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Too Long on a Stir Plate?

http://thebrewingnetwork.com/forum/viewtopic.php?f=19&t=22344

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Too Long on a Stir Plate?

Posted: Sat Oct 02, 2010 4:23 pm
by TheDarkSide
I have a starter cranking away right now on s stir plate for about 24 hours. I am brewing tomorrow and not sure if I want to crash it in the fridge or just let it run on the stir plate. I will probably be pitched at about 40 hours if I leave it.

The yeast strain is WLP002. Is this too long on a stir plate? It's looking pretty chunky right now. The beer is going to be Lagunitas Brown Shugga clone,at 1.099 SG.

Thanks.

P.S. I just got the new yeast book today...too bad they spelled Justin's name wrong in the forward ( Crossly ).

Re: Too Long on a Stir Plate?

Posted: Sat Oct 02, 2010 7:59 pm
by Charlie
002 is a chunky yeast. It will make a cloud for the first 10-12 hrs, and then go snow globe on you. That's perfectly normal for a high-floc yeast.

For a stirred starter: If you pitch the whole thing do it at peak krausen (+18 hrs after innoculation). If you crash and decant let it go +24 hrs and crash. After 24 hrs your yeast will begin to enter rest phase, but even if you crash and decant they will get frisky pretty quick.

Disclaimer: I don't have any experience with non-stirred starters.

Charlie

Re: Too Long on a Stir Plate?

Posted: Sun Oct 03, 2010 6:45 pm
by tylercipriani
Most of the growth that you'll get out of a starter will be done (typically) in 24hrs.

I'd be wary about letting a starter go for 40 hours on a stir plate and then pitching the entire volume. Stirring a starter for that long may result in compounds in that starter that may carry over to the final beer. Oxidation of ethyl alcohol result in acetaldehyde since alcohol production is a reduction process. Futhermore, diacetyl is formed via oxidation.

Anecdotally, I was playing with a starter (doing sedimented volumes and whatever else) and I had it on the stir plate for 36hrs, then I moved it to the fridge (for some reason I can't recall) and then put it back on the stir plate a few days later and after 8hrs it reeked of diacetyl.

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