YEAST GROWING ISSUES Ideally stirplate users only

[shuggie159]

I have a stir plate and am no novice brewer, yet successfully cultivating my own yeast is still a bit of a mystery to me.

I am aware I need to pitch with at least 200billion cells for a 22 lit brewlength. The problem is I loose count at about 20! Yeh! What does 200 billion look like?

My process has been to grow-on the dregs of a bottle conditioned ale in 25ml - 250 ml - and then 2 litres on a stir plate. That is a ten fold re-growth ratio which in therory should maximise the growth. Beyond 2 litres (in a DJ) the stirplate doesn't work. For each iteration I monitor the brix starting at about 11.2% and transfer at about 7% (1.040 - 1.020). If I leave it on the stirplate to ferment out longer I have had iffy results in the past (oxygenation ?) Anyway, this finally produces about an eggcup full of creamy slurry in about 5-6 days. My gut feeling is that this is still woefully light on the perceived Mr Malty pitching ratios. I would rather over-pitch than under. Anybody with a stirplate got any pointers on where to go from here. I have a nagging doubt that I may need to invest in another stirplate.

I would like to develop an empirical process that needs little external monitoring, such that I could start a yeast cultivation process in the sure knowledge that in ,say a week's time, I would have a healthy yeast population.

What do other stirplate users do?
i.e. how much slurry do you make and what steps do you take to cultivate it?

Cheers guys...

 

[Aleman]

Get a better stir plate

Mine (which is rated to 1L) will quite happily stir 5L in a conical flask I haven't gone much bigger than that simply because I don't have any bigger vessels that I could use.

For most 20-30L batches I try and pitch around 100l of thick slurry, which I can easily achieve using a 2L volume.

My procedure is from a single colony into 2ml of 1.020 wort, within 24 hours this is fermenting so it goes into 20ml of 1.020 wort . . . again 24hours later it's actively fermenting so into 200ml of 1.020 wort on the stir plate and I start feeding sterile filtered air into the flask (not the wort), once actively fermenting that goes into 2000L of 1.035-1.040 wort again with air and stirring . . . that is allowed to ferment out, and is then crash cooled off the stir plate.

I can easily get 250-500ml (depending on strain) of yeast slurry using this method . . .For Lagers I go up to 5L . . . I also go 1L to 5L when I get a new Whitelabs Tube

 

[shuggie159]

I'm re-assured that, with the exception of your pumped filtered air, our process's are fairly similar. So I'm on the right track.

There are two issues with going to a bigger flask. The whirlpool doesn't reach the magnet above about 100mm depth, which thought was the magic bit about a stirplate; and secondly the base of the larger flasks is usually less even causing the magnets to bounce and eventually spin-out if the rpm is set too high.

Possibly we are at odds on the definition of slurry. I mean a thickish gloop achieved when the contents of the flask has rested/crash-cooled. I can only get about 5% gloop out of the completed fermentation of 2 litres i.e. about 100ml or less. OK a bit more than an eggcup full but not much more. But possibly that is irrelevant. The real question is how many yeast cells does a 2 litre process, similar to what we have both described, represent?

 

[BrotherMalice]

I dont know much about this my self but have you got/read Jamil's yeast book?
I have not read it yet but it may be worth a go if you can get hold of it?

 

[Aleman]

The real question is how many yeast cells does a 2 litre process, similar to what we have both described, represent?

The only way to be sure is to equip yourself with a microscope, and a Haemocytometer slide and indulge in counting the blooming things. . . . You will also need to be able to do serial dilutions (accurately) . . . Jamil's book is good for this sort of thing . . . Although I like Pierre Rajottes "First Steps in Yeast Culture" as a Lab Techniques book

 

[jonnymorris]

The real question is how many yeast cells does a 2 litre process, similar to what we have both described, represent?

You could approximate by comparing the volume and viscosity of your yeast slurry to a white labs vial which contains 100billion cells.

 

[dennisdk2000]

How about investing in a 5L conical flask? You might find that the stirrer plate works better with a container with a flat bottom.

Dennis

 

[anthonyUK]

Definitely get the Yeast book mentioned.
It is hard going but invaluable.
One thing to consider is that when stepping up the cell growth curve is far from linear.

I don't know how useful it is but there is a yeast calculator which might be worth a try at http://www.yeastcalc.com/

I found it via this article - http://braukaiser.com/blog/blog/2012/11 ... st-growth/

 

[shuggie159]

Thank you. Nice one guys.

Yes I have the book. Good info. and for a while was a bed time read for a week or so (just confirming to my wife I'm a little odd) But too be honest a bit too techie when it got the theory on propogation rates etc.

I used it to help develop my technique, and it seems to have helped conciderably there. I just needed reassurance that I was doing what others were.

The links to the yeast calculators = well good.