash, decant and pitch slurry isn't it?

Being right propper shite at maths, I find that crashing it allows me to measure the quantity of yeast I have, this way I can simply use the Mr Malty "Thick Slurry" option and get me into the park.

Sure takes a few extra days but I think the process suits me better.

:icon_cheers:

 

[Charst]

See what your saying Gold but im not looking for a 10x growth which is considered a max potential growth step in starters,
Im only looking for a doubling in the last step..

If I decanted and only pitched a portion I would have too guess how much yeast I am pitching into the new starter, and basically reset the Yeast calc's Calcs to get an estimate of what total yeast I end up with.

In my way im leaving the guess work (viable yeast count based on production date) to the yeast calc software,

Pic Below shows Yeastcalc.coms Calculations from first step to last.

EDIT: Yeast Calcs Production date is in american talk. ie production date was really the 2/6/12

 

[Wolfy]

Pic Below shows Yeastcalc.coms Calculations from first step to last.

EDIT: Yeast Calcs Production date is in american talk. ie production date was really the 2/6/12

I don't understand the logic with those numbers (or the procedure) determined by the last steps of that calculator.

For example Dr Chris White (on various TBN podcasts) has said (multiple times) that pitching a full pack of yeast (~100billion cells) into a small sized starter (~500ml - 1L) results in virtually no yeast growth because all the nutrients are consumed so quickly. Yet you are apparently doing something very similar by pitching 190billion cells into a 1.5L starter and yet expecting a significant amount of growth. Shouldn't a growth factor of 1.05 indicate that there is 5% cell growth at that last step (190 x 1.05) resulting in 200billion cells total not the 205% growth (190 x 2.05) to finish with 390billion cells.

If you have 190billion cells at the next to last step (which is about double than in a fresh pack of shop-purchased yeast) which is more than enough to ferment a full batch of (standard size, standard gravity) beer, and then pitch all those healthy and active cells into such a small (1.5L) starter ... do you really expect to grow another 200 billion cells?
Obviously without cell-counts it's impossible to determine what is going on (and I could well be wrong), and if you trust the calculator (it's maths and the theory it is based on) to estimate what is going on, then it should all be good. However - if you ask me - it's another case trusting complicated (and flawed) mathematical estimates - when logic and common sense suggests otherwise.

 

[Dazza88]

my last stepped starter was 1.1l then 1.6l steps, i have 2l flasks. such a step is not ideal for much growth according to those experts in the know, as mentioned and quoted above, but yeast calc suggested it would get my required count and the creamy white layer of yeast was much larger from after the first step to after the last step. dont know if this a reliable indicator of growth but the beer it fermented was done in a few days. krausen appeared within 3 hours.

pacman yeast btw. great yeast.

 

[Charst]

I don't understand the logic with those numbers (or the procedure) determined by the last steps of that calculator.

I see your point wolfy, funny thing is id considered splitting the yeast after the 2nd step in order to build enough yeast to pitch into the double batch.

I emailed the yeast calc bloke the same details I posted here and ill see if he comes back.

Cant see why the yeast calc would come up with 2 differing figures i.e.. 390 billion built but only 1.05 growth factor.
in any case i have 200 billion very healthy yeast ATM.

 

[symphony1975]

sorry ti hijack thread and be :icon_offtopic: but thought seeing as guys in this thread own one......where did you get your stir plate from? is it a kit fixed into a plastic container? cheers

and again.. :icon_offtopic:

 

[Yob]

I bought mine off a fellow member here but they are easy enough to build.. Im on the phone so cant link it for you but do a search for tightarse stirplate, its a build tutorial by wolfy... Or wait till one comes up for sale..

Cheers

 

[goid]

Charst,

I had it in my head that at each step that the population of yeast would get close to peak of population in that volume of starter. This isn't the case though. By adding results from a starter to same size starter will still get growth but the percentage of growth goes down. As the calculator sugests. After reading it looks like once you get to the 200 million/milliltres innocculation rate the growth percentage is very low.


The way i was thinking and looking at those figures, if you after second step you take 50 billion cells and innoculate another 1.5l starter. You would end up with 190 billions cells plus the left over 140 billion. Giving you a total of 330 billions cells.

Or as the calculator works out that you can just put the 190 billion cells into another 1.5l starter and create 390 billion.

I would go the easy way and better results and go the second. (If the calculator was correct)


Goid

EDIT: The maths is doing my head in this morning. The last step in the calculator seems wrong at second look. Appears it should be 0.5.

 

[goid]

Just to add to my previous post and correct my edit.

The third step seems to me that the increase in yeast population should by at 1.5 (150% increase). This would give the third step a result of: 285 billion cells.

The growth values I was getting out of the book "Yeast" were from a test on a normal starter without stiring/agitation. So with using a stir plate you could expect a little more growth but to be conservative you could be getting at least the referenced growth. As Wolfy mentioned earlier, without actually counting cells the results can only be roughly estimated.


Goid