Glass or Plastic for Bottling

[David Woods]

So, I brewed an all grain Amber Ale and I decided to bottle this one in my Coopers PET bottles as I thought it may not turn out too good as I struggled a bit with the brew temp - I also put some in glass (brown) bottles too.

Anyway some weeks later the beer tastes great, a nice Amber ale with a fab malty taste and very moorish (it's nearly all gone!) but only from the PET bottles. The same brew from the glass bottles tastes very harsh and nowhere near the same taste profile. It's taste is nowhere near as good and almost tastes like a different beer. The bottles were all cleaned and sanitised properly so I don't understand why the PET bottled beer is so much better.

Any gurus out there got an idea why? I would have assumed the "proper" bottles would be the best but the PET beer is softer, more rounded with an absolutely fab taste where the glass beers are not as nice to drink.

Upcoming brews are going into kegs so wondering which flavour I will get from the keg

Look forward to the replies for the next brew.
Cheers all.

 

[dad_of_jon]

Are the glass bottles clear? although I can't imagine them getting light-struck this time of year. did both types of bottles get the same cleaning/rinsing regime?

The difference between glass and plastic to absorb heat. Not sure if this will make a difference depending on your temperature control as the liquid within the container absorbs around 5 times the amount of heat as glass so the choice of container re: temps is not significant.

The only other thing I can think of off the top of my head is how well are the containers sealed and do they have the same amount of headspace?

 

[David Woods]

Yes, all bottles had the same treatment - good cleaning (I clean them properly after drinking from them anyway) and sanitising. They have the same headspace when bottling and the glass bottles are brown (not clear) - I tighten the PET bottles as much as I can and the beers seem to have the same carbonation so no idea why the difference.

It seems like the glass bottles have all the taste flavour missing and only the bitterness and a thin beer left while the PET bottles just seem so much better.

All bottles were conditioned and stored exactly the same way - two weeks in a warm room in the dark then in a colder space before drinking. It is a mystery to me.

 

[sifty]

Weird.
Could you have someone set up a blind taste test to see if you don't have an unconscious bias...?

 

[David Woods]

I don't think I have a bias - of course I know what I am drinking from - although I have a mate who will drink and really like whatever he is given... then again it is free beer!

I take your point but the difference is very marked. I will get the wife to blind test me - but I suspect she will try and wean me away from beer!

 

[Nucbrewer]

Did you batch prime or add sugar or carb drops to each bottle?

 

[MashBag]

The clue for me was "some weeks".

PET is gas permiable. Glass and stainless are not.
Google "pet gas permeability"

Oxygen reacted with the beer and improved it. Just like it does hanging meat.

The homebrew community have a phobia of oxygen, but it is your friend.

 

[An Ankoù]

Anyway some weeks later the beer tastes great, a nice Amber ale with a fab malty taste and very moorish (it's nearly all gone!) but only from the PET bottles. The same brew from the glass bottles tastes very harsh and nowhere near the same taste profile. It's taste is nowhere near as good and almost tastes like a different beer. The bottles were all cleaned and sanitised properly so I don't understand why the PET bottled beer is so much better.

That;s an interesting one, Not least trying to understand why the beer tastes North African!

If the bottles are equally clean, and there;s no reason to suppose they shouldn't be then perhaps it;s an oxygen thing. This could go either way: PET is more permeable than Glass and so there could be a little more contact with the air and this would make the beer taste a little more "cask" since casks admit air as the beer is drawn out. I don't believe this one, though, as Coopers PETs are designed to hold beer and probably have some kind of lining, and, the oxygen in the headspace would have more immediate influence on the beer in the short term. Which brings me to the second: PETs are not rigid and there is the tendency to squeeze as you screw the cap on. This reduces the headspace and the available oxygen. Or you may have chosen to squeeze out the headspace knowing that the bottle will regain its shape as it pressurises.
Either way, I'm surprised there was a noticeable difference in such a short space of time. In any case, I doubt the Moors would have drunk beer since they were of the Muslim persuasion.

 

[An Ankoù]

Oxygen reacted with the beer and improved it. Just like it does hanging meat.

The homebrew community have a phobia of oxygen, but it is your friend.

Can't agree with you there @MashBag , I can't think of any beer that is improved by prolonged exposure to air. Sure, the beer halfway down a fresh cask, or a biêre de dégustation half way down the glass will likely taste better, but that's as much due to the CO2 leaving the beer as anything else. Nobody likes stale beer. Unless you can give us an example of where it might be improved
On the other hand, I do believe in exposing homebrew superstitions. Clear bottles (ex cider bottles 500ml, for example). Received wisdom has it that if you put your beer in clear bottles you'll die!
Rubbish. Clear bottles are easy to fill, easy to see how clear the beer has become and easy to avoid pouring the "bottoms" into your beer. Put them in a box or a dark cupboard. It's only UV light that spoils the beer. We don't need to display our beer on flourescent -lit supermarket shelves.

