cafeIKE wrote:Let's try a famous AndyS thought experiment: Roast some coffee. Split the roast in to equal parts. Grind one part as for drip. Seal both halves for a couple of weeks. Would you expect a markedly different gas and aromatic volume? Yes, if there was a lot of CO2 and aromatics physically trapped in the bean released by grinding. : No, it's likely that CO2 and aromatic compounds are by-products of the staling process.
I don't know for certain, do you? But my money is on NO.
Hmmm...further evidence of the futility of thought experiments?
I don't understand the point you're trying to make, but yes, there is a LOT of CO2 and a lot of aromatics physically trapped in freshly roasted beans. They eventually make their way out, whether the beans are ground or not.
Illy, Espresso Coffee, 2nd edition, p.236 wrote:Carbon dioxide formed during roasting is trapped in the cellular structure of the bean and is only released over a period of weeks following roasting, resulting in a 1.5-1.7% weight loss....The driving force at the basis of carbon dioxide and volatile release from roasted coffee is given by a diffusion flow due both to concentration and pressure gradients....The few data available about volatile partition kinetics from roasted coffee packed in air indicate that the rates of CO2 and volatiles release are of the same magnitude.
It is possible that some of the CO2 released in staling is newly formed as the result of chemical reactions, but the vast majority has already been produced in the roasting process. As far as the aromatic compounds are concerned, there are hundreds of desirable aromatic compounds formed during roasting (according to Illy). In the aging process, many of these are gradually oxidized to form characteristic stale coffee aromas.
Interestingly, in looking through Illy's book to find the section quoted above, I found a paragraph that speaks directly to the effect of temperature on CO2 and volatiles release:
Illy, 2nd edition, p. 238 wrote:in the experimental conditions adopted, for any 10C increase, the rate of volatile release increased 1.5-fold
If it's true that the rate of chemical staling reactions doubles with every 10C, and the rate of CO2/volatiles release increases 1.5x with every 10C, then your original assertion is, again, an oversimplification:
Ike wrote:coffee staling and freezing is simple chemistry :
- Changing the temperature from +20°C to -20°C slows staling by a factor of 16. In laymans terms, two weeks in your typical refrigerator freezer equates to one day at room temperature.
- Changing the temperature from +20°C to -30°C slows staling by a factor of 32. In laymans terms, one month in your typical chest deep freeze equates to one day at room temperature.