Coating plastic carboys to prevent oxygen transfer?

[mrspock]

Recent batches have been going vinegary, despite diligent sanitation and watching my waterlock.

I've read that plastic carboys can transfer oxygen, and finally realized that this is what's probably happening in my case: Once fermentation is done, and positive pressure becomes neutral pressure, oxygen is free to diffuse into the batch, making it aceobacter partytime.

I'd prefer not to switch to glass, and am wondering if there's a way to prevent this. What about coating my carboys in vegetable oil?

Note: Substance being brewed is mead, which I tend to leave unattended for months on end. I'm guessing the plastic, probably better suited to shorter term batches.


Any help appreciated.
mrspock

 

[EJay]

Recent batches have been going vinegary, despite diligent sanitation and watching my waterlock.

I've read that plastic carboys can transfer oxygen, and finally realized that this is what's probably happening in my case: Once fermentation is done, and positive pressure becomes neutral pressure, oxygen is free to diffuse into the batch, making it aceobacter partytime.

I'd prefer not to switch to glass, and am wondering if there's a way to prevent this. What about coating my carboys in vegetable oil?

Note: Substance being brewed is mead, which I tend to leave unattended for months on end. I'm guessing the plastic, probably better suited to shorter term batches.


Any help appreciated.
mrspock

I don't think its like gore-tex porous. I think oxygen permeability is more of a theoretic thing that over time could cause tiny amounts of oxygen in which would oxidize the wine. Note that wine makers age in wood barrels in part because of the desired controlled oxidation that occurs, and others mimic it with microoxygenation. If that automatically led to acetebacter, all fermentation and aging would be done in stainless steel. I certainly don't think that is your issue. I don't know much about mead but I know a lot of commercial production of wine.

I'd be interested if you did the same batch in glass if it would be any different.

Respectfully, I suspect vegetable oil is at least as oxygen-permeable as PET, so I think thats a non-starter.

 

[Bensiff]

Most every home brewer has brewed very succesfully with plastic buckets, so when you have acetobacter the issue is more sanitation as acetobacter has to be present for the high level of oxygen transfer from plastic buckets to have an impact. Time to replace that bucket and your transfer lines or you will keep introducting the bacteria into your mead. As well, you are transferring oxygen the whole time, I can't remember the name of the principle, but it doesn't just occur when fermentation is done. Finally, whatever you do, do not put oil into your mead, beer, wine, or whatever. So, if you don't want glass and also don't want the permeability of plastic buckets (I wouldn't either for extended aging) get yourself a PET plastic carboy, such as a Better Bottle, its plastic and has almost zero oxygen permeability.

 

[Bensiff]

Respectfully, I suspect vegetable oil is at least as oxygen-permeable as PET, so I think thats a non-starter.

The PET they use for things like Better Bottles has virtually no oxygen permeability. The plastic buckets have relatively very high permeability.

 

[mrspock]

Thanks for the replies, all.

I should add that the plastic carboys are 25 years old.... so this may not be the same materials you currently know and love.

I've sanitized the bejesus out of things, and am comfortable ruling that out.

I used the bottle my mead quite green... but I realized that once I started letting it sit in the carboys longer is when I had troubles.... Thus I attribute issues to time/diffusion.

Great tip on PET carboys... I'm going to go buy one. Probably better than the old school stuff I'm using.

Thank you.

 

[flars]

What is your sanitizer and what is the sanitation regime you use?

 

[kh54s10]

I would be leery of 2 things. 1) 25 year old plastic 2) 25 years of bad things growing in the plastic.

It is relatively common advice that when you have issues with plastic - replace it.

My guess is that if you get new PET fermenters your problem will go away. I have left beers in primary for over 3 months and they have turned out very good.

 

[mrspock]

What is your sanitizer and what is the sanitation regime you use?

Good question.

First, I rinse used carboys to get the sediment out, and clean with a bottle brush. Then I fill with water, and add a few tablespoons of the pink chlorine cleaner, and let sit for a few weeks. Then I bottle brush again, give it a few rinses and a few shakes, and back into operation.

Tubes, etc, are similarly cleaned.

 

[helibrewer]

Replace the old carboys. I age wine in Better Bottles for about a year before bottling and have never had an infection. I also ferment beer in them...again no issues.

Switch from chlorine and clean with something like OxiClean and then sanitize, StarSan is a good choice. Chorline plus anything phenolic is going to give you off flavors.

 

[flars]

What you are using is Diversol. Sold also as The Pink Stuff, Sani-brew, Stericlean, Sparklebrite, and other names. It is chlorine based. Needs a long contact time to sanitize. Works very well as a cleaner. It requires heavy rinsing with hot water.

Once you rinse with hot water surfaces are no longer protected and can harbor bacteria or wild yeast from that point on. I use PBW for a cleaner now, but Diversol could be a substitute if it didn't contain bleach. I stay away from bleach now.

Using brushes on your plastic can leave scratches, which in turn can harbor infectious materials.

I would suggest changing out your old plastic for new and switching to Starsan for a sanitizer. Starsan is no rinse, effective on surfaces which remain wet with the solution.