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Old 12-05-2010, 04:23 AM   #1
thrstyunderwater
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I understand that really high temps can kill yeast, but if you're going to ferment at say 65 why can't you pitch yeast while the worts still at 100? That's not hot enough to kill it and it'll be cooled down to 65 soon enough.

 
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Old 12-05-2010, 04:37 AM   #2
ChshreCat
 
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The warmer the environment, the more active the yeast will be. If you pitch warm, the yeast will get going quicker. Fermentation is an exothermic reaction, meaning it generates it's own heat. So, if you pitch too warm the yeast can take off quick and it can be hard to get it down to fermentation temps before they start spewing out off flavors and fusel alcohols.

 
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Old 12-05-2010, 04:47 AM   #3
thrstyunderwater
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Quote:
Originally Posted by ChshreCat View Post
The warmer the environment, the more active the yeast will be. If you pitch warm, the yeast will get going quicker. Fermentation is an exothermic reaction, meaning it generates it's own heat. So, if you pitch too warm the yeast can take off quick and it can be hard to get it down to fermentation temps before they start spewing out off flavors and fusel alcohols.
I thought it took ~24 hours for yeast to show signs of activity? Wouldn't it also take less than a few hours for 5 gallons to drop 20-30 degrees? Is that enough time to spew out off flavors?

 
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Old 12-05-2010, 06:24 AM   #4
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It can be. I've had them take off in just a few hours.

 
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Old 12-05-2010, 06:30 AM   #5
rockfish42
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Yes, many of the off flavors are produced during yeast reproduction which occurs before visible signs of fermentation.

 
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Old 12-05-2010, 07:36 AM   #6
Waunabeer
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Trust me, my first 3 brews tasted like crap mostly due to high wort temps when pitching the yeast. Tasted like a weak bodied beer with isopropyl alcohol added to it. They sucked
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