<p>Caffeine has a very very low vapor pressure 9.0X10-7 mm Hg at 25 deg C.  <a href="https://pubchem.ncbi.nlm.nih.gov/compound/caffeine#section=Melting-Point" rel="noreferrer">Source</a>  </p>

<p>Almost none would evaporate.  </p>

CC BY-SA 3.0
2017-01-23T06:14:10.847Z
Did you consider oxidation, too? I checked, but cannot find a nice source if it oxidizes in atmosphere under room conditions.
MTSan
CC BY-SA 3.0
2017-02-20T11:51:51.477Z
It doesn't seem to be readily oxidizable either, so I doubt you would lose much/any.
comeauch
CC BY-SA 3.0
2017-02-22T19:11:30.803Z
There are several bacterial species that can/will live on caffeine and storing grounds in an "open container" could lead to contamination from such.
Suspended User
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2017-03-01T08:50:35.300Z
@Chris_in_AK If you have more details, you're welcome to expand in an answer.
Ludwik
CC BY-SA 3.0
2017-01-22T18:46:29.680Z
2017-01-22T18:46:29.680Z
paparazzo
<p>What I know is that, for the best taste, one should grind the coffee right before brewing it. Storing ground coffee makes it lose part of its taste, even if there are ways to counteract that effect. However, assume I ground up some coffee and left it in an open conatiner for several weeks. Would the coffee lose any <strong>caffeine</strong>, i.e. would I feel the effects of the coffee less than if I had brewed it directly after grinding?</p>

<p>If yes, what mechanisms are responsible for this and how does the caffeine leave the coffee?</p>

<caffeine><ground-coffee><storage><aroma>
Does ground coffee lose caffeine like it loses aroma?
Ludwik
# Does ground coffee lose caffeine like it loses aroma?

(Asked by: username_0 on 2017-01-22)

What I know is that, for the best taste, one should grind the coffee right before brewing it. Storing ground coffee makes it lose part of its taste, even if there are ways to counteract that effect. However, assume I ground up some coffee and left it in an open conatiner for several weeks. Would the coffee lose any **caffeine**, i.e. would I feel the effects of the coffee less than if I had brewed it directly after grinding?

If yes, what mechanisms are responsible for this and how does the caffeine leave the coffee?

**Tags:** caffeine, ground-coffee, storage, aroma


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## 1 answers

### Answer by username_1 on 2017-01-22. Score: 7 | Accepted answer

Caffeine has a very very low vapor pressure 9.0X10-7 mm Hg at 25 deg C. [Source](https://pubchem.ncbi.nlm.nih.gov/compound/caffeine#section=Melting-Point)

Almost none would evaporate.

> **Comments:**
> **username_2**: Did you consider oxidation, too? I checked, but cannot find a nice source if it oxidizes in atmosphere under room conditions.  
> **username_3**: It doesn't seem to be readily oxidizable either, so I doubt you would lose much/any.  
> **username_4**: There are several bacterial species that can/will live on caffeine and storing grounds in an "open container" could lead to contamination from such.  
> **username_0**: @Chris_in_AK If you have more details, you're welcome to expand in an answer.  

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