Carbonating in PET

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taylorjed1991

Carbonating in PET

Post by taylorjed1991 » Mon Jul 10, 2017 4:32 pm

Hi guys,

New to this forum but was hoping I could get some help understanding a little more about carbonating drinks in PET containers.

I currently brew in 5L metal mini kegs using a pressure release valve which I then put into the fridge to naturally carbonate however, when I do the same brew in a PET container the results don't seem to be as good.

I know the CO2 barrier properties of PET aren't as great as metal but are there any other attributes of PET which make it not as good to carbonate in?

And if the barrier is the only thing, do you have any suggestions to offset or fix the problem?

Cheers,

Jed

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Re: Carbonating in PET

Post by jaroporter » Mon Jul 10, 2017 6:10 pm

welcome to jims, jed!

afraid you're gonna have to give us more to go on than that. many people here use pet bottles with no problems, and it doesn't stop softdrinks manufacturers either. can you explain your process when packaging in pet vs minikegs?

and "not as good" in what way?
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Re: Carbonating in PET

Post by Fil » Mon Jul 10, 2017 10:13 pm

Well pet will contain much higher pressures so will be suitable for containing higher conditioned brews than minikegs. they are also a tad more elastic so if opened while under high pressure may contract a tad and can in some circumstances disturb more sediment, however chilling to the correct serving temp so the co2 is contained in the cool beer and not resulting in excess pressure..

if not priming fully perhaps leave the pet bottles in the warm a week or two longer, the only reason can think of for pet contained beer primed with a similar charge to beer in a mini keg other than it conditioning in the mini-keg a tad quicker as the metal keg normalises the temp to ambient a bit better??

the permeability of the plastic has more to do with o2 ingress than co2 escape, while im no chemist and am just repeating what ive read without quoting sources, but afaik co2 is a bit bigger than o2, but even o2 will struggle to force its way into a bottle that contains a positive pressure..

edit just read you condition in the fridge??? if so your yeast will need to be comfortable at that temp too so your restricting yourself to a small set of lager yeasts conditioning is best done in the warm at the same sort of temp as the primary fermentation in the brewbucket ;) in fact you can be less precouse about conditioning temps and let it go above the level you would be happy wh the main brew fermenting.. the fridge is the WRONG place 95% of the time..
ist update for months n months..
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Re: Carbonating in PET

Post by Wonkydonkey » Mon Jul 10, 2017 10:41 pm

Pet bottles are a good way to force carb with a carb cap.

But like Fil says the bottle contracts upon opening, and more co2 wants to escape. Etc.. But it's like most things you have to understand the pros and cons. Which is serve slightly colder beer and let it warm a bit before drinking.
Or drink 1/2 cold and 1/2 warm ...but really if there's sediment, serving colder means less co2 escaping, pour and let it warm a bit
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taylorjed1991

Re: Carbonating in PET

Post by taylorjed1991 » Tue Jul 11, 2017 9:35 am

Thanks for all the great replies.

Yeah I should have elaborated a little more, essentially what I've been doing has been using a carb cap to bring the vessel up to around 1.4 Bar then putting it in the fridge to allow the CO2 to dissolve/absorb into the brew; at least that's what I think happens.

Even though my process doesn't give the most amazing results I'm trying to figure out why the material change would affect it. And, Fli, like you said it might have something to do with the temperature normalising.

Again, cheers for the help on this!

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Re: Carbonating in PET

Post by PeeBee » Tue Jul 11, 2017 10:01 am

Headspace? I guess there is a lower proportion of headspace to beer in the PET bottles than the mini-keg. More headspace, more CO2 available to dissolve (assuming force carbonating). If this is right, don't fill the PET bottles so high. Natural conditioning (with the yeast in the beer) has no such concerns, the CO2 dissolves in the beer as soon as the yeast in the beer creates it.
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Re: Carbonating in PET

Post by AnthonyUK » Tue Jul 11, 2017 11:39 am

I've been using my carb caps a lot recently (for soda) and they work so much better with a dip tube e.g some CO2 tube attached than without so I think the headspace isn't the issue but the delivery method.

I think for best force carbing we should be doing this via the out post e.g. the one with the dip tube rather than the in post with the much shorter tube to get the CO2 into solution quicker.

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Re: Carbonating in PET

Post by Jambo » Tue Jul 11, 2017 7:37 pm

AnthonyUK wrote:I've been using my carb caps a lot recently (for soda) and they work so much better with a dip tube e.g some CO2 tube attached than without so I think the headspace isn't the issue but the delivery method.
Yep I achieve the same thing by inverting the bottle :)
AnthonyUK wrote: I think for best force carbing we should be doing this via the out post e.g. the one with the dip tube rather than the in post with the much shorter tube to get the CO2 into solution quicker.
In a corny keg, yes agreed, I do this if I'm in a rush and I think it helps.

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