Is it bean abuse to rest post-roast coffee by airing it?

[FincaFine]

CO2 is a good guess given all the talk about CO2 but it would be nice to know for sure. I think if you used FoodSaver bags or similar and vacuumed them tight there would be little swelling. These are things that we should be trying and sharing. The Mason jars showed little increase in pressure (i.e. were no less easy to open after three days - had to use the blunt end of a beer opener as always). Most importantly they did not explode or have bludging lids as some warn about for simply making the seal air tight but with air inside.

I also found that you can vacuum out commercial bags with one way values using the re-sealable vacuum bag adapter. (Of course, think about which direction the valve is meant to operate). But they are lousy at holding the vacuum, so those "air tight" promises about the bag are as silly as their mainly overroasted coffee. To be honest the FoodSave resealable bags also have very mixed reliability.

I have a date this week with a man in a mask using sharp objects ruthlessly assisted by a similarly masked team to keep me from moving in the OR - trust me, you don't want to mess with gang unless you have to! By the time I get home my SM green bean refills should have arrived (currently I am in my snobby Guatemala Finca phase because I had an opportunity to tour one recently). The plan is to prepare and seal three roasts to be opened simultaneously when the last one is ready. The youngest will be at three days, second one at six days, and oldest at nine (or twelve) days. The test will be judgement by pure amateurs as to the freshness and personal preference. I figure even cowboys can tell if something is truly off. If no obvious problems, I leave it to the experts to try it and to render their opinions. [Of course in home roasting,we are the final mugwumps in the house who get to say what we like!]

[w0fms]

I think some oxidation actually improves the flavor of some coffees. I don't like anything that rests less than 48 hours, and 72 hrs to one week is ideal for most, IMHO.

As for CO2 outgassing-- that depends a lot on roast level (darker seems to do a little more) but more so on the origin of the beans. I use Mason Jars, leave the lids loose for 24 hrs and then seal 'em down. Some origins (like Costa Rica) never pressurize the jars. Others (like many Africans) will "pop" like opening up a canned vegetable, but pressure and not vaccuum.

I don't think a seal-a-meal would make enough of a difference to justify the cost, but that's just me.

Roast and don't let the stuff go much more than a week if you can avoid it and enjoy.

Fred

[FincaFine]

What happens when you just vacuum seal it up immediately? I am also curious about preserving because I options: I like being able to roast more at once, l like being able to give a roast away as gift, or having more than one choice on hand. I don't particularly see being forced to roast more often as a desirable goal in itself.

[FincaFine]

The figure of 100+ psi comes from chemist Bob Barazza's statement that the internal CO2 in freshly roasted coffee is stored at approximately 130 psi. That statement, in turn, comes from the HomeBarista forum referenced in the "why rest beans at all" thread. My understanding of those statements is that this CO2 is not created by the existence of oxygen in the post-roast environment, but is trapped within the bean during the roasting process.

No idea the about the validity of that claim. It sounds a bit suspicious. One might think at 130psi there would be a third crack that would sound more like a sonic boom. The Intertubes are full of marvelous claims of uncertain truth, like the one I made, but I labelled mine for discussion! So I leave it to the 130psi crowd to back their claim up with evidence. But that should not stop the rest of us from experimenting.

[martin]

Nah, 130 psi is on the same order as the [mostly] steam pressure that drives bean expansion. At FIRST crack, internal temperatures are around 356°F (and still rising), which matches steam pressures of 130 psi and up. (steam table says 145 psi absolute, but the lower gauge pressure is, as usual, the more relevant number) Any internal voids that are left unruptured by steam during roasting shouldn't have any trouble holding 100+ psi of other gasses that develop during or after roating.

And I have some anecdotal evidence about the value of [some] oxygen to post roast development. By chance, I've had some recent roasts that both had a pretty clear (and short) peak, and which I didn't give end up sharing with friends so that I had two canning jars sitting next to each other on the same shelf. The jars that were opened for early use (in both cases I hadn't been roasting ahead, and was consuming the coffee before it peaked) peaked, then when I opened the second jars they were, despite longer total time of rest, a little before their peaks. It needs to be added that I close the jars half an hour to an hour after roasting, and didn't open the second jars further than enough to "burp" the gas (not a great deal) every couple days; the first jars were briefly opened once or twice a day to weight out a dose for brewing.

