Beer Bottles

[Steve Maskery]

I've noticed recently that more and more beer is being sold in clear glass bottles rather than brown. Now my understanding is that beer keeps longer in the dark, as light increases the rate of oxidation, so why are brewers doing this? Has brown glass suddenly become very expensive?
S

 

[Phil Pascoe]

I suspect it's because the brewers like to make more of the colour of the beer than they used to. The glass for clear bottles must be more expensive, I'd have thought, as once it's recycled it's bound to have a certain amount of colour in it?

 

[RogerS]

I've noticed recently that more and more beer is being sold in clear glass bottles rather than brown. Now my understanding is that beer keeps longer in the dark, as light increases the rate of oxidation, so why are brewers doing this? Has brown glass suddenly become very expensive?
S

I don;t know about that, Steve. My beer never stays long enough in the bottle...

 

[sdjp]

... my understanding is that beer keeps longer in the dark, as light increases the rate of oxidation, so why are brewers doing this?

Not quite - 'beer' doesn't have a problem with light, per se. It's the hops that can get light struck. It's not 'oxidation' in the technical sense; there's a couple of steps.

When the hops are boiled in the wort, the alpha-acids are converted to iso-humolones (and other compounds), which give the bitterness in the finished beer. This can then be broken down in a reaction with light (catalysed by other things in beer), to produce free radicals that then grab sulpher to form some very smelly thiols, in particular one called 3-methylbut-2-ene-1-thiol - or 3-MBT. These are the same compounds that skunks produce - hence the terms 'lightstruck' or 'skunked' to refer to beer that's been affected in this way.

However, there are a couple of ways of preventing it. One way is to not use hops! That's why ciders/meads/wines don't have the problem. Hops are a recent (1600's or so) additive in beer, 'gruit' is the term for the bittering agents pre-hops. (If you've not tried Williams Bros Fraoch, seek it out. It's got a tiny amount of hops in it, but is primarily bittered with heather.)

Another option is to use a hop extract that doesn't have iso-humolones - relying on other parts of the hop extract to provide bitterness. Millers does this, for example - it gives a slightly different hop bitterness, but it's not inherently a bad thing. I suspect that most of the beer sold in clear bottles is also done in this way.

I suspect that the manufacturers prefer to use clear bottles, because it's been well observed that the more a customer can see a product in the packaging, the more likely they are to buy it. Of course, when dealing with a beer aficionado, this will have the opposite effect, and small brewers almost certainly don't use fancy extracts, preferring to use actual hops.

I have seen the skunking effect in beer in a glass once. It was a hop monster IPA, outdoors on a particularly sunny day, and I could smell the thiols near the end of the pint. But that's rather unusual, especially in this country!

To be honest, if it's in a clear bottle, your nose will tell you instantly if there's a problem when it's opened. If it smells good, it's fine.

Stuart

 

[Random Orbital Bob]

Yes....these loose generalities are all very well...but I would at least have expected full "benzene ring" diagrams with detailed ionic or covalent bond descriptions! I mean really

Seriously though....cracking explanation

 

[Steve Maskery]

Quite a lot!

I don't think any post has ever been answered so fully.
Thank you very much.
Steve

 

[maltrout512]

... my understanding is that beer keeps longer in the dark, as light increases the rate of oxidation, so why are brewers doing this?

Not quite - 'beer' doesn't have a problem with light, per se. It's the hops that can get light struck. It's not 'oxidation' in the technical sense; there's a couple of steps.

When the hops are boiled in the wort, the alpha-acids are converted to iso-humolones (and other compounds), which give the bitterness in the finished beer. This can then be broken down in a reaction with light (catalysed by other things in beer), to produce free radicals that then grab sulpher to form some very smelly thiols, in particular one called 3-methylbut-2-ene-1-thiol - or 3-MBT. These are the same compounds that skunks produce - hence the terms 'lightstruck' or 'skunked' to refer to beer that's been affected in this way.

However, there are a couple of ways of preventing it. One way is to not use hops! That's why ciders/meads/wines don't have the problem. Hops are a recent (1600's or so) additive in beer, 'gruit' is the term for the bittering agents pre-hops. (If you've not tried Williams Bros Fraoch, seek it out. It's got a tiny amount of hops in it, but is primarily bittered with heather.)

Another option is to use a hop extract that doesn't have iso-humolones - relying on other parts of the hop extract to provide bitterness. Millers does this, for example - it gives a slightly different hop bitterness, but it's not inherently a bad thing. I suspect that most of the beer sold in clear bottles is also done in this way.

I suspect that the manufacturers prefer to use clear bottles, because it's been well observed that the more a customer can see a product in the packaging, the more likely they are to buy it. Of course, when dealing with a beer aficionado, this will have the opposite effect, and small brewers almost certainly don't use fancy extracts, preferring to use actual hops.

I have seen the skunking effect in beer in a glass once. It was a hop monster IPA, outdoors on a particularly sunny day, and I could smell the thiols near the end of the pint. But that's rather unusual, especially in this country!

To be honest, if it's in a clear bottle, your nose will tell you instantly if there's a problem when it's opened. If it smells good, it's fine.

Stuart

Brewers have taken a leaf out of the governments little book................................................... Transparency :roll: