Secondary fermentation: "cubitainer?"

[sentfromspain]

So I'm looking to get some more professional supplies, and I've been eyeballing these "cubitainers" and "Bags in a box"

The cubitainers would be a benefit, because I could:
-brew a batch
-leave it in the primary fermenting container for 10/14 days
-siphon out the brew into the second fermentation containers and leave the primary fermenting container free for the next batch that I would brew the day after.

And a further benefit would be that since they are made of a semi-rigid plastic, I could do half batches for recipe experiments (this way I save on supplies) and push out the air (to an extent).

My questions are:
-Has anyone tried out cubitainers?
-Would the cubitainers or bags in a box need air locks?
-As I generally leave my brews in the primary containers until bottling, I don't know how important it is to make sure that a secondary fermenting container doesn't have any air in it. Would I have to push out ALL of the air from the container?

 

[GodsStepBrother]

I sometimes ferment my experimental batches in these little rectangular things.

It works perfect, but I have never used a cubitainer or a bag in a box. I do not see what the problem would be though as long as it was the correct plastic.

 

[sentfromspain]

But if that is the case, why do they tell you not to let air in the second fermenting container? I mean, if you can leave the beer in the primary - and there is air in there, why would air being in the secondary fermenter be a problem?

 

[GodsStepBrother]

This is the primary you are looking at. Primary fermenation is fine with air space because yeast is producing a lot of co2 that is pushing out all the 'air' in the headspace. Once you are done fermenting then it is time to get rid of that headspace, because there is no longer a blanket of co2 protecting the beer from oxygenation. Though this is debated, especially if you do not move the beer around a blanket of co2 will reside on top of the beer protecting it, but then again why chance it.

Here is the same beer in secondary, I usually never secondary but in this instance i did b/c of the headspace.

 

[pickles]

But if that is the case, why do they tell you not to let air in the second fermenting container? I mean, if you can leave the beer in the primary - and there is air in there, why would air being in the secondary fermenter be a problem?

In the primary vessel fermentation has produced CO2 and has pushed out the "air". The CO2 is more dense than the "air" so it stays in the container. If you transfer to a secondary it's a good idea to blanket the headspace with CO2 to prevent oxidation since fermentation is most likely finished.

 

[GodsStepBrother]

pickles, I have a question about this. Isn't there a lot of co2 in solution in the beer when we are moving to secondary? Wouldn't the transfer alone provide enough movement to bring out some co2 out of solution and give it a nice natural blanket? I always feel weird peppering the beer in a fermenter with co2 from a tank.

 

[sentfromspain]

Yeah that's I thought too. There should be some dissolved co2 in the brew already, so if I made sure to push out all the air after filling up the "cubitainer" or "bag in a box," and place an airlock on it, then there probably wouldn't be much risk for oxidation... right?

 

[GodsStepBrother]

Well I have never suffered ill effect from doing this, but then again we are brewers and like to nit pick to avoid any risk