- Apr 2, 2011
- Reaction score
- Arlington (DC)
This.It’s a good question and often the first one people ask when they start to contemplate why anyone would want to reduce oxygen exposure on the hot side when they are just going to aerate the wort before pitching.
The important thing to understand is that heat increases the kinetic energy of molecules therefore chemical reactions happen faster at higher temperatures. This means that the same staling reactions that take minutes in the mash will be slowed down to hours or days after chilling in the fermenter. Healthy yeast are quite capable of mopping up all available DO in less than an hour providing the protection to save your wonderful fresh malt/hop flavors and aromas.
Even at fermentation temps oxygen uptake, and the initial series of oxidation reactions, is quick (you measure DO in a brite tank during/immediately after a transfer vs the next day you'll see a noticeable difference), but yeast are quicker. If the assertion of the rate of oxidation to temperature as logarithmic is assumed to be true (which the chemistry suggests, and sensory for cold storage vs room temp vs hot storage of finished beer also validates), mash sparge and boil temp oxidation rates are orders of magnitude higher than fermentation temps.