# 1 way valve bags or not



## DavecUK

Those of you who know me may remember I have experimented with vacuum packing coffee and other observations many years ago on the staling of coffee. especially the perpetration of this myth, apparently originating from Illy.

That carbon dioxide-up to 10 liters per kilo of coffee for dark-roasted coffee, owing to the long roasting time-naturally releases from the beans over a period of weeks after roasting, rapidly over the first few days, then more gradually over the remainder of what's called the degassing period.

I came to a few inescapable conclusions from tests I did over 7 years ago. Interestingly a more recent blog post made me revisit the work again.

1. The gas in coffee is not there held within the structure after roasting, if there is any small trapped amount it's not 10 litres per kilo, or even a minute fraction of that amount

2. Vacuum packing coffee reduced the amount of CO2 formation

3. reopening a Vacuum pack starts the CO2 forming all over again

4. O2 exposure was responsible for the staling and most of the CO2 formation, although I do think a very small amount is fromed from post roast chemical reactions over time.

I then read this blog post from 3 years ago and he certainly seems to have found the same as me.

https://agoodkeensavage.wordpress.com/2012/01/17/why-i-stopped-packaging-our-coffee-in-one-way-valves/

Now I vacuum packed and found the coffee was much better and only seemed to begin staling after opening....it being very gassy even 2 weeks post roast. I also felt the flavour was better. BUT, the 1 way bags were very unreliable, didn't seal well all the time and often developed slight leaks. So reading this guys blog post reminded me again that I had intended to move things along a bit with my testing. Unfortunately the purchase of 500 one way valve bags rather hindered that









As I had purchased a impulse heat sealer, because the 1 way coffee pouches I was using would work very well and didn't like the heat from hair straighteners, I though I could experiment again. no I am cheap and I had some fairly think ziplock sandwich bags available that would take almost 450g of coffee. Thicker and better quality would have been better, but these were all I had to hand. With careful handling I could avoid leaks and squeeze most of the air out before closing the ziplock and then heat sealing the plastic above. I conducted experiments for around 8 weeks now and found that as long as coffee was placed in the bags soon after roasting.

1. They puffed up a little, but didn't burst, in fact the cheapness of the bag might have helped a little here, because they were slightly stretchy. Really though they didn't puff up much at all

2. Roast sharers who had the coffee packed like this were not aware of why, just that I was experimenting commented that even after 3 weeks a fresh opened bag behaved like coffee roasted only a few days old producing loads of gassy crema.

3. Personal observations I had supported this

In fact I opened a bag of Harrar roasted 7 days ago and the Harrar required a finer grind than I would expect for Harrar, then unusually the grind rather than staying the same has needed to become progressively coarser over the last 3 days. This is not the behaviour you tend to see, normally it's coarser and getting finer as the coffee ages. However, coffee drunk only a day or so post roast has to be ground finer and then goes a little coarser as it ages a few days and then you start going finer again. This coffee a week post roast was behaving more like a coffee 1 or 2 days post roast.

I think once my current stock of 1 way valve bags is gone, I will get the (much cheaper) bags without valves in future and for now, put some tape over my one way valves!


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## froggystyle

What one way bags do you have, 250g 500g 1kg ?

Looking for some if you want sell?


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## Phil104

Thank you - an interesting and informative piece. I use the AirScape containers, which I think do the same job that you describe in that they push all the air out and don't let anything back in (apart from you open it).


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## ZachChipp

Its a very interesting subject!

I know a lot of roasters (Including myself), will leave coffees after roasting for a short time before packing as this helps degas the coffee so wont be too much pressure on the packaging.

Also the aging of coffee after roasting can sometimes better the taste of coffee (Somewhere between 7-14 days), so vacuum packing would surely decrease this meaning that if you roasted a coffee and imedietly vacuum packed it and opened it 14 days later it would still taste (almost) as fresh as day 1?


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## MWJB

What does a litre of CO2 weigh? Was Illy referring to whole bean or ground?


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## ronsil

I remember the early trials with this. I used vacuum bags for a long time but always the seals seemed to go.

Since those days I graduated to 'Airscape' containers which I have found to be very effective. I also use an air evacuation canister introduced to me by Coffee Compass. I think Richard gave DSOL members a canister as a Christmas gift early on.

Both these systems work very well. Enables me to always have 2-3 different beans on the 'go'


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## DavecUK

MWJB said:


> What does a litre of CO2 weigh? Was Illy referring to whole bean or ground?


1 litre of CO2 weighs approx 0.113g, I don't know if Illy was referring to whole bean or ground coffee and I don't think it matters, the Myth expounded about the internet and seems to have become "fact" is that there is CO2 trapped in the bean (approx 10 litres per kg) and grinding breaks up the coffee and allows this "trapped" gas out. Which I have always thought is complete rubbish, my views backed up by experiment and observation.



