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Author Topic: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!  (Read 5621 times)

Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #30 on: May 17, 2016, 01:44:00 pm »
The chart is titled orange oil, not orange juice. Also missing the timeline.


True, but there,'s plenty of evidence of scalping from juice discussed in the paper too. The timescale is in the text:
"About 70% of limonene was lost from cold-pressed orange oil in contact with LDPE for 4 d"

Not that limonene is important to brewers. Also pH found to make no difference to scalping of limonene.


Offline Stevie

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #31 on: May 17, 2016, 01:51:12 pm »
What about surface area? Was it five gallons of oil in a 5-6 gallon container?

I'm not crapping on what you found outright, I'm just pointing out where there could be differences.

My Better Bottles smell clean and they are 5+ years old. I used buckets for years, and yes, they did hold a bit of an aroma. This is partly why I'm hesitant to upgrade to Speidel fermenters.

Doesn't Leos ferment in modified conical storage tanks?

Offline toby

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #32 on: May 17, 2016, 02:20:00 pm »
My Better Bottles smell clean and they are 5+ years old. I used buckets for years, and yes, they did hold a bit of an aroma. This is partly why I'm hesitant to upgrade to Speidel fermenters.

http://www.better-bottle.com/technical.html

Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #33 on: May 17, 2016, 02:31:39 pm »
What about surface area? Was it five gallons of oil in a 5-6 gallon container?

I'm not crapping on what you found outright, I'm just pointing out where there could be differences.

My Better Bottles smell clean and they are 5+ years old. I used buckets for years, and yes, they did hold a bit of an aroma. This is partly why I'm hesitant to upgrade to Speidel fermenters.

Doesn't Leos ferment in modified conical storage tanks?

It's not my research so feel free to crap on it. The orange oil research paper is referenced in the bibliography in the link I posted.

PET is much better than other plastics as far as I can tell. It better be as I brew all my beers in it.

Offline Phil_M

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #34 on: May 17, 2016, 02:38:15 pm »
Two weeks might be enough for a significant effect. My plastic fermenters still smell of hop weeks after thorough cleaning and bleaching, so I reckon some scalping does happen in an average fermentation. Also, note that some flavours get scalped quicker than others - the paper says that absorption of citrus flavours by LDPE (low density polyethylene) is "instantaneous". I think scalping or contamination is the most plausible explanation for the exbeeriment result. I'm not convinced by the starsan theory.

I completely agree that your theory sounds more plausible. I just brought up my starsan theory because it is theoretically possible. The starsan is merely another variable to consider.
Corn is a fine adjunct in beer.

And don't buy stale beer.

Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #35 on: May 17, 2016, 02:48:09 pm »
Another possibility is a false positive - it's got to happen sometimes. That was my gut reaction until I remembered something I'd read about crown cap liners zapping hop aromas.

Offline denny

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #36 on: May 17, 2016, 02:53:31 pm »
Another possibility is a false positive - it's got to happen sometimes. That was my gut reaction until I remembered something I'd read about crown cap liners zapping hop aromas.

How was that determined?
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Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #37 on: May 17, 2016, 04:04:22 pm »
A couple of references below. There's a paywall in the way of the full paper but you can read the abstract. Sierra Nevada have done similar research into plastic linings in cans.

http://pubs.acs.org/doi/abs/10.1021/acs.jafc.6b00031?journalCode=jafcau

http://beerpulse.com/2012/07/sierra-nevada-on-the-cans-vs-bottles-debate/

Offline HoosierBrew

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #38 on: May 17, 2016, 04:15:31 pm »
A couple of references below. There's a paywall in the way of the full paper but you can read the abstract. Sierra Nevada have done similar research into plastic linings in cans.

http://pubs.acs.org/doi/abs/10.1021/acs.jafc.6b00031?journalCode=jafcau

http://beerpulse.com/2012/07/sierra-nevada-on-the-cans-vs-bottles-debate/




Thanks for posting. I'd read about oxygen scavenging caps absorbing hop aromas before. My takeaway is to keep kegging as much as possible and only bottle hoppy beers when necessary (for comps, gifts,etc.). I do dry hopping in the keg which is a plus.
Jon H.

Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #39 on: May 17, 2016, 04:25:33 pm »
Yes kegs probably give maximum hop aroma and quickest grain to glass time, which also helps avoid fading over time. You can get good results in bottles - perhaps just need a bit more dry hopping to compensate.

Offline erockrph

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #40 on: May 18, 2016, 09:08:41 am »
The chart is titled orange oil, not orange juice. Also missing the timeline.


True, but there,'s plenty of evidence of scalping from juice discussed in the paper too. The timescale is in the text:
"About 70% of limonene was lost from cold-pressed orange oil in contact with LDPE for 4 d"

Not that limonene is important to brewers. Also pH found to make no difference to scalping of limonene.
Actually, limonene is quite important to brewers. It is a pretty important constituent in hop oil (as are several of the other oils in that graph - myrcene is the other big one that jumps out to me). Limonene is a major player in creating the citrus flavor and aroma from hops.

One critical difference between fermenters and packaging containers like juice bottles is that we reuse our fermenters. Once the plastic gets "seasoned" (for lack of a better term), it should be relatively saturated with adsorbed flavor compounds and will scalp less of the compounds in successive batches. Or at least that is my WAG about this.  :D
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Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #41 on: May 18, 2016, 12:25:52 pm »
Actually, limonene is quite important to brewers. It is a pretty important constituent in hop oil (as are several of the other oils in that graph - myrcene is the other big one that jumps out to me). Limonene is a major player in creating the citrus flavor and aroma from hops.

Interesting, I didn't know hops contain limonene. It's a flavour I associate with scented soap and candles - hopefully not too strong in hops.


One critical difference between fermenters and packaging containers like juice bottles is that we reuse our fermenters. Once the plastic gets "seasoned" (for lack of a better term), it should be relatively saturated with adsorbed flavor compounds and will scalp less of the compounds in successive batches. Or at least that is my WAG about this.  :D

Possibly, but the fact that plastic smells of hops after use suggests the oils are still volatile and can escape again. Polyester t- shirts have the same property - even a thorough wash doesn't remove the smell but airing for long enough does.

Offline blair.streit

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #42 on: May 18, 2016, 12:35:52 pm »
Possibly, but the fact that plastic smells of hops after use suggests the oils are still volatile and can escape again. Polyester t- shirts have the same property - even a thorough wash doesn't remove the smell but airing for long enough does.
You may have just saved my favorite brewery t-shirt from extinction (or I guess more accurately ex-"stink"-tion) :)

Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #43 on: May 18, 2016, 01:59:21 pm »
It works for me but YMMV...