Sat Oct 16, 2010 5:12 am
Crabtree effect kicks in at about 0.1-0.4 % glucose (depending on which text book you are reading) And basically every single wort has waaaaay more glucose than that.
That's the point.... Aerobic respiration, to all intents and purposes, just doesn't happen in a beer fermentation. There is either so much glucose around that it's repressed via crabtree, or by the time wort glucose levels have dropped to the point where there is less than 0.1% - there isn't any oxygen left to respire with.
The standard "dogma" of how a fermentation proceeds, is nothing more than a simplified and somewhat inaccurate model. Follow the model's logic and in most cases the resulting action will be the best one.... But if the object of the game isn't just to take the right action, but to actually understand at a deeper level what's going on... Then it stops being useful.
The reason I think it needed exploring in this thread, was because when people start talking about not needing to aerate your wort when you use dry yeast... That's one of the times when the standard model's logic starts to look a little patchy and people get confused. If people care enough to ask the question in the first place, perhaps they might also care enough, god help them, to wade through the slightly less simplistic and hopefully less inaccurate poppycock that we have been spouting in this thread.... And maybe they'll find something that helps them understand what's going on a little better - or at least make them glad that they don't care.