ZachChipp said:


> Its a very interesting subject!
> 
> I know a lot of roasters (Including myself), will leave coffees after roasting for a short time before packing as this helps degas the coffee so wont be too much pressure on the packaging.
> 
> Also the aging of coffee after roasting can sometimes better the taste of coffee (Somewhere between 7-14 days), so vacuum packing would surely decrease this meaning that if you roasted a coffee and imedietly vacuum packed it and opened it 14 days later it would still taste (almost) as fresh as day 1?


Well 2 points there. I find if coffee is left for a day or so, it actually seems to produce more gas when packed, than if it's packed very quickly after roasting.

As for the ageing of coffee, I have found that coffee packed in very little air, does indeed taste much fresher when first opened. There are still some reactions happening that do age the coffee, but nowhere near as much as if Oxygen gets into the bag e.g. back through the 1 way valves...although good one way packaging does prevent this if the bag retains pressure and a slightly positive closing good quality Wico valve is used. It's just I don't think a 1 way valve of any kind is even necessary, making packaging much cheaper. cos very good 1 way valve bags are really expensive. mine are nearly £220 inc VAT for 500 (min box quantity) and unless your order 2 boxes shipping is about £25, cos they're quite heavy.

https://www.thebagbroker.co.uk/sup/1kg-stand-up-pouch-with-zip-and-valve-matt-black.html

One thing about vacuum packing, whenever I talk about it as per the tests I did, I got most of the eair out, but never sucked so much out as to create a "brick" or low pressure packaging for the coffee....I think that's a bad thing to do.


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## MWJB

DavecUK said:


> 1 litre of CO2 weighs approx 0.113g, I don't know if Illy was referring to whole bean or ground coffee and I don't think it matters, the Myth expounded about the internet and seems to have become "fact" is that there is CO2 trapped in the bean (approx 10 litres per kg) and grinding breaks up the coffee and allows this "trapped" gas out. Which I have always thought is complete rubbish, my views backed up by experiment and observation.


I thought a litre of CO2 weighed nearly twenty times that (1.977g/l), which could be the source of some misunderstanding? To be fair, your quote from Illy says "up to", not a minimum, or baseline.


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## DavecUK

MWJB said:


> I thought a litre of CO2 weighed nearly twenty times that (1.977g/l), which could be the source of some misunderstanding? To be fair, your quote from Illy says "up to", not a minimum, or baseline.


My apologies I did the calc in my head from memory and I was using wrong numbers, it probably is around 2g, but I don't really know what that has to do with anything to be honest, so I didn't take much care in checking out the number. However, I am sure you are completely correct.

It's not my quote from Illy what I said was



> Those of you who know me may remember I have experimented with vacuum packing coffee and other observations many years ago on the staling of coffee. especially the perpetration of this myth, apparently originating from Illy.
> 
> That carbon dioxide-up to 10 liters per kilo of coffee for dark-roasted coffee, owing to the long roasting time-naturally releases from the beans over a period of weeks after roasting, rapidly over the first few days, then more gradually over the remainder of what's called the degassing period.


The Key word is "apparently"...it's become a statement used in various forms by many people. You say "to be fair it states up to"...sure the one grabbed from the web used by someone else does say that...but Mark do you think "up to" means the guy thinks it's more like 10 l than 1l? If people meant 1 or 2 litres then they would say about 2 litres, not up to 10. However, all this misses the point, it's the internet Myth I'm talking about. I have seen stated so many times that this gas (10 litres) is trapped within the beans structure....and it's not. If there is any "trapped" CO2 it's miniscule, the vast bulk of CO2 production is from staling with Oxygen.

In fact after writing this entire post including what came below, I went and checked exactly what Illy said (you can read it for yourself) 6.1.2.1

https://books.google.co.uk/books?id=AJdlfSFCmVIC&pg=PA236&lpg=PA236&dq=10+litres+of+co2+in+roasted+coffee&source=bl&ots=mk5o-dFRkO&sig=3zu1COVzidNeN0xlOZp58HONY6M&hl=en&sa=X&ved=0ahUKEwjstPCEobrKAhXJCBoKHdVxAlQQ6AEIJzAB#v=onepage&q=10%20litres%20of%20co2%20in%20roasted%20coffee&f=false

So to get back to the Myths around the so called "degassing"

1. CO2 is trapped as a gas within the bean (no it's not, not in any significant amount)

2. Beans produce significant amounts of CO2,as "up to" could mean 0.00000000001 to 10 litres, so to try and be a bit more real world. I'm going to say 6-10 litres of CO2 even in the absence of O2 (No they need Oxygen to produce the CO2, although I believe some small amounts are possibly produced from other reactions...the Oxygen in the packaging and adsorbed from the surface of the bean during roasting and packing produce the initial gassing)

3. Degassing continues for some weeks then stops (well perhaps, but only if the coffee is exposed to air, if you exclude the air they produce CO2 for a while, then stop, expose them to air a month later and they start producing CO2 again).

