Author Topic: My first yeast starter - questions!  (Read 9491 times)

Offline maxieboy

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Re: My first yeast starter - questions!
« Reply #15 on: February 13, 2011, 09:08:19 PM »
  Storing it in the fridge will cause a longer lag time when you pitch it into the wort. 

Could you expand on this? Myself and lots of excellent homebrewers have followed numerous commercial breweries lead of pitching cold.
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Offline a10t2

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Re: My first yeast starter - questions!
« Reply #16 on: February 13, 2011, 09:28:37 PM »
1 cup DME = 1cup x 8oz/cup x 29.57mL/oz x 1.6g/mL = 378.5g DME

Obviously there's a lot of variability, but a cup of DME is ~150 g.
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Offline tygo

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Re: My first yeast starter - questions!
« Reply #17 on: February 13, 2011, 09:45:06 PM »
If it were me, I would make a new yeast starter from scratch, using 100g of DME to 1 liter of water

Good advice  ;)

If you should decide to use what you have, storing it in a dark, room-temperature place for a day or two is good.  Storing it in the fridge will cause a longer lag time when you pitch it into the wort.  For more than a day or two - the fridge is the way to go.

I always chill my starters down in the fridge.  I haven't had any problems with lag time thus far.
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Offline maxieboy

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Re: My first yeast starter - questions!
« Reply #18 on: February 13, 2011, 09:45:43 PM »
1 cup DME = 1cup x 8oz/cup x 29.57mL/oz x 1.6g/mL = 378.5g DME

Obviously there's a lot of variability, but a cup of DME is ~150 g.

It appears that it's just not his day... ;)
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Offline maxieboy

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Re: My first yeast starter - questions!
« Reply #19 on: February 13, 2011, 09:49:03 PM »
I always chill my starters down in the fridge.  I haven't had any problems with lag time thus far.

+1
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Offline punatic

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Re: My first yeast starter - questions!
« Reply #20 on: February 13, 2011, 10:04:31 PM »
1 cup DME = 1cup x 8oz/cup x 29.57mL/oz x 1.6g/mL = 378.5g DME

Obviously there's a lot of variability, but a cup of DME is ~150 g.

It appears that it's just not his day... ;)

Hey you guys liked the 1.6g/mL for DME  figure just fine when I used it here:
How Do you Make a Yeast Starter?

Also, 1 cup of water weighs 236.7g 
1cup x 8oz/cup x 29.57mL/oz x 1g/mL = 236.7g

So you're saying your cup of DME only weighs 2/3 as much as cup of water?
If I were you I'd take that DME back to the store and get a refund.   ::)
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Offline maxieboy

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Re: My first yeast starter - questions!
« Reply #21 on: February 13, 2011, 10:43:56 PM »
 A cup of DME does not weigh 378.5g(13.35oz!). You won't convince anyone of that. Depending on brand and how you measure a cup, 4.5oz-6.5oz at the most.
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Offline morticaixavier

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Re: My first yeast starter - questions!
« Reply #22 on: February 13, 2011, 11:32:39 PM »
1 cup DME = 1cup x 8oz/cup x 29.57mL/oz x 1.6g/mL = 378.5g DME

Obviously there's a lot of variability, but a cup of DME is ~150 g.

It appears that it's just not his day... ;)

Hey you guys liked the 1.6g/mL for DME  figure just fine when I used it here:
How Do you Make a Yeast Starter?

Also, 1 cup of water weighs 236.7g 
1cup x 8oz/cup x 29.57mL/oz x 1g/mL = 236.7g

So you're saying your cup of DME only weighs 2/3 as much as cup of water?
If I were you I'd take that DME back to the store and get a refund.   ::)


Are you thinking of LME? Liquid Malt Extract? Dry malt extract is very light compared to water. as not particularly easy to measure by volume (fl oz) as the amount of moisture in the air will greatly affect the weight as will how tightly packed the cup is.