Oh - also, the first jars sometimes had an obvious "more gas than usual" day, generally around three days after roasting. The second jars would do that a day or two after they were opened for dosing (viz., after significant oxygen was allowed to sneak in).

[w0fms]

135 PSI is the magic 9 bars of pressure you use for Espresso! So maybe there is something to it?

Fred

[ChemEng]

Here's 2 cents from an acknowledged real newbie (I have only roasted a few batches and have a looooong way to go before I know 1/10th of what you guys do); however, I am a chemical engineer by trade (not boasting, just a bit of background info as I am fairly new to this forum):

As I understand things, after roasting, the beans produce oils (some more than others, depending on roast level and bean type), but some of these oils are volatile (which is why we smell the wonderful smells that we do). It would seem to me that vacuum packing roasted coffee would force more of these volatile oils to volatilize under that low pressure, thus removing some of the things we are actually trying to preserve (thus not as flavorful or good smelling cups). Therefore vacuum packing would seem to be a bad idea to me.

As for CO2, I may have access to a CO2 meter at work--I'll try to borrow it and see if I can provide some concentration data inside a one-way valve bag over the course of aging my next roast (whenever that will be!). Although I don't drink coffee, this is one of the reasons I got into this hobby--there is so much science behind it.

Robert

[FincaFine]

Most excellent idea. So you are speculating (all of us are) that oxygen maybe necessary for the early development of desirable volatiles. It would be good to know if CO2 really is thrown off by vacuum sealed coffee. Red Barn Roasters in Massachusetts claims to seal with nitrogen which other than gas pressure levels would have the same kind of non-oxidizing properties. Of course, vacuum sealing after the initial period is not controversial.

I wonder if there might be an equivalent to letting wine breath and in particular will those volatiles still appear after first exposure to air allowing longer storage time vacuum sealed but requiring some kind of open air resting time later on after opening?

BTW, you have a great name.

---Robert
"No NOT BOB - ROBERT, bob is what certain kinds of cats and boxers do."

[bigbells]

"No NOT BOB - ROBERT, bob is what certain kinds of cats and boxers do."

Don't forget the device often attached to fishing lines. I delivered mail for several years to a family that named one of their sons Robert and another of their sons Bobby. The mother did not know that one is generally considered a nickname for the other. This created quite a problem for the USPS when Bobby moved out and submitted an individual change of address form. The automated software used by the USPS is programmed to read both names as the same.

[ChemEng]

So you are speculating (all of us are) that oxygen maybe necessary for the early development of desirable volatiles.

Unfortunately, I may not have been as clear as I could have been. I am not saying oxygen is necessary for development of volatiles--in fact just the opposite. From all that I have read (mostly books, this forum thing is kind of new to me), the volatiles form during and continue to form after roasting, but oxygen is their enemy-oxidation will break them down.

As stated earlier in this topic, the CO2 given off will purge and dilute the O2 in the storage container (which is why I believe in the one way valve bags/containers--it gives the purged gasses somewhere to go, but keeping the enemy, O2, out). Purging oxygen from the storage container is a good thing (sorry Martha!)--in fact before I even got going in this I contemplated putting a small amount of dry ice into the storage vessel to displace the oxygen (I think i have changed my position on that though, due to the moisture condensing).

Also regarding my earlier post, while it may not controversial , I am of the belief that putting things under a negative pressure will cause loss of volatiles, thus degrading the coffee. After giving it more thought after I logged off last night ( ) I do however acknowledge that the amount of volatiles lost may not be that noticeable in a cup (or pot) of coffee. However, my preference is no vacuum packing--YMMV.

I may have been wrong about the CO2 meter-I may be able to measure oxygen concentration though.

And thank you for understanding about the Bob/Bobby thing--

Robert