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Old 12-13-2006, 10:39 PM   #11
boo boo
Jun 2005
Hearts's Delight, Newfoundland
Posts: 4,165
Liked 36 Times on 31 Posts

Doing a diacetyl rest usually depends on the strain of yeast used such as WY2308 but don't hurt to do for any lager since most of the fermentation is done by the time you bring up the temps to do the rest.

I think pitching an good starter at slightly below fermenting temps into wort at fermenting temps reduces the esters and fusels you'll get by pitching into warmer than recommended lager fermenting temperture wort.

I tried a recipie I brewed a while back using higher fermenting temps and got a good beer, but not a crisp lager.
How do you BBQ an elephant....first you get your elephant....

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Old 12-13-2006, 11:40 PM   #12
Dr Malt
Aug 2005
Pacific Northwest
Posts: 305
Liked 16 Times on 14 Posts

Thanks Dantodd for the explanation. If you would like a little more information on diacetyl, you might go to

The temperature will have an effect on the rate of metabolism of the yeast and thus the rate of diacetyl formation, but fermenting at cooler temperatures will not inhibit the formation of diacetyl. Lager yeast will still make plenty of diacetyl at their optimum fermentation temperatures (50 -55 F). So, even if you start your fermentation at say 50 F, the fermenting beer will have high diacetyl levels during primary fermentation. Once the yeast have utilized most of the mono, di, and triose sugars, they will begin metabolizing the diacetyl and thus reducing the levels. Breweries do a diacetyl rest (warm the fermentation for a short time) to speed the assimilation of the diacetyl by the yeast so they can package and sell the beer sooner. If you are not in a hurry, you can let the beer sit at fermentation temperatures (50 -55 F) longer and the yeast will continue to lower the diacetyl levels below flavor threshold. Because diacetyl will be made in abundance anyway during primary fermentation, I am not convinced DiegoPro needs to go to great lengths to cool his wort to 55 F initially because of diacetyl. If he gets it to say 70 F, pitches his yeast and then places it at 55 F, he should not have a problem with diacetyl if he either ferments for sufficinet time or does a diacetyl rest.


Dr Malt

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Old 12-14-2006, 07:14 PM   #13
Oct 2006
Posts: 17

Originally Posted by Dr Malt
Thanks Dantodd for the explanation. If you would like a little more information on diacetyl, you might go to
Thanks for the info! The link you supplied, though, seems broke. I found the article on my own though (you were missing an 's' in 'backissues'). Thanks for the reference. Here it is for everyone else:

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