*They're myths in various forms around the internet and I know they're myths because observation and experimentation does not support any of them. I have for months now been packing coffee in totally sealed bags very soon after roasting, a little gas is produced do to initial O2 exposure and what's in the bag, but not enough to burst the bag*. These bags are almost completely full, with a less flexible bag I would leave a little more headspace for expansion. Most importantly, the coffee seems better packed this way and fresher for longer. I have roasts 6 weeks old that pulled as if they were roasted Yesterday and are initially too lively for a few days. The only thing I have noted is that the staling process then proceeds more rapidly the older the beans are when you first open them

e.g. 1 week roasted and opened, will stale within 2 weeks, 6 weeks opened and roasted might stale within 1 week...by stale here I mean, reach a point where flavour is not optimum any more (all times approx).

This means I know where I'm going with Coffee pouches after this in terms of Valves, as many times valves are less than perfect...

You appear have some thoughts on all this, why not share them....because there is lots of science quoted, but it's not backed up by what actually happens and I'm not the only roaster saying so any more!


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## MWJB

DavecUK said:


> You appear have some thoughts on all this, why not share them....because there is lots of science quoted, but it's not backed up by what actually happens and I'm not the only roaster saying so any more!


My thoughts really relate to how you have determined this is an "internet myth", the source quoted is a published book. Also, what tests have you done to establish the claim is false (despite it being cited with regard to two other parties - Clarke, 1987; Shimoni & Labuza 2000), or the actual CO2 content of beans at various stages post roast?

I'm all for exploding myths, internet or otherwise, but doing so should be at least as robust as whatever method established the myth in the first place.

Whatever bags you use & are happy with is entirely up to you & perhaps a related issue rather than being in direct contradiction to the consensus you referenced?


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## DavecUK

MWJB said:


> My thoughts really relate to how you have determined this is an "internet myth", the source quoted is a published book. Also, what tests have you done to establish the claim is false (despite it being cited with regard to two other parties - Clarke, 1987; Shimoni & Labuza 2000), or the actual CO2 content of beans at various stages post roast?
> 
> I'm all for exploding myths, internet or otherwise, but doing so should be at least as robust as whatever method established the myth in the first place.
> 
> Whatever bags you use & are happy with is entirely up to you & perhaps a related issue rather than being in direct contradiction to the consensus you referenced?


Well I've actually tried it Mark, done it for real so to speak, what's in the book doesn't add up to what happens in reality. If you want to believe a published book makes it accurate and factual fine. As for robust the Illy stuff quotes a lot of technical looking stuff, but when you examine various papers, there's not much substance there.

What I have tried is tests around:

1. Vacuum Packing coffee and observed what happens

2. Packing Coffee in sealed bags and observed what happens

3. Tested whether coffees stop degassing and then start again when exposed to Oxygen

What happens does not support the assertions being made by Illy.....not much more I can do is there. Perhaps you should try your own tests (ones that meet your own requirements for accuracy) and see what you come up with. I used to believe it all, but over time I noticed things that didn't really seem to make sense against the accepted views of what happens or Illys papers.


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## hotmetal

13 valve bags


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## MWJB

DavecUK said:


> What happens does not support the assertions being made by Illy.....not much more I can do is there. Perhaps you should try your own tests (ones that meet your own requirements for accuracy) and see what you come up with. I used to believe it all, but over time I noticed things that didn't really seem to make sense against the accepted views of what happens or Illys papers.


I don't doubt what you observed, but I still don't see how you have demonstrated Illy et al are wrong.

You said that the zip lock bags puffed up but didn't burst. We don't know how much CO2 it takes to burst the bag, ~2g of CO2 occupies 1litre at standard temp & pressure. Presumably to burst a bag, the CO2 would need to be under pressure? The blog you linked to did say that 1kg bags were bursting and that they reverted to valved bags for 1kg.

Coffee has been vacuum packed since before I was born, so I doubt that this was something unknown to Illy.


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## DavecUK

MWJB said:


> I don't doubt what you observed, but I still don't see how you have demonstrated Illy et al are wrong..


OK Mark...interesting discussion, but it's really no more than that....I know what's working for me here and what I see happening. It's not just theory. You have a view based on what you have read, I have one based on what I am finding actually happens, best we leave it at that, because no value is gained by any more discussion.


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