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Brews & Views Bulletin Board Service * Brews and Views Archive 2004 * January 9, 2004 * Yeast Starter Question < Previous Next >

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BrewMonkey (205.188.208.75)
Posted on Tuesday, December 16, 2003 - 04:51 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I make a yeast starter in a 1000 ml flask using 1 cup of light DME and 750 ml of water and ferment on a magnetic stir plate.
If I made a smaller starter in a 500 ml flask then stepped up to the 1000 ml flask, would this produce more yeast or just be a waste of time?
Also, just wondering how others make their starters.
 

Bill Pierce (24.141.63.119)
Posted on Tuesday, December 16, 2003 - 05:25 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

The general rule of thumb is to increase the starter volume 8-10 times between steps. This represents a good compromise between the population increase and stress on the yeast. On a stir plate the population increase is even greater, more like 15 times.

You can double the size of the starter between steps but the efficiency in terms of population increase for the effort is not very great. Why not do about the same amount of work and produce more yeast?

For a small (50 ml) smack pack, first make a starter of about 500 ml or a little less. Then step it up to about a gallon or so if you need a larger population, such as for a high gravity beer or batches larger than 5 gallons. With the larger vials or tubes, make a starter of about 1.5 liters, which also can be stepped up again if necessary.

By the way, a cup of DME in 750 ml of water produces a high O.G. (about 1.080) that can be stressful on the yeast. The general rule of thumb for yeast starters is to use a little more than one-third cup DME per 500 ml for an O.G. of about 1.040.
 

BrewMonkey (152.163.252.67)
Posted on Tuesday, December 16, 2003 - 07:24 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Thanks Bill, Actually I wrote it wrong, I add 1/2 cup of DME to 750 ml of water. I usually let the starter ferment out, put it in the fridge for a few days to settle the yeast out, pour the liquid off the yeast then pitch the slurry only. Have you found this to be a good way or should I be pitching the full starter while it's fermenting.
 

Bill Pierce (24.141.63.119)
Posted on Tuesday, December 16, 2003 - 07:49 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

There is a long debate about whether to pitch mostly the yeast sediment or to pitch the entire starter when it is at full kraeusen. Frankly I don't believe it makes a lot of difference as long as the starter isn't terribly different in composition from the style you are brewing and the yeast itself is relatively fresh and healthy. If the starter is different from your beer, then go ahead and crash it and pitch mostly the sediment.
 

Ken Anderson (24.55.255.75)
Posted on Tuesday, December 16, 2003 - 08:15 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

It's probably been explained before, but other than lessening the chance of contamination, why can't you just pitch to quantity and not worry about stepping up? I don't see how the volume of wort that a yeast population is introduced to can affect its growth rate.
 

Denny Conn (63.114.138.2)
Posted on Tuesday, December 16, 2003 - 08:26 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Ken, in a nutshell, if that worked we wouldn't need starters. Just pitch a single grain of yeast into a 5 gal. batch and you'd be set! :)
 

Ken Anderson (24.55.255.75)
Posted on Tuesday, December 16, 2003 - 09:51 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I don't know! There are concerns about the amount of yeast reproduction that takes place in fermenting beer. I understand either extreme is not a good thing, ie, under or over-pitching, speaking just in terms of flavor contributions. Also, with several gallons of wort, you do want a quick onset to fermentation because of sanitation issues. At least this is the way I've understood it.
 

chumley (199.92.192.126)
Posted on Tuesday, December 16, 2003 - 10:20 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

What would be good is to brew up a large batch, say 40 gallons, of 1.050 beer, split it into 8 five gallon batches, and add different amounts of the same yeast, ferment at the same temperatures, and see what you get in terms of (1) flavor; and (2) attenuation. Say 0.125, 0.25, 0.5, 1, 2, 4, 8, and 16 oz. of slurry added to each, giving them the same blast of O2.

Where oh where would we ever find a homebrewer capable of brewing 40 gallon batches of beer? :)
 

Bill Pierce (24.141.63.119)
Posted on Tuesday, December 16, 2003 - 10:29 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

The purpose of making a yeast starter is to propagate yeast. The purpose of pitching yeast is to ferment beer. Obviously these are related but they are not the same thing. There is a limit to the number of times the yeast can reproduce without undue stress that would have a negative effect on the fermentation and flavor. The 8-10 times increase in the population represents a reasonable compromise. I have been told that under actual fermentation conditions it can vary from three to 20 times.
 

Fredrik (213.114.44.219)
Posted on Monday, December 22, 2003 - 07:24 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I finally got back for Xmas from another week of work in Austria. I got a nice original Edelweiss beer glass :)

To the original question I would suspect many small steps will generally give more yeast put it simple. I speculate that the mainreason is a higher oxygen utilization for growth limiting compounds.

I understand Ken's thinking though, at first thought it seems that 1000 ml of 8ppm O2 wort contains as much oxygen as 2x500 ml of 8ppm O2 wort, so this shouldn't be the issue. But I think the amount of oxygen that is used for synthesising *growth limiting compounds* are proportional to the amount of initial yeast and this happens during the first hours. So in a very big volume, a smaller % of the total oxygen is used for the critical processes. The bulk of the O2 is used, but probably for things that doens't improve growth. So making two steps, effectively means saving 50% of the total oxygen for mid fermentation of the starter. This will give better essential oxygen utilization that just a big O2 boost in the start.

100% of the oxygen is always depleted from wort. The question is how big part of this is used to promote growth, and what about the other part?

/Fredrik
 

Jeremy S (205.188.208.75)
Posted on Monday, December 22, 2003 - 09:49 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Fredrik-I can always count on you to give me a headache...don't get me wrong, I admire your scientific insites into the wonderful world of beer and yeast...but would it hurt you just once to buy the stuff for a batch, brew it, pitch your yeast, wait a week and rack, secondary condition and bottle and enjoy? And do it all without your trusty microscope? Just so ya know...I'm just funnin' ya! :)

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