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Tristan
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Post subject:
 Posted: Jan 20, 2009 - 08:36 AM
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Joined: Feb 14, 2007
Posts: 337
Location: Wadebridge, Cornwall
Status: Offline
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| Anyone know what happens if you don't have a valve? Does the CO2 have a detrimental affect on the coffee if not allowed to dissipate? |
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The Wild Drink Blog
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Expobar Brewtus II, Vario
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darrensandford
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Posted: Jan 20, 2009 - 09:14 AM
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Joined: Feb 21, 2008
Posts: 379
Location: Coventry, UK
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I know that I have bought coffee vac-packed in a heat-sealed bag, and within days the bag has ballooned up. Without that valve, I am sure the bag would've ruptured. I believe the CO2 in the bag has a beneficial effect, displacing the oxygen and therefore slowing staleing.
Thoughts? |
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Tristan
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Post subject:
Posted: Jan 20, 2009 - 12:28 PM
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Joined: Feb 14, 2007
Posts: 337
Location: Wadebridge, Cornwall
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Just done a bit of reading on this, let's see if I can make some sense of it.
CO2 is proportional to volatile compounds in the bean. CO2 will displace oxygen, which along with water are the two major factors in staling. Pressure on roasted coffee causes the bean pores to de-gas slower.
So it sounds like pressure is good as far as degassing goes, though we need some level of degassing before espresso application. Leads me to think that in an ideal world the coffee would degas with a one-way valve, then after being opened it would be transfered to a sealed vessel so that some pressure would build up.
I might try transferring my coffee into jars after opening...
Any thoughts? |
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The Wild Drink Blog
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Expobar Brewtus II, Vario
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Gwilym
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Posted: Jan 20, 2009 - 06:42 PM
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Joined: May 02, 2006
Posts: 191
Location: East London
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At work I receive my coffee in a reusable 4kg tub with a bag valve put into the lid.
This should be an easy enough process to put into a smaller container - better to buy one valve than many. |
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zix
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Post subject:
Posted: Jan 20, 2009 - 10:41 PM
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Joined: Mar 24, 2004
Posts: 1312
Location: Partille/Göteborg, Sweden
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The hopper itself should be good for at least a couple of days - right? Not that it is artight in any direction, but at least there is usually coffee powder in the grind chamber, and most hoppers have lids. If you add a simple rubber gasket on the rim of the hopper or the lid, perhaps also paint the hopper opaque... a hopper often takes around 250g coffee or so. Sometimes more.
You wouldn't need a valve, the CO2 would leak out through the grind chamber. Maybe a hopper isn't all that bad a bean bag after all? |
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JulieJayne
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Posted: Jan 22, 2009 - 11:04 PM
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Joined: Oct 04, 2005
Posts: 371
Location: Dordrecht, Nederland
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darrensandford wrote:
I know that I have bought coffee vac-packed in a heat-sealed bag, and within days the bag has ballooned up. Without that valve, I am sure the bag would've ruptured. I believe the CO2 in the bag has a beneficial effect, displacing the oxygen and therefore slowing staleing.
Thoughts?
If the bag was of suitable material and properly sealed, (under normal circumstances) it won't rupture. It looks far more dramatic than it actually is. The valves are added IMHO to avoid this ballooning effect, which scares customers.
However the valves also don't work the way people think. If untouched, by "bag squeezers", valved bags balloon in the same manner. |
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Espresso: BFC TCI Lira.
Grinders: Eureka Mignon (2), Mahlkonig Guatemala,
Roaster: Gene Cafe.
Retired... Cimbali Junior, Cimbali Alinox.
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Olings
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Post subject:
Posted: Jan 23, 2009 - 07:42 AM
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Joined: Jan 06, 2005
Posts: 371
Location: Oslo, Norway
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Second that JulieJayne. Our bags have a tendency to balloon up. People always ask questions about it. The hopper idea sounds more like wishful thinking than anything else. Sorry Zix it doesn't sound like a good idea to me. 
My advice is always to keep the beans in the bag even if you're going to transfer them into another container. Just keep them in the bag. The transferring will expose them to a lot more oxygen and the bag is doing the trick as it is. If you squeeze the air out of the bag after each time you poured some beans out, it'll work as good or better than most expensive vacuum gizmos out there and the bag comes free of charge. Besides we all drink our coffees in a matter of days, right?  So then the problem really isn't that big.
Ola |
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La Marzocco GS3, Compak K10, Dualit grinder, Turkish coffee maker (Ibrik) and grinder, Eva Solo coffee maker, French press, Aeropress.