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Re: My first yeast starter - questions!
« Reply #23 on: February 13, 2011, 11:34:57 PM »
DME has a density of 1.6 g/mL
1 cup = 8 fluid oz.
1 fluid ounce = 29.57 mL

1 cup DME = 1cup x 8oz/cup x 29.57mL/oz x 1.6g/mL = 378.5g DME  
Fair enough, but that cup of DME is not full of 100% DME, it has quite a bit of air.  A cup of DME measured from a bag of powdered DME will weigh about half of that.
Tom Schmidlin

Offline punatic

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Re: My first yeast starter - questions!
« Reply #24 on: February 14, 2011, 12:56:39 AM »
OK - rule of thumb 1 lb of DME added to 1 gallon of water will give you a specific gravity of 1.045

1 lb DME = 1 lb
1 gal water = 8.34 lb
1 lb DME + 1gal water = 9.34 lb

9.34 lb / Vwort = 1.045 x (8.34 lb/gallon)
9.34 lb/ Vwort = 8.715 lb/gallon
9.34lb / (8.715 lb/gallon) = Vwort = 1.072 gallon
Vdme = Vwort - Vwater
Vdme = 1.072 gallon - 1.000 gallon = 0.072 gallon
density of DME = 1 lb / 0.072 gallons = 13.89 lb/gallon
(13.89 lb/gallon) x (1 gallon / 16cup ) x (16 wt.oz / 1 lb) = 13.89 wt.oz. / cup
Specific Gravity of DME = (13.89 lb/gallon) / (8.34lb/gallon) = 1.665

Recall - Specific gravity can be expressed as g/mL 
therefore DME density = 1.665 g/mL
More dense than the 1.6 g/mL I used in my previous calculations
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Offline tygo

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Re: My first yeast starter - questions!
« Reply #25 on: February 14, 2011, 05:15:17 AM »
It's a little early in the morning for me to follow math.  But I can scoop a cup of DME out of the bag and put it on a scale.  185 grams.  Munton's Extra Light DME, full cup, packed down somewhat.
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Re: My first yeast starter - questions!
« Reply #26 on: February 14, 2011, 08:37:59 AM »
OK - rule of thumb 1 lb of DME added to 1 gallon of water will give you a specific gravity of 1.045

Actually, that isn't quite right either. One pound of DME made into a solution with a *total volume* of one gallon will have an SG of around 1.045. You're also assuming that the volume of the solution is equal to the sum of the volumes of the solute and solvent, which is a notoriously common fallacy in chemistry.

Using the density of a solid's constituent particles introduces a lot of error when that solid is granular. The packing fraction will make a huge difference. The variation between sifted and packed flour, for example, is 25%: http://www.cookingforengineers.com/article/63/Wheat-Flour That's why people are always encouraged to measure by mass rather than volume.

Notice that you're saying a gallon of DME weighs about 14 lb. I'm sure you've seen a 5 lb bag of DME at a LHBS or elsewhere. Does it have a volume of 1/3 gal, or is it more like a gallon?
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Offline punatic

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Re: My first yeast starter - questions!
« Reply #27 on: February 14, 2011, 09:10:51 AM »
Alright.!  Some of you are getting close.

A hint:
bulk density vs particle density...
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Offline denny

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Re: My first yeast starter - questions!
« Reply #28 on: February 14, 2011, 09:14:49 AM »
Storing it in the fridge will cause a longer lag time when you pitch it into the wort.

Certainly not in my experience.  I took a slurry out of the fridge yesterday and within 10 min. I pitched it, before it could warm up.  I had fermentation going within 2 hours.
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Offline maxieboy

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Re: My first yeast starter - questions!
« Reply #29 on: February 14, 2011, 09:34:10 AM »
Alright.!  Some of you are getting close.

A hint:
bulk density vs particle density...

 ::)
 I'm no mathmagician or scientist, but you don't need to be to figure out the DME volume and weight issue.
We're still waiting on the cold pitching lag time theory...
Macros, micros and brewpubs are doing it and they have the most to lose if something goes wrong due to increased lag times.
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