Edit:
In retrospect, it may well be that transient and intermediate oxidation products are formed in the glass which quickly degenerate in to spoilage compounds, something akin giving red wine time to "breath" before necking it down.

 

[David Woods]

Sorry, "moreish"!

 

[An Ankoù]

Sorry, "moreish"!

I've done it myself, which is why I noticed.

 

[MashBag]

Can't agree with you there @MashBag , I can't think of any beer that is improved by prolonged exposure to air.

Surely that depends on where it was to start with.

Maturing is the upside of the bell curve, staling is the downward side.

Ps. Brilliant point about clear glass. 1m% agre. It is so indemic coopers don't make a clear PET

 

[Sadfield]

@David Woods Looking at your other threads it looks like you brewed this beer in early November, and it fermented quickly. Is that correct?

Ordinarily, most beers are intended to be drunk young, so oxidation is regarded as a negative. However, there are a number of ways oxidation can change a beer through ageing. Unpleasant, harsh higher alcohols can oxidise into aldehydes with bready, toffee and amaretto notes. And malt flavour can go a number of ways, stale cardboardy or sweeter. Another way is esters can change, fresh fruity ones can change to dried fruit. Both of which could change an Amber, pleasantly. Bitterness is going to mellow over time. It used to be a lottery years ago with buying imported US IPAs, you'd either get a hop bomb or chewy toffee, almost barleywine type beer, through poor storage and transit.

It could be that the glass bottles retained some off flavours created by the problems you had, and some bitterness.

 

[Sadfield]

Geared to collecting and drinking rather than brewing, Vintage Beer by Patrick Dawson is an informative read with regards to how beer changes over time.

 

[Twostage]

My only contribution above whats already been said would be 'lids'. Something about the bottle caps ?

 

[ARNWD]

@David Woods

Did you bottle direct from the fermenter or a bottling bucket?

Did you fill the PET bottles first, then fill the glass bottles?

Did you bottle from a tap or via a syphon?

 

[peterpiper]

Some people still get good results, barrel ageing non-soured beers, in wood (oak) barrels. I'd guess these (even when full) are still much more gas permeable than PET bottles. So with some beer styles, maybe oxygen does help.


Permeability testing done on various PET beer bottles, in a 100% O2 environment, gave figures ranging from 0.02 ml /500ml bottle /day to 1.5ml / 650ml bottle /day. Nearly a 100 to 1 variation!
The best results were from brown and green bottles. These may well have been multi-layer barrier PET bottles (a similar idea to barrier pipes), as it's diffucult to get non-permeable layer that's transparent.

Coopers PET beer bottles, have a barrier layer, and oxygen scavanging lids. The bottles are sold as re-useable, but the scavenging action would probably only work well on first fill.
Replacement lids cost under 10p.

If it was your Coopers bottle lids first use (where the lids scavenged any oxygen), and your glass bottles weren't purged of headspace oxygen (replaced by CO2). Then the beer in PET would have less oxygen, than beer in glass, for many months.

 

[MashBag]

Imo Oxygen scavenging caps really aren't an issue for homebrewed ale. Designed and used extensively for packaging commercially brewed bright beer.

If both filled & sealed correctly glass will beat PET shelflive* by miles. Plastic is used extensively to bring beverages on not preserve statsis. I have used 25l HDPE expressly for its maturing qualities.

* there's a thought. Never seen beer for sale in PET..... is there any?

 

[peterpiper]

Glass probably better for storage 6month+.
But for a homebrew, consumed within a few weeks, it may be better in PET. Especially if no other way of purging oxygen is available.

I've never tried carbonating beer in PET, but now quite tempted to try Coopers bottles, for a comparison.

 

[fluketamer]

i used clear PET bottles for years . stouts stored at 64 degrees were fine up to about 4-5 months then start to lose carbonation . lighter beers i never let go more than 2 months cause i drank them fresh but never had a problem with oxidation.

2 weeks ago my brother sent me this text:

i brewed this in november of 2019.

and it was a coopers stout kit.

he reported no off flavors.

4 years in a PET bottle. im sure the 36 degree fridge kept it viable but still . kit beer 4 years in a pet bottle.

love my coopers and you can bottle in pet its not an issue.

im not saying pet is better than glass that makes no sense but nothing wrong with PET.


"I don't think I have a bias" - nobody does thats why blind tests were invented.

i have had great success kegging in 2.5 and 3.5 liter amber PET bottles.