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darrensandford
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Post subject:
Posted: Jan 23, 2009 - 09:18 AM
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Joined: Feb 21, 2008
Posts: 379
Location: Coventry, UK
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| I submit that the best use for the valve is so that you can gently squeeze the bag and get a little preview of what is to come, without opening the whole bag. Valve-sniffing is very important to me. |
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Post subject:
Posted: Jan 23, 2009 - 10:03 AM
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Joined: Oct 08, 2005
Posts: 71
Location: UK
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On the assumption that beans are packed fresh after roasting (i.e. within a few minutes) then laminate bags with no valve will typically fail after a few days (normally due to de-lamination at the top seal), i.e. if you want to pack fresh coffee into flexible packaging without a vacuum you need a valve. Reason being that 1 kg of coffee can release up to 10 litres of coffee gas during life (principally CO2 but with some CO and N2 thrown in); the volume being dependent on roasting parameters, cooling protocols and coffee species.
In the bad old days of vacuum packing, roasters used to ‘degas’ (or stale, depending on your viewpoint) ground coffee for 5-6 hours after grinding before packing it in vacuumed flexible packaging so consumers wouldn’t reject ‘balloon / soft’ packs on supermarket shelves. Ideally this ‘degas’ process was carried out under N2 or supplementary CO2.
The reason that bags fitted with a valve still balloon is that that the valves operate on an overpressure release, normally ~ 4-9 mbar with a flow rate of ~1 litre per minute, before closing again at ~0.5 mbar, although you can buy valves with different specs depending on the application. Work has been done using a selective carbon membranes fitted to valves to limit the loss of aroma volatiles via the degassing process although these didn’t produce a tangible difference to the cup from a sensory standpoint. |
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ivdp
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Post subject:
Posted: Jan 23, 2009 - 01:37 PM
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Joined: Sep 25, 2004
Posts: 384
Location: Lieren, The Netherlands
Status: Offline
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| Since we seem to agree that aging is not a favorable thing for coffee, why let coffee age? |
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KvdW Idro - M K30
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JulieJayne
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Post subject:
Posted: Jan 23, 2009 - 03:21 PM
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Joined: Oct 04, 2005
Posts: 371
Location: Dordrecht, Nederland
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ubo wrote:
On the assumption that beans are packed fresh after roasting (i.e. within a few minutes)
That is a massive assumption. I think in practice you should assume at least an hour or so, with most roasteries.
Quote:
then laminate bags with no valve will typically fail after a few days
Only if the bag is too small for the coffee it contains and the coffee is roasted to death. IME.
Quote:
The reason that bags fitted with a valve still balloon is that that the valves operate on an overpressure release, normally ~ 4-9 mbar with a flow rate of ~1 litre per minute, before closing again at ~0.5 mbar,
I believe you. But in the real world this means that valves don't add anything for the consumer, except cost.
In 5 years in this business, I have seen 3 non-valved 250 gram bags fail. On each occassion the coffee was too dark (oily). The side seam on these stand up pouches was the failure point.
In the same time period I have seen dozens of valved SUPs fail, always where the valve was fitted. And likewise tens of foil laminated kilo packs, which fail for various reasons. Too little heat at the top seal, too much heat, and failure of the back seal and the valve seal, and the bottom seal! |
_________________
Espresso: BFC TCI Lira.
Grinders: Eureka Mignon (2), Mahlkonig Guatemala,
Roaster: Gene Cafe.
Retired... Cimbali Junior, Cimbali Alinox.
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Post subject:
Posted: Jan 23, 2009 - 05:09 PM
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Joined: Oct 08, 2005
Posts: 71
Location: UK
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Will need to agree to differ on pack failure rates. I have trialled oil film valve systems (using ground coffee, light/medium roast, 100% arabica, air-cooled, i.e. low risk) packed off immediately after grinding (grinder feeding auger direct) and witnessed the pallet collapse as the packs ballooned causing outer case tape to fail. Pack failure rate was >60% within 3-days and the particular valve type couldn’t cope with the rate of gas release and required a degas time of ~4 hrs before filling could commence, needless to say we didn’t adopt that system.
On my packing time assumption, the dozens of roasting operations that I have visited over the years (especially those using form/fill/seal) would strive to pack straight after roasting (i.e. in minutes)… the valve allows them to do that. The rate limiting factor for packing time beyond that is the practicality of roasted coffee inventory management for post-blending and whether you believe in normalising the moisture gradient across the bean prior to grinding is significantly beneficial to particle size distribution.
