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Joelle
07/12/07 11:49 AM  
How to make a continual minamalist feeding starter
Hi guys. I'm thinking about trying to make a continual minimalist feeding stir plate air injection starter the way Ubriaco described awhile back. I have a few questions though. Here's how he described his method:

"My initial source was my glycerol stock in the -80C, I took a 10uL aliquot and built it. By the time I took it home and put it on the stir plate/aerator it was a 40mL saturated solution pitched into 200mL of 20g/L sugar, 3g/L yeast extract, 3g/L casein, 3g/L malt extract. From there I used my home starter media which consists of 20g/L sugar, 3g/L malt extract, and 3g/L yeast nutrient. I hit my starter with 50mL of this solution 3-4 times a day for one week. This culture was used on a 5 gallon batch."

First, for the "home starter media," when he's referring to 20g/L sugar would this be corn sugar? Then on to the process, should I start with 200mL of the starter media, toss in my vial of yeast and put it on the stir plate? Then start feeding it with 50mL of the starter media 3 or 4 times a day? Also, how should the starter media be stored? Would it be OK to leave it in the fridge in a sanitized glass jar? If I kept it that way, would I want to warm it to room temp before adding it to the starter on the stir plate? Thanks for the help. If you can't tell, I never took a microbiology class that had a lab component!

Joelle

Baums
07/13/07 11:13 AM  
Re: How to make a continual minamalist feeding sta
I am not sure how Ubriaco does this without introducing infection... maybe he uses a squeeze bottle or something, or maybe he sterilizes each addition on its own.

But let me put his method in context.

If you give a "normal" starter continuous air (via either a stir plate or sterile air pumped in with a stone) then you will grow about 100 billion cells in one liter of 1.040 starter wort. The cells will be very healthy (in the sense that they will be well stocked with sterols/UFAs).

The "standard" US microbrew pitching rate is, of course, about 1 billion cells per liter per degree Plato. (There are reasons you might want to use more or less than this, but that's another discussion.) That's 247 B cells in a 19L (5 gallon) batch at 13 plato (1.052 SG). You could get that from a 2.5 L aerated starter. Or from doing a 1.25 L starter, and pitching that yeast into another 1.25L starter. Or whatever.

The point of Ubriaco's method is to grow MORE than 100 billion cells per liter, by creating certain growth conditions. I don't know how much more he gets, but maybe he does. Anyway for him, that's worth whatever effort is involved--and he may have some way that doesn't take much effort.

N8
07/13/07 11:19 AM  
Re: How to make a continual minamalist feeding sta
I would think that using dextrose would be fine.

As to how to get this started, I haven't tried this process, so I can't speak from any experience, but I would think that using starter media would be ok, unless you can come up with the other components to make up the solution that is mentioned prior to the starter media, casein, yeast extract,etc. Yes, put it on the stir plate, be sure to put in the stir bar. ;) I've had a guy ask me from my beer club why his stir plate doesn't work. After several questions, I asked how big the stir bar was. He said, "what stir bar?" hehehe :) They work alot better with them in the flask...

Anyway,.

I think that after a day of stirring to get the yeast awake start adding the 50 ml 3or4 times a day.

Prolly best to keep it in the fridge in an as sterile as you can keep it jar. No need to warm before adding. Might help contribute to the production of F.A.N (Free Amino Nitrogen)

Joelle
07/13/07 12:08 PM  
Re: How to make a continual minamalist feeding sta
Thanks for the pointers guys, and yes I do have a stir bar. :^) Sounds like a 2.5L starter will be enough for a regular beer without the trouble of continuous feeding. I have another question though. Baums says:

:The "standard" US microbrew pitching rate is, of course, about 1 billion cells per liter per degree Plato. (There are reasons you might want to use more or less than this, but that's another discussion.) That's 247 B cells in a 19L (5 gallon) batch at 13 plato (1.052 SG). You could get that from a 2.5 L aerated starter. Or from doing a 1.25 L starter, and pitching that yeast into another 1.25L starter. Or whatever."

Do you think there is a difference in the amount of cells you get by just pitching your yeast into a 2.5L starter on the stir plate and splitting your 2.5L starter in half, letting it run on the stir plate and then pitching in the other 1.25L starter to what you have going on the stir plate? If not, then I don't see why you should bother with splitting it up. Just curious.

One other thing. How long does it take for the yeast in a starter on a stir plate to use up the sugars in a 2.5L starter? I want to decant the liquid off the top of the yeast before pitching it.

Joelle

Baums
07/13/07 01:11 PM  
Re: How to make a continual minamalist feeding sta
Not a difference worth worrying about--I only mentioned it because some people don't have a vessel that can hold a 2.5 L starter.

And by the way, for many ale strains, half the standard rate (or even less in some cases) is adequate or even preferable (increased esters).

How long will it take? Well, first make sure you pitch plenty of yeast into the 2.5L (or whatever) starter. A commercial packet/tube is PLENTY, or if you are growing it up from a slant then your previous step should* probably have been about 1/10 the size: 250 mL. If you do this then I find that 2 days is plenty. There should be no foam on top of the wort, and when you stop stirring, the yeast should begin settling noticably within a few hours.

*Some people think that for a homebrewer, there is more infection danger in doing lots of 10X step ups (where you are handling and opening stuff a lot) than there is in just doing one huge step up (in which it is harder for the initial yeast to dominate any trespassers). They might be right.

Joelle
07/13/07 01:27 PM  
Re: How to make a continual minamalist feeding sta
Thanks Baums, that's the info I needed. Yeah, you're right about wanting to underpitch beers where you are looking for more esters. The 2.5L starter would be one I could use for clean ales of moderate OG or maybe bigger Belgians. I was interested in Ubriaco's method for lagers (especially higher OG ones) where I needed a ton of yeast.

Joelle

 
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