How long is safe to age in a plastic carboy w/ large headspace?

[The5thHerring]

So I have a traditional going, trying to age off a variety of stanky hot-fermentation aromae. I racked from primary to another carboy a few days ago.

It's one of those blue water-cooler jugs, and is filled only about 4/5. So a large headspace. Also, I don't have a completely airtight lock -- just a (non-airtight) plastic screw cap, with a party balloon sort of condom'd over the cap and neck.

I was wondering how long I could reasonably expect to age it in this environment without ruining it due to oxidation? I'll probably transfer to 4-5 glass gallon jugs next, fully airtight. (Don't have those jugs on hand yet.)

Also I should mention: I've opened the cap to smell it, so the CO2 "blanket" is compromised. It's not producing much (if any) anymore.

 

[Chevette Girl]

I think the last time I had to age something that wasn't making CO2 anymore in a container with lots of headspace, I added a little bit of sugar or honey to get it to make a bit more CO2... and I've aged for months in a plastic water jug with plastic wrap and a rubber band instead of an airlock, no problems I can see attributed to this treatment... you do what you can, and hope for the best.

 

[PitBull]

Reducing is a good idea.

Traditional meads are pretty resilient to oxidation. That being said, it’s probably a good idea to rack to smaller carboys to reduce headspace and not take any chances. I’ve always found it’s better to get jug wine at $12/gallon and empty them one glassful at a time than to pay $4 for an empty gallon.

Remember not to leave too little headspace. When your mead warms up, such as going from winter to spring to summer, the volume of mead can expand more than the volume of the carboy. The mead will then be forced through the airlock. This happened to me when I left only ¼” of headspace. I guess it could also happen when it the mead cools (in winter) if the carboy contracts more than the mead inside. The contraction case is probably less likely to be a problem, as I have not experienced it.

 

[Medsen Fey]

While traditional meads are fairly resistant to oxidation, it certainly is possible, and will create a sherry/nutty aroma that can actually be good, though it will be considered a major fault in a table mead/wine.

More worrisome is the potential for spoilage. If you keep a large headspace with oxygen in it, acetic acid bacteria and other spoilage organisms can have a field day, especially if there is residual sugar. Unless your ABV is above 17%, the alcohol won't stop them. Sulfites won't stop them either unless you use massive doses.

I'd suggest you get it into a full container or use some method such as outlined in this thread.

 

[Dan McFeeley]

This is from personal observation from accidents like popping carboy bungs -- some meads seem ok when exposed to O2 during the aging process, others have taken on a bitter taste. It seems to depend on the type of varietal honey/s used in the mead.

I've learned from experience and wire down all my carboy bungs. ;D

--

 

[The5thHerring]

Rereading all this, I think it would be prudent to seal off the top of my mead.

The most economical thing to do would probably be to pour some vegetable oil on top of the mead surface. I would leave it for only a month or two before racking to several smaller containers.

Such a timeframe seems like it should be pretty safe from rancidity. But if it does go rancid, will the flavor transfer into the mead?

 

[JamesP]

Once it has stopped giving off CO2, I don't trust that much air space more than a week, especially not if it is hot.

I try to check any plastic carboys I have aging every month and top-up to zero headspace (tight lid to avoid spillage from expansion/contraction).
It can go down by up to 0.25 of an inch every month or two. Much more head-space and it starts getting the cardboard taste being detectable in top portion of your mead.

Of course this is dependent on your mead, the temp/humidity, the plastic and the lid seal, etc, so YMMV

 

[The5thHerring]

Well, it had been two weeks and two days in the carboy with the extra gallon of headspace. I just poured on about 3/8 inch of vegetable oil.

It smelled a little sourer than a week ago -- not enough to worry me overmuch, since it's just another riff on this mead's menagerie of bad smells, but you can't be too careful... so, what if I shoved a Campden tablet or two down past the oil?

Would that be too soon? I don't want to kill off the yeast if it still has good work to do. But on the other hand, I would like to feel secure against acetobacteria. And wouldn't mind seeing it clear sooner.

 

[Chevette Girl]

I'm not sure how well campden tabs would get through the oil, but if you do try it, please post what happens , inquiring minds wanna know.

I suppose you don't have a hydrometer? That's the only way to know for sure if your yeasties still have work to do or not. Have you tasted it? If it's still sweet, there's still available sugar. If it's dry dry dry tasting, there's probably no sugar left but tongues are not particularly well calibrated for determining sugar content ;D

And I think acetobacter needs oxygen to do its thing so blanketed under oil, you're probably safe from any further activity if there was any to begin with.

 

[The5thHerring]

I do have a hydrometer. I took a reading right when I racked into secondary, and it was around 1010 or so. Bubbling/outgassing was still going on for a few days, then stopped, and I've seen no activity for the past two weeks.

I haven't taken any readings since then because my headspace is too big to reach the surface with my thief! And I don't want to mess with siphoning until I'm ready to rack again.

I remember reading on these forums that fermentation is about as hard to stop as a freight train, once it's going. So presumably Campdens won't wreck it if it has much further to go. I will mull this over and maybe put them in in a few days.

 

[Medsen Fey]

You don't need to worry about Campden tablets while it is under a blanket of oil. Acetic acid bacteria will not be working without air. And by the way, next time if you'll use mineral oil (baby oil) that is available in the pharmacy as a laxative, you can be sure it won't contain harmful contaminants and it won't ever go rancid.

 

[The5thHerring]

I figured it would be reasonably safe to go with vegetable oil this time, since it won't sit there for more than a month or two before I rack to gallon jugs. An acceptable risk for me.

Campdens at racking time, I suppose, to stabilize.

 

[The5thHerring]

So! in the last few days, there has been an accelerating amount of bubbling from up under the oil. (it had been almost completely still for the previous few weeks). Also, I think I have been smelling volatile acids being thrown off. To me, that means either...

a) My fermentation had been stuck, and it commenced again, but the yeast were stressed and decided to make acids before turning them into alcohol, or...

b) I introduced lactic or acetic bacteria with the vegetable oil, and they were taking off.

The latter seemed more likely, since I was only at 1.013 or so at racking time. Not much distance left to go. So I sulfite bombed it. Tossed 6 Campdens (really chucked 'em in, so they would go through the oil layer) and away they fizzed.

That was this morning. Now there is no bubbling, although a bunch are trapped in the oil now. Should I expect the mead to start clearing, now that I've gone and sulfited it?

 

[Medsen Fey]

So it smelled like nail polish?
Under a layer of oil, acetic acid bacteria will not be able to function, and lactic acid bacteria are unlikely in a traditional mead. It is probably your heat-stressed yeast just doing their thing.

 

[The5thHerring]

It started to smell sharpish, almost like vinegar. Not "chemical" like nail polish really.

At any rate, if the yeast were indeed going strong again, they might well survive the bombing. (Since I didn't sorbate it alongside). Time will tell.

This was a move more for my peace of mind than anything.