<p>I am doing my IB Chemistry HL IA on coffee oxidation, and how varying levels of oxidation (or after an amount of time) affects its pH value. I know that over time it will get more acidic, in which the pH value will drop, but I want to know what exactly in coffee causes the oxidation to happen?</p>
<p>I am aware that after brewing the shelf life of the coffee beverages immediately starts to decrease, where the longevity depends on the storage methods of the beans themselves, so what compound reacts with oxygen and loses hydrogens (or electrons)?</p>

CC BY-SA 4.0
2022-06-16T02:39:04.943Z
Welcome to Coffee, does [this](https://coffee.stackexchange.com/q/367) answer your question? [Chemically, what's happening to coffee after it's brewed?](https://coffee.stackexchange.com/q/367)
JJJ
CC BY-SA 4.0
2022-06-16T04:28:51.950Z
@JJJ oh wow thanks. though it does not answer my question to the decree that i was looking for, it does point me in a better direction. tysm!
Frink
CC BY-SA 4.0
2022-06-17T12:39:03.157Z
@Frink, the only response so far is as an ephemeral comment, not as a permanent answer.  If you do find good results from that suggestion (or from elsewhere) and no one else has posted a suitable answer *as an answer*, it would be good if you could post an answer yourself so that in the future, others wondering the same thing will be able to read it.
Ray Butterworth
CC BY-SA 4.0
2022-07-01T17:31:40.560Z
Maybe look at this from a different angle.  Oxygen in the air is what causes the oxidation. What gets oxidized? Probably virtually every one of the very long list of substances comprising coffee. Some are very active and get oxidized easily and quickly; others will take longer. The degree of stale taste will come from the profile of oxidiation--the mix of components that have oxidized a detectable amount, and their degrees of oxidation. But staleness also comes from volatile compounds that mainly affect aroma evaporating, not just oxidation.
fixer1234
<beans>
What exactly in coffee causes oxidation and makes it go stale?
Frink
# What exactly in coffee causes oxidation and makes it go stale?

(Asked by: username_0 on 2022-06-16)

I am doing my IB Chemistry HL IA on coffee oxidation, and how varying levels of oxidation (or after an amount of time) affects its pH value. I know that over time it will get more acidic, in which the pH value will drop, but I want to know what exactly in coffee causes the oxidation to happen?

I am aware that after brewing the shelf life of the coffee beverages immediately starts to decrease, where the longevity depends on the storage methods of the beans themselves, so what compound reacts with oxygen and loses hydrogens (or electrons)?

**Tags:** beans

> **Comments:**
> **username_1**: Welcome to Coffee, does [this](https://coffee.stackexchange.com/q/367) answer your question? [Chemically, what's happening to coffee after it's brewed?](https://coffee.stackexchange.com/q/367)  
> **username_0**: @username_1 oh wow thanks. though it does not answer my question to the decree that i was looking for, it does point me in a better direction. tysm!  
> **username_2**: @username_0, the only response so far is as an ephemeral comment, not as a permanent answer.  If you do find good results from that suggestion (or from elsewhere) and no one else has posted a suitable answer *as an answer*, it would be good if you could post an answer yourself so that in the future, others wondering the same thing will be able to read it.  
> **username_3**: Maybe look at this from a different angle.  Oxygen in the air is what causes the oxidation. What gets oxidized? Probably virtually every one of the very long list of substances comprising coffee. Some are very active and get oxidized easily and quickly; others will take longer. The degree of stale taste will come from the profile of oxidiation--the mix of components that have oxidized a detectable amount, and their degrees of oxidation. But staleness also comes from volatile compounds that mainly affect aroma evaporating, not just oxidation.  

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