Conical Fermenting - Sanitary Practice

[DanMax]

I have a Blichmann conical fermentor. I keep the temperature constant in an upright temperature controlled freezer. I use a blow-off tube to dissipate the CO2 during the fermenting process. I lower the temperature to crash the fermenting process. This lowers the pressure within the fermentor vessel. When I open the valve to remove the trub yeast from the bottom of the fermentor, air is sucked into the fermentor which may oxidize or contaminate the beer. Air is also sucked in when I take a sample from the fermentor to measure the specific gravity.  What can I do to alleviate the problem? Can the air being sucked into the fermentor spoil the beer?

[KellerBrauer]

Greetings DanMax - while I agree with the assertion that air (oxygen) will cause beer to spoil and cause off flavors, I believe too much is read into the subject.  We all have to syphen, or rack, our beer into another vessel - typically a bottling bucket - and air inevitably enters the fermenter while doing so unless it's done under a CO2 blanket.  Further, some brewers - like me - bottle their beer which also introduces air to beer (unless one uses one of the new gadgets that puts the beer into the bottle while under a CO2 blanket).

I read an article not long ago where a guy stuffed cotton in his air lock so it could act as a filter when the fermenter is opened/drained.

Personally, I don't believe your practice will cause any noticeable affects in your beer.  I'm certain other brewers will have a different opinion.  But my opinion is the little contact air makes to my beer, following a similar practice as yours, is negligible.