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Author Topic: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!  (Read 5625 times)

Offline Joe Sr.

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #15 on: May 16, 2016, 12:38:25 pm »
I use glass. I can be more aggressive with cleaning techniques without having to worry.

How aggressive do you need to be?  A good soak takes most everything off.  What's left can usually be gotten with a soft cloth or rag stuffed through the neck of the fermenter.

If you're scraping crust off the inside, you need to soak it longer.
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Offline Phil_M

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #16 on: May 16, 2016, 12:51:28 pm »
I've had a couple (long, 4+ week) fermentations were the brown scum was pretty well dried on. After a long soak with Alkaline Brewer's Wash I still had to break out the carboy brush to get it all off.  So, not that aggressive, but I'd be concerned with the effects of a stiff bristled brush on plastic over time.

By the way, I'm not calling the beer infected. I'm thinking more along the lines of brewers yeast from a different batch staying behind.
Corn is a fine adjunct in beer.

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Offline brulosopher

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #17 on: May 16, 2016, 02:12:38 pm »
This is likely a weak limb to try and explain the difference, but what sanitizer was used?

Glass always seems to clean up better than plastic. If star-san was used, it's possible something was "left behind" in the plastic fermentor that was successfully washed out of the glass one.

Either way, I'd say that cleanliness is more of a concern for most brewers when choosing between glass and plastic, not oxidation. But that's just my hunch.

I use glass. I can be more aggressive with cleaning techniques without having to worry.

StarSan. This is an interesting theory, for sure. I make sure to get as much out of my carboys as possible prior to filling with wort, which for my PET carboys involves gently applying pressure to shoot the bubbles out... you can't do that with glass.

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #18 on: May 16, 2016, 02:24:56 pm »
This is likely a weak limb to try and explain the difference, but what sanitizer was used?

Glass always seems to clean up better than plastic. If star-san was used, it's possible something was "left behind" in the plastic fermentor that was successfully washed out of the glass one.

Either way, I'd say that cleanliness is more of a concern for most brewers when choosing between glass and plastic, not oxidation. But that's just my hunch.

I use glass. I can be more aggressive with cleaning techniques without having to worry.

StarSan. This is an interesting theory, for sure. I make sure to get as much out of my carboys as possible prior to filling with wort, which for my PET carboys involves gently applying pressure to shoot the bubbles out... you can't do that with glass.

Star San has been noted to be a yeast nutrient in a minor way.  If that's so, it would seem that the plastic batch, assuming it retained StarSan (which is a pretty long shot), would have had an advantage, not disadvantage, over glass.
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Offline brulosopher

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #19 on: May 16, 2016, 02:26:17 pm »
This is likely a weak limb to try and explain the difference, but what sanitizer was used?

Glass always seems to clean up better than plastic. If star-san was used, it's possible something was "left behind" in the plastic fermentor that was successfully washed out of the glass one.

Either way, I'd say that cleanliness is more of a concern for most brewers when choosing between glass and plastic, not oxidation. But that's just my hunch.

I use glass. I can be more aggressive with cleaning techniques without having to worry.

StarSan. This is an interesting theory, for sure. I make sure to get as much out of my carboys as possible prior to filling with wort, which for my PET carboys involves gently applying pressure to shoot the bubbles out... you can't do that with glass.

Star San has been noted to be a yeast nutrient in a minor way.  If that's so, it would seem that the plastic batch, assuming it retained StarSan (which is a pretty long shot), would have had an advantage, not disadvantage, over glass.

Sorry, I wasn't clear-- I'm able to squeeze almost every last bubble out PET, while the glass retained more bubbles because I could only rely on shaking over my sanitizer bucket.

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #20 on: May 16, 2016, 02:28:09 pm »
Sorry, I wasn't clear-- I'm able to squeeze almost every last bubble out PET, while the glass retained more bubbles because I could only rely on shaking over my sanitizer bucket.

Thanks!
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Offline blair.streit

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #21 on: May 16, 2016, 03:30:55 pm »
This is likely a weak limb to try and explain the difference, but what sanitizer was used?

Glass always seems to clean up better than plastic. If star-san was used, it's possible something was "left behind" in the plastic fermentor that was successfully washed out of the glass one.

Either way, I'd say that cleanliness is more of a concern for most brewers when choosing between glass and plastic, not oxidation. But that's just my hunch.

I use glass. I can be more aggressive with cleaning techniques without having to worry.

StarSan. This is an interesting theory, for sure. I make sure to get as much out of my carboys as possible prior to filling with wort, which for my PET carboys involves gently applying pressure to shoot the bubbles out... you can't do that with glass.

