Stir Plate Starter Quality

[floppinab]

My good friends.

I've been using stir plated starters for all my brews for a while and by and large they've worked OK but I'm occasionally getting ferment issues.
Thing is I very rarely get what I think are strong ferments in the starter and although the starter wort ferments out I suspect I'm not getting enough yeast growth and therefore not creating enough yeast in the starter. I can't remember seeing anything like a krausen on the starters I make. Is this common or should a stir plated starter see at least some level of krausen or does the stir action "pull down" the krausen that would normally form????

My method is as follows.
I usually make a couple of extra litres of my target AG brew, that goes into a sterilised plastic juice bottle and into the fridge. I've been splitting a Wyeast or WL packet 5 ways into tubes that get stored in the fridge, one of these is the starting point that goes into the Erl. flask. I will then decant off around 300ml out of the juice bottle into another small sterilised vessel. Depending on the OG of the wort I will then water that down (with warm tap water to match the temp of the starter) to get a target OG of around 1.030. That gets sealed and I'll shake the **** out of it for around 10 mins. It then goes into the flask and the plate gets started up. The Erl flask gets a loose covering of sterilised alfoil.
I will then step up the starter 3 or 4 times over the next 3 or 4 days (using the same method of wort addition) and finish with a 2 litre starter for ales or up to around 3 litres for lagers. The flask will then go into the fridge for a day, the majority of the starter solution then decanted off to leave around 200/300 ml of yeast solution, that then left to slowly pull up to the target pitch temp prior to pitching.

I've been thinking that if there is an issue it has to be one of oxygenation but I would of thought my methods should be getting enough O2 into the starter for a decent level of yeast reproduction. I've been thinking of trying the olive oil method but have seen mixed reports about using this.

Any thoughts appreciated.

 

[raven19]

Method appears sound.

However, ideally you are trying to pitch your starter into your wort at the peak of fermentation (high krausen). So by placing your larger starter into the fridge, you are slowing the yeast down, dropping most of it out of solution - then pitching this slowed down yeast into your wort, hence it has to wake up again prior to doing its thing.

I would be pitching your starter straight into your wort after 18 - 24 hours ideally.

2c.

 

[Sammus]

Are you sure all the yeast is dropping out? Particularly with Lager yeasts, I've left them in the fridge for up to a week and had mainly trub and dead yeast drop out, most of the yeast still in suspension. You have a fairly good idea - if they yeast has dropped out the wort above it should be crystal clear. The yeast layer on the bottom will be white, any other colours are impurities or dead yeast. I never decant mine and I've never had a fermentation issue (not on the ones I've made a starter for anyway ).

Another thing that's springs to mind is that 4 steps from 300ml to 3L is quite a lot. Everything I've read suggests the optimum step up for reproductive purposes is between 5x and 10x, so you could go 300 straight to 2 or 3L. Apparently any more or less and the yeast is too stressed because theres so much yeast and not enough food to go around, or there's too much food and they get lazy and dont both reproducing.

http://www.mrmalty.com/calc/calc.html suggests that for a single step, to get enough yeast to innoc 23L of 1.048 ale wort, two of those vials (ie 40% of the yeast) into a 2.5L starter would do it. That is of course assuming your yeast is 100% viable (which it probably isn't). There is also a different calculator on the wyeast homepage (link) which estimates the viable yeast cell count after multiple step starters. I usualy use the MrMalty calc to determine the kind of yeast cell count I need (in this case, 205 billion) then use the Wyeast calculator to figure out what steps I need to make.

Well I used to, until I realised that it's way too much effort, and I get just as good results even with a fraction of the 'recommended' pitching rate. But I guess my point is, playing around with those calculators (constantly converting betweel gallons and Ls when using the wyeast one is a bit annoying) you can get an idea of how far you are off what the pros recommend.

eg, assuming your yeast is 100% viable, pitching 1/5 of a pack into 300mls (0.08gal) on a stir plate, then when that's fermented, pitching it into 3L (0.8gal) of wort on a stir plate. The wyeast calc tells us at the end of that, you have 0.88gal (3300ml) of wort, with 13.29million cells per ml, or nearly 44 billion yeast cells. Not quite the 200+ recommended, and that's if you're not decanting any from the starter.

Another thing (sorry ) to consider is that with ales, it isn't really necessary to decant all the wort, and in fact could be beneficial to pitch at its most active (high krausen, a bit hard to tell on a stir plate). I was concerned about this when I started yeast farming and asked the board and got the feeling that most people didnt notice any difference pitching some stirplated wort in with their main batch. Lagers are a different matter though, you want to try and pitch slurry only.

I hope some of that help a little anyway.

Cheers

Sam

 

[mickoz]

Another thing (sorry ) to consider is that with ales, it isn't really necessary to decant all the wort, and in fact could be beneficial to pitch at its most active (high krausen, a bit hard to tell on a stir plate). I was concerned about this when I started yeast farming and asked the board and got the feeling that most people didnt notice any difference pitching some stirplated wort in with their main batch. Lagers are a different matter though, you want to try and pitch slurry only.

+1 on that. If you chill it down to settle and pour off the beer on top the yeast is dormant. I would pitch it while it is active for an ale.
Also I would worry about infection if you are adding warm tap water to your starter? Do you boil it first?

Mick

 

[braufrau]

Hmph! I've been decanting because of stuff people have been saying here .. gonna go back to pitching the whole lot again!

 

[floppinab]

Thanks for the replies, much appreciated. I think I may have found my problem. After trawling through the TASP thread I realised that most have their plates running pretty fast with a sizeable vortex in them. I had thought I would be putting enough O2 into the wort prior to putting it into the flask and that plates main function was to keep the yeast in suspension. It seems that is probably not correct in that to really get the starter firing you need the plate speed up pretty high to give that continual feed of O2. I had a starter which I pitched last night and stepped up this morning, I upped the plate speed and sure enough when I checked 30 mins ago there was a nice krausen of around 5 or so cm.

Are you sure all the yeast is dropping out? Particularly with Lager yeasts, I've left them in the fridge for up to a week and had mainly trub and dead yeast drop out, most of the yeast still in suspension. You have a fairly good idea - if they yeast has dropped out the wort above it should be crystal clear. The yeast layer on the bottom will be white, any other colours are impurities or dead yeast. I never decant mine and I've never had a fermentation issue (not on the ones I've made a starter for anyway ).

I'm pretty sure the vast majority has dropped out Sam, the wort I pour off is pretty clear. No doubt I am losing some of the yeast but I'd be surprised if it was more than say 10%.

Another thing (sorry ) to consider is that with ales, it isn't really necessary to decant all the wort, and in fact could be beneficial to pitch at its most active (high krausen, a bit hard to tell on a stir plate). I was concerned about this when I started yeast farming and asked the board and got the feeling that most people didnt notice any difference pitching some stirplated wort in with their main batch. Lagers are a different matter though, you want to try and pitch slurry only.

I hope some of that help a little anyway.

Cheers

Sam

Thanks for the info on calculators, was aware of some of that. Re. the Ales, the main reason I have been doing that was some anecdotal evidence suggesting pitching that much of a starter solution can introduce a lot of the undesirable flavour profile of the starter into your final beer. I don't see too much difference in chilling an ale yeast down for 24 hours then waking it back up again compared to having a White Labs vial which has been kept refrigerated then bringing that out warming it up then pitching it.

 

[Stuster]

Also I would worry about infection if you are adding warm tap water to your starter? Do you boil it first?

Glad you seem to have sorted out the issue, Gav. I'd also be worried about using straight tap water in your starter though. Is it boiled first? :huh:

 

[floppinab]

Glad you seem to have sorted out the issue, Gav. I'd also be worried about using straight tap water in your starter though. Is it boiled first? :huh:

Ah yes, forgot to answer that one, well harking back to my K&K days when I can't remember boiling 20 odd litres into the ferm with the can of goo, I thought why bother???

But on second thought given the propagatative nature of having a starter (and .....ahem.......given my last starter had a slight infection and ended up in the bin), it's probably a good idea................ will get the kettle out in future.

 

[braufrau]

I always boil, or sometimes pressure cook, my starter, malt and all. Before adding the yeast ... obviously!