Why Rest Beans at all?

[Ryder]

We're told that the beans release CO2, which is all fine and dandy... but CO2 shouldn't be an issue... it's colorless and odorless... is this just a myth?

I am sure *something* is happening to the "bean" overnight... but the release of CO2 should not be an issue of any kind. We have CO2 in our throats, mouths and sinuses constantly that we produce ourselves.

Sorry to be a skeptic here, and obviously taste is an individual preference, but I'd really like to understand the chemistry of the "rest" a bit better.

Ryder

[bigbells]

We're told that the beans release CO2, which is all fine and dandy... but CO2 shouldn't be an issue... it's colorless and odorless... is this just a myth?

I am sure *something* is happening to the "bean" overnight... but the release of CO2 should not be an issue of any kind. We have CO2 in our throats, mouths and sinuses constantly that we produce ourselves.

Sorry to be a skeptic here, and obviously taste is an individual preference, but I'd really like to understand the chemistry of the "rest" a bit better.

Ryder

I think you're missing the point. I haven't ever heard anyone advise against unrested beans on the grounds that the CO2 represents some kind of health hazard. That isn't the reason for resting the beans; it's just one of the things that happens as the beans rest. The reason for various periods of recommended rest is for the flavor of the resultant coffee, which changes depending on the amount of rest.

[Weyesa]

I've read that the issue is that the CO2 interferes with extraction-- acts as a barrier between the bean and the water.

This was the first article I found on the topic, so I'm not selling at as the authority, just one guy who says something I understood to be true from other research.

[Weyesa]

Here is a lively debate on the subject as it relates to espresso. Most people say resting is more important for espresso.

[BoldJava]

I've read that the issue is that the CO2 interferes with extraction-- acts as a barrier between the bean and the water.

This was the first article I found on the topic, so I'm not selling at as the authority, just one guy who says something I understood to be true from other research.

Yep, the CO2 acts as a barrier/shield to extraction. Once the CO2 is dissipated, the water can better extract the coffee.

[bigbells]

Interesting links, Weyesa, regarding the effects of released CO2 on the ability of the coffee to be extracted as desired. I had no clue that this was part of the reasoning for resting a roast; I thought that the only reason for rest was to let flavors develop, and that CO2 release was merely an innocent byproduct that was caught up in the process.

One thing I'm pretty sure of, though, is that too little rest is preferable to too much rest. I got too far ahead in my roasting, then kept picking my latest roasts when making pots of coffee, which resulted in having some jars of roasted beans that moved deeper and deeper into the cupboard as they got further and further beyond their dates of roast. I'm committed to using them up before I roast again, and still have a couple days worth left to use. About 7 oz left, 4 oz of which were roasted 41 days ago and 3 oz of which were roasted 16 days ago. Both are very significantly less exciting than they were within the first several days.

[Ryder]

We're told that the beans release CO2, which is all fine and dandy... but CO2 shouldn't be an issue... it's colorless and odorless... is this just a myth?

I am sure *something* is happening to the "bean" overnight... but the release of CO2 should not be an issue of any kind. We have CO2 in our throats, mouths and sinuses constantly that we produce ourselves.

Sorry to be a skeptic here, and obviously taste is an individual preference, but I'd really like to understand the chemistry of the "rest" a bit better.

Ryder

I think you're missing the point. I haven't ever heard anyone advise against unrested beans on the grounds that the CO2 represents some kind of health hazard. That isn't the reason for resting the beans; it's just one of the things that happens as the beans rest. The reason for various periods of recommended rest is for the flavor of the resultant coffee, which changes depending on the amount of rest.

I never mention health. I am saying that CO2 is a natural part of US, so it's obviously OK... and as such, we can't detect it.

Regards,

R

[Ryder]

I've read that the issue is that the CO2 interferes with extraction-- acts as a barrier between the bean and the water.

This was the first article I found on the topic, so I'm not selling at as the authority, just one guy who says something I understood to be true from other research.

Interesting... I'll look into it.... but liquid displaces gas like nobodies business (that is what is happening when water boils). It moves away so fast... liquid goes through gas like a hot knife through butter.

Thanks for the link... I'll read up!

Ryder

[Ryder]

I've read that the issue is that the CO2 interferes with extraction-- acts as a barrier between the bean and the water.

Yep, the CO2 acts as a barrier/shield to extraction. Once the CO2 is dissipated, the water can better extract the coffee.

Hi BoldJava! See, the thing I think I hear people saying is that when CO2 leaves, then the barrier leaves... and that can't be true. If you have concentrations of CO2, and you allow them to evolve... all they are doing is obeying the partial pressure law... and equalizing to normal atmosphere... so CO2 leaves... and nitrogen and oxygen *replace it*. So there are STILL gasses in there (if not, then what, exactly, is?).

When the hot water hits the coffee... and heated gasses expand and leave the coffee... it shouldn't matter what is escaping... nitrogen, oxygen, moisture, CO2.... they are all gasses... all escaping.... all creating a (very) temporary barrier. Exchanging CO2 for something different should make zero difference here.

What this means to me is that any benefit of resting to flavor (if there is one... and I believe there is because so many detect it) must come from a change in the quality of the bean itself over the rest period... and not really be a part of gas escape during brew... as that will always happen.

It has to be the bean changing in some manner, the way I see it. Certainly it is oxidizing for all normal container storage... is a little oxidation good?

Ryder

[bigbells]

Gosh, Ryder, next you'll be telling us that little microparticles of aspirin don't have individual GPS navigation to guide them directly to the site of the pain. I'll admit you've done a good job of questioning the CO2 "barrier" theory but I have no clue as to what the explanation is, if any. I was kind of assuming that the CO2 was replaced by coffee when it departed, sort of collapsing around the vacuum left behind. That may be a ridiculous theory, I just don't know.