Star San has been noted to be a yeast nutrient in a minor way.  If that's so, it would seem that the plastic batch, assuming it retained StarSan (which is a pretty long shot), would have had an advantage, not disadvantage, over glass.
So now we need a couple more xBMTs to compare "a little" residual StarSan versus none, and none versus the crap ton that you get if you cold crash while leaving the blowoff tube in the bucket of StarSan :P

Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #22 on: May 16, 2016, 04:57:42 pm »
This might be relevant:

Scalping of Flavours in Packaged Food
http://tinyurl.com/hwcf4lu

Offline brewinhard

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #23 on: May 16, 2016, 04:58:53 pm »
This is likely a weak limb to try and explain the difference, but what sanitizer was used?

Glass always seems to clean up better than plastic. If star-san was used, it's possible something was "left behind" in the plastic fermentor that was successfully washed out of the glass one.

Either way, I'd say that cleanliness is more of a concern for most brewers when choosing between glass and plastic, not oxidation. But that's just my hunch.

I use glass. I can be more aggressive with cleaning techniques without having to worry.

StarSan. This is an interesting theory, for sure. I make sure to get as much out of my carboys as possible prior to filling with wort, which for my PET carboys involves gently applying pressure to shoot the bubbles out... you can't do that with glass.

Star San has been noted to be a yeast nutrient in a minor way.  If that's so, it would seem that the plastic batch, assuming it retained StarSan (which is a pretty long shot), would have had an advantage, not disadvantage, over glass.
So now we need a couple more xBMTs to compare "a little" residual StarSan versus none, and none versus the crap ton that you get if you cold crash while leaving the blowoff tube in the bucket of StarSan :P

Not that this really means much, but I leave quite a bit of starsan foam in my carboys when I rack my beer from the kettle into it.  So much so, that as the beer displaces the foam it pushes it out right out the carboy and up the outside of my tubing. It actually acts as quite the barrier from anything falling into my carboy opening as the racking is underway. Beers come out great...

Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #24 on: May 17, 2016, 02:37:22 am »
This table from the paper in link above shows how flavors from orange juice are "scalped" by various plastics - basically the plastics absorb nonpolar aromatic compounds including many of the oils that are found in hops. Some of the flavour compounds in orange juice will look familiar to brewers:



There's only one para regarding scalping in beer:
Quote
For pale ale bottled in clear PET and PEN containers with plastic caps, and a glass control bottle with a crown closure, sensory, and physicochemical properties at the 14th wk, showed PEN bottles to have provided the best protection, followed by glass and finally PET (Goodrich 1997).

So glass is better than PET at preserving flavors. I've seen other sources saying that the plastic liner in crown caps can scalp certain hop aromas, but fortunately linalool (the sweet-smelling tropical terpene in Mosaic and Citra) doesn't get scalped by crown caps or PET.

« Last Edit: May 17, 2016, 02:40:03 am by charles1968 »

Offline Joe Sr.

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #25 on: May 17, 2016, 09:13:03 am »
How much does acidity affect flavor scalping?

OJ must be significantly more acidic than beer.  At least that's my non-scientific assumption.
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Offline blair.streit

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #26 on: May 17, 2016, 09:20:06 am »
How much does acidity affect flavor scalping?

OJ must be significantly more acidic than beer.  At least that's my non-scientific assumption.
The Google thinks your non-scientific assumption is pretty good:

Quote
Orange juice ranges in pH from 3.3 to 4.19. It has 122 calories, 139 percent of the DV for vitamin C, 12 percent of the DV for folate and 13 percent of the DV for potassium per cup. Its effect on tooth enamel, however, isn't clear.

It's not down in the mid 2's with the colas, but it is significantly lower than most non-sour beers (remember, pH is a logarithmic scale so the difference between 4.5 and 3.5 is pretty significant).

Not sure if that would impact how it interacts with the plastic, but it seems plausible.

Offline Stevie

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #27 on: May 17, 2016, 09:25:06 am »
The chart is titled orange oil, not orange juice. Also missing the timeline.

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #28 on: May 17, 2016, 10:00:28 am »
The chart is titled orange oil, not orange juice. Also missing the timeline.

Yeah, I'm skeptical of the equ8ivalence between this and beer.  Not to mention that beer stays in plastic only a week or 2 usually.
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Offline charles1968

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Re: Plastic (PET) Carboy vs. Glass Carboy | exBEERiment Results!
« Reply #29 on: May 17, 2016, 01:39:13 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.