To say that valves don’t add anything to the consumer except cost I find baffling. If you are packing fresh coffee on mechanised lines then they are a must to avoid pack failure, why else would they be in use? Are you seriously suggesting that all those roasters out there who have collectively invested $0,000,000’s in valve applicators and valves shouldn’t have? |
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zix
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Post subject:
Posted: Jan 23, 2009 - 08:42 PM
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Joined: Mar 24, 2004
Posts: 1312
Location: Partille/Göteborg, Sweden
Status: Offline
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Quote:
wishful thinking
ah, my favourite pastime
Quote:
Sorry Zix it doesn't sound like a good idea to me. :Wink:
You may be right. Still, I think that what with all the opening of the so called sealed bags with those fancy valves, too much oxygen gets in to the beans anyway. That's not to say a one-way valve bag isn't a good method for storing and distributing commercially roasted coffee. I am sure it is - until it gets opened, and all that oxygen starts staling our lovely coffee.
And then, we don't only open it once, we open it many times. Each time, new oxygen gets into the coffee bag.
I have tried pushing air out of such bags each time, very zealously, and also keeping a slack regime, only closing the bag and pushing the air out through the valve if I feel like it. Have seen little or no difference in the deterioration rate of my coffee. what does matter immensely is how fresh it is to begin with.
As an example, I just had the great luck of getting an unusually fresh bag of Musetti beans (el cheapo superstore espresso coffee, but whole beans). It was much better than it has been the other times I have tried it, and it stayed good for longer. Before, I have managed to get 1 year old, sometimes older, bags of this coffee. It grows stale in about 1 day after opening the bag, no matter how much I push the air out. Same thing goes for Illy in cans.
That is why I think that a 250g or 500g bag for storing the coffee once you have it in your kitchen is not necessarily better than a hopper - once you have opened it, and especially if you open it often, say 5-6 times or more, which is normal for people that only fill the hopper up with enough for one or two doubles. |
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‹• Bezzera B3000AL • Cona C size • Aeropress • Vev moka • Bialetti Brikka • Cezve • Handpresso Wild • Bacchi Espresso • Arrarex Caravel •
• Anfim KS Self • broken Cimbali Max • OE Pharos •
• oven • hot air gun • Behmor •›
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Olings
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Post subject:
Posted: Jan 23, 2009 - 09:01 PM
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Joined: Jan 06, 2005
Posts: 371
Location: Oslo, Norway
Status: Offline
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Well if you buy old coffee that has been kept artificially kept "fresh" for 1 YEAR (!) or more it will definitely become stale the second you open it like all mummys would.  Even Dr. Frankenstein couldn't bring those beans back to life.
However if we're discussing smaller scale roasters, like where I work for instance, coffee this old is never sold anyway.
But maybe you should patent your idea... A door at the chute that opens when you flick the switch and closes when you turn it off creating a seal in that end, and a lid with a vacuum pump capability. Come to think of it maybe I should patent this myself. 
You read it here first guys and gals. Now I'm doing the wishful thinking hoping noone has had this idea before.
Ola |
_________________
La Marzocco GS3, Compak K10, Dualit grinder, Turkish coffee maker (Ibrik) and grinder, Eva Solo coffee maker, French press, Aeropress.
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zix
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Post subject:
Posted: Jan 23, 2009 - 09:26 PM
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Joined: Mar 24, 2004
Posts: 1312
Location: Partille/Göteborg, Sweden
Status: Offline
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To be honest, superstore beans is not my favourite merchandise.
I usually roast at home, or when I am out of green beans, try to get some from da Matteo (I am sure you know about them, they are on my way home if I have time to go through the city) - but failing those, I sometimes end up at the local ICA or something like that. daMatteo bags are always very fresh.
However, I find it has been a good experience buying that old coffee, since this is what commercial roasters (the BIG ones, of course) tell us is fresh enough. And it usually is OK - but no longer than for a day, in the case of many coffees it only lasts for the first cup or so. Come on, you must have bought at least one can of Illy at one time or another, and experienced the superfast staling process?
But what I am trying to get across here is that the staling process speeds up very much - no matter how fresh the beans are - once you have opened that bag and poured some of the beans out. And that the staling really doesn't stop it for long if you only close the bag again and push the air out of it. Still lots of oxygen left in there.
Maybe it would work with a vacuum sealed hopper - but that is rather hard to do, and not only have I thought of it for a long time before you wrote it here , I also want to say that my point from the beginning was that a fresh coffee doesn't go bad after only 2-3 days in the hopper. A >2 months old coffee, yes, perhaps... but not a 2 weeks old one. |
_________________
‹• Bezzera B3000AL • Cona C size • Aeropress • Vev moka • Bialetti Brikka • Cezve • Handpresso Wild • Bacchi Espresso • Arrarex Caravel •
• Anfim KS Self • broken Cimbali Max • OE Pharos •
• oven • hot air gun • Behmor •›
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