The mystery about the 30*C rule
Posted: Wed Oct 18, 2006 6:27 pm
I guess many of you have heard about this rule with regards to brewing German wheat beers: The pitching temp in deg Celsius + the fermentation temp in deg Celsius should equal 30 deg Celsius.
I know that the Doc was talking about that in one of the Dan Gordon shows and even the Dan didn't know about that. I also read about that rule in the Classic Beer series book about German wheat beer.
Now I seem to have found the explanation of that rule. It is a rule that stems from a time when fermentation vessel cooling was not common. By having a constant room temperature and choosing a low pitching temp it was possible to control the maximum temperature of the fermentation. Narziss writes in "Abriss der Bierbrauerei" (An Abstract of Beerbrewing) when writing about pitching of top fermenting beers (loosly translated from German):
"The pitching temp is between 12 and 16*C. It should be choosen such that, in conjunction with the two other factors aeration and pitching rate, a particular maximum temp will be reached and not exceded. If cooling of the fermentation rooms or vessels is available the pitching temp can be choosen more freely. In the olden days it was the rule that the sum of pitching and room temperature should be 30*C meaning that with a fermentation room temperature of 18*C a pitching temp of 12*C was chosen and vice versa"
What does this mean for the home brewer: If you can force the temp of your wheat fermentation to be the desired fermentation temp you don't really have to worry about your pitching temp. Keep it close to your fermentation temp. If you are fermenting in the basement with an ambient temp of 19*C (like me since I need my fride for lager fermentations) and you want to make sure that your max fermentation temp doesn't exceed a particular temp, you may want to pitch colder. But I'm not sure if the 30*C rule applies here since a 7 gal bucket heats up much faster to room temp than a 100 hl commercial fermetation vessel.
Kai
I know that the Doc was talking about that in one of the Dan Gordon shows and even the Dan didn't know about that. I also read about that rule in the Classic Beer series book about German wheat beer.
Now I seem to have found the explanation of that rule. It is a rule that stems from a time when fermentation vessel cooling was not common. By having a constant room temperature and choosing a low pitching temp it was possible to control the maximum temperature of the fermentation. Narziss writes in "Abriss der Bierbrauerei" (An Abstract of Beerbrewing) when writing about pitching of top fermenting beers (loosly translated from German):
"The pitching temp is between 12 and 16*C. It should be choosen such that, in conjunction with the two other factors aeration and pitching rate, a particular maximum temp will be reached and not exceded. If cooling of the fermentation rooms or vessels is available the pitching temp can be choosen more freely. In the olden days it was the rule that the sum of pitching and room temperature should be 30*C meaning that with a fermentation room temperature of 18*C a pitching temp of 12*C was chosen and vice versa"
What does this mean for the home brewer: If you can force the temp of your wheat fermentation to be the desired fermentation temp you don't really have to worry about your pitching temp. Keep it close to your fermentation temp. If you are fermenting in the basement with an ambient temp of 19*C (like me since I need my fride for lager fermentations) and you want to make sure that your max fermentation temp doesn't exceed a particular temp, you may want to pitch colder. But I'm not sure if the 30*C rule applies here since a 7 gal bucket heats up much faster to room temp than a 100 hl commercial fermetation vessel.
Kai
But we already know that this is something he doesn't know and that would be unfair even for "Stump The Brewer".