Yeast Starter - How big and how long?

[gedburg101]

Hi guys,

I'm not far away from stepping up to a bigger kit (hopefully 200l should her in doors allow me sole use of the new garage) but the I tend to use liquid yeasts. Buying liquid yeasts for brew in that volume becomes pretty expensive and I feel that starters would be the way forward. I've never made a starter before...

I built a DIY stir plate that worked well but with the house move I've not really be able (or allowed...) to do any brewing recently to trial it out in action.

Question is;

1) Can I grow a starter from one or two packs of liquid yeast to be enough to ferment 180l of beer;

2) If yes, how big a flask do you think I'd need and how much DME etc;

3) How long would it take to do get the cell count high enough?

Thanks in advance.

 

[JapanBrew]

It's not a flask you'll use but a small 10 liter corny keg. But you will have to step it up several times by halving and halving. You'll need lots of oxygen and lots of nutrients. I have never gone that big so that's about as far as my advice can go.

 

[MyQul]

The other alternative you could do is make a regular 23L batch using 1 pack of liquid yeast.Then harvest the yeast cake and put the whole thing in your 200L brew

 

[IainM]

I suggest you use a pitching rate calculator like the brewers friend one, or mr. malty.

 

[Zephyr259]

I was curious so I ran the numbers through my spreadsheet. Assumptions I made were that you're starting gravity was 1.05 and you're pitching at 0.75 (million cells/mL/°P) target for 180L is 1672 billion cells. I've set it to manually shaken for aeration as with these large starter volumes I doubt your stir plate is going to be as effective as one would be with 1 - 2 L starters. Or have you built and industrial scale monster stirrer?

Starting with 2 packs of yeast fresh from the supplier (97% viability - 194 B cells) you can pitch into 7.5 l of wort (818 g DME) and get 701 B. Then pitching this into 14.5 l wort (1582 g DME) gives 1682 B cells.

If your stir plate is sized appropriately then the way the maths works your actually better starting from 1 pack (97B cells) and going 3.5L then 7L to give 1701B cells.

Of course the packs are never that fresh by the time we get them but this should give you an idea and it satisfied my curiosity about such a big brew.

Good Luck. :-)

 

[gedburg101]

So you could have all you need in 7l of starter (I know that's still huge)?

Fetch me a desk fan! I've got a stir plate to build!

 

[Zephyr259]

I like you're optimism. :-)

Some more info, if your yeast is 2 months old, viability will be around 62%. I pack with a stir plate will require a 2L started followed by a 9L starter.

This is all assuming 1.050 OG. Being able to grow a 15L starter should let you propagate yeast for most beers. My test was 180L of 1.080 OG at a pitching rate of 1 million cells per ml per plato. Takes 3 steps that one, but then you are brewing 180L of near barleywine...

Here's the spreadsheet I use, I have the downloaded excel version. I use it to calc starter volumes as I use the overbuild function to grow an extra 100B cells which I then keep for my next batch. Seems to work pretty well thus far.

http://www.brewunited.com/yeast_calculator.php

Upon a moment's thought it might just be easier to brew a standard 23 L batch and use it's yeast cake? Not sure the calculator is that accurate for that though. Pitching 100B cells into 23 L of 1.04 wort with no aeration gives about 1000B cells at the end. I know other pitch slurry maybe they could advise on the amounts used?

 

[Simonh82]

For starters that big the cost of DME is going to get pretty expensive. I would save (freeze if possible) some wort from your previous brew to use in your starters. Maybe you could make the initial step with DME and then when you step it up to 10L or whatever you could use your wort.

If you keg (and I guess you aren't planning on bottling 180L, then you can use a stir-bar in the bottom of a corny keg, see this Brulosophy experiment for an example.