Ryder wrote: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.
I'm brand new to this forum, and I joined just so I could say something on this subject. I may know very little about roasting coffee, but I am a biochemist and I know a thing or two about acid/base chemistry and organic chemistry.
I agree with bigbells who said the original poster is missing the point about CO2. CO2 bubbling up when water is first added is a sign of recent roasting, but it doesn't act as much of a barrier to hot water in extracting the flavor components from coffee. I also don't think it has anything directly to do with the presence or absence of flavor.
The real barrier to extracting flavor from the grounds is that coffee's flavor oils are poorly soluble in water. It takes heat and time to extract these oily compounds from the grounds. They don't really dissolve so much as get suspended in hot water. You can see those shimmering oils floating on top of the coffee in the cup. When coffee is fresh, the grounds clump up when you first add water because there are enough flavor oils in the grounds to keep out the water. Extraction works better if you break up the clumps so the grounds can get wet. That's probably also why we need hot water, at about 205°.
Even before I roasted coffee, I knew that while making Melitta drip coffee I had to wet the grounds with some hot water and wait a minute or so before adding the rest of the water to get more flavor. And this was with beans that were not nearly so fresh. They never produced the CO2 foam that I can see now when I first add water.
I'm not at all sure what's going on with the rest time after roasting. The Kenyan Nyeri AA Gatomboya I recently had (its already gone
) took 3 or 4 days for its full flavor to develop. Why is that? I did notice that during the first day or two after roasting, very little gas was filling the bag, but by the 3rd day after roasting the bags became noticeably inflated each day. I'm guessing that when the gas comes out of the beans its a sign that they are ready to brew, but I wonder if it has anything directly to do with the flavor.
Thanks for reading my first and somewhat long post here.