Why Reheating Coffee Kills Its Flavour

1. Coffee is full of volatile compounds

