Hi guys. A few days ago I have been advised to do not cold crash beer for a long period( 2 months) due oxidation risk(low risk). Well I am reporting back what has happened with one of the two batches I have in this condition. I racked it to a keg yesterday and force carbed before bottling observing a crystal clear beer wich tastes very good without any trace of stalling, this fermentor had a little(1/3gal) headspace though. I have another one with a 3/4gal headspace that I will be bottling this weekend. I will report it back as well.
I think the point here is applied to when people cold crash with an airlock. What happens is, as the beer cools it not only absorbs the gas in the head space but that air in the head space also contracts and becomes more dense; thus a relative vacuum is created and outside air is sucked back into the fermentor introducing oxygen into the beer. An S-shaped airlock will allow "suck-back" without losing fluid, whereas, the three piece airlocks will dump the fluid into the fermentor. I personally learned this the hard way with a barleywine that turned to wet cardboard after three months in the keg. That batch was cold crashed in a carboy with an S-shaped airlock and then close transferred to a keg. The next time I brewed that batch, I closed transferred first to a keg then cold crashed. Lo and behold, zero oxidation in that batch and every batch since. Edit: you can also see this happen with a blow-off tube. As the beer cools liquid from the container will travel up the tube towards the fermentor.
What I do is take a sterile nitrile glove. Keep the 1 piece airlock on. Put the glove over the airlock, wrap the wrist end of the glove with electrical tape to seal it to the mouth of the carboy. Cut the end off a finger, insert tube that's been sterilized and flushed with co2. Fill the glove slightly with co2 and deflate to flush, then fill it to the point where it's ready to pop and tie off the finger. Now you can cold crash with no o2 introduced. For hoppy IPA's I take it a step further and totally flush the keg, then use a closed transfer with co2.
If you willingly introduce o2 into the beer and can't taste anything wrong, then I suppose it doesn't matter. Generally, it's a good practice to prevent post fermentation o2 exposure and especially o2 absorption whenever possible. I used to cold crash my beer until I realized it wasn't necessary or even beneficial. Flavor and aroma stability improved with hoppy beers without a fermenter cold crash. Cold storage in bottles or kegs clears the beer just as well.
Reporting back the second batch . I have bottled this second batch yesterday, I think I can taste a tiny bite of oxidation , maybe I am wrong , I can not define it precisely.Maybe it is part of the yeast profile , Coopers ale yeast produces some wooden flavor so it is possible I am making a mistake with my perception. I am not sure , I guess if it was oxidation bitterness shouldn´t be so smooth as it is right now, this beer has been dry-hopped 10 days using 1 oz EKG hops. I think I have overcarbed it , it was a real mess to bottle it, I haven´t had enough time to cap the bottle before it gushed so hard leaving a long headspace in each bottle, no matter how much counterpressure I used bottles always gushed. Whilst keg temperature was slowly raising it was getting worse so I stopped bottling , 2 gals remains in keg for tap dispensing. I think I will need to drink these bottles in a short term. Well ,I hope my experience could be useful for you. cheers !!
