A simple way to make plastic PET bottles as oxygen-proof as glass (almost!)

[sammy7boy]

Quick introduction: i'm a first time cider maker with limited prior homebrewing experience. I've made plenty of mistakes but learnt loads of things during my current cider project.

One of my many mistakes was to inocculate my rather acidic cider with a commerical malolactic strain of bacteria, then bottle it a few days later rather than allow it time for a malolactic fermentation. No sweat, i thought, i use PET bottles anyway which means i can easily release excess CO2 caused by the malolactic fermentation. That was before i read this enlightening article by Andrew Lea http://www.cider.org.uk/bottles.htm

SO ... i learnt ... glass is way superior to plastic because it is totally impermeable to oxygen, unlike PET. How was i going to make my plastic bottles impermeable to oxygen to guarantee a quality oxygen free finished product and a nice anaerobic fermentation? I spent days pondering over this. In the end i realised that the easiest, simplest, cheapest solution would be to foil-wrap my bottles in self-adhesive aluminium foil tape. Was really easy and cost next to nothing. Aluminium, like glass, is almost totally impermeable to oxygen. Yes ok there is still some naked PET but i reckon 80% or so of the surface area is covered. I'm not brewing for commercial purposes so it doesn't matter to me that my bottles look like they've been created for consumption on the International Space Station...

Thought this was an idea worth sharing on this forum!

 

[SerifSansSerif]

Unfortunately.... That idea doesn't strike me as doing much of anything...

It's still contained in plastic, and the adhesive is even more air permeable, and the foil won't hold a damned thing.

Plastic is fine. Glass is better, but not by THAT much, especially if you're not aging or storing for long periods of time.

If you want to improve the storage you got, the best thing is to by darkly colored bottles to keep the light damage to a minimum. I'd say the foil idea might help with that, but honestly, you aren't covering it all up anyhow.

Really, just get glass beer bottles. They're $14 (or less) for 24.

 

[MarkKF]

Really, just get glass beer bottles. They're $14 (or less) for 24.

Or only 5 cents each when you buy beer, too

 

[gregbathurst]

You need to do a comparison of PET, PET + foil and glass. I know that the problems with PET become apparent after a few months so it should be easy to judge if the foil works. Still, I can't see it catching on.
I use 200L plastic bags for storing my cider before bottling, they have a foil "metallised" barrier layer to keep oxygen out, works quite well.

 

[MaxStout]

I don't see an advantage to doing this for reducing O2 permeation. I think the O2 will pass under the foil, through the adhesive layer. I'd have to see some empirical data from controlled experiments to be convinced otherwise.

I do see one benefit to your plan: The foil will protect the beer from light.

 

[SerifSansSerif]

Or only 5 cents each when you buy beer, too

Either way, still far cheaper than the cobalt blue wine bottles I liked to buy when I first started... (and the same bottles everyone like to keep )

I learned my lesson and just get the cheap bottles for regular stuff, and save what I got left of those for something special.

I'm sure you could also be resourceful and just collect them from your neighbor's bins on recycling day as well. A run through the dishwasher and a check for any cracks or chips is probably all they need.

 

[sammy7boy]

Thanks for all the responses! Yes glass would have been better but i realised this after bottling - and i'd have probably oxygenated them way more by pouring them all into glass bottles afterwards!

I have to disagree that the foil "won't do anything". Yes some oxygen will pass under the adhesive, but since we're dealing with the science of partial pressure we need to be talking in the language of the surface area available to the oxygen to this. The surface area available for oxygen to enter the adhesive is miniscule compared to the area covered by foil. I confident that this approach will give about an 85% reduction in the oxygen transfer through the PET. I'm no expert to homebrewing but i do have a physics degree and i'm a science teacher by trade!

Looking forward to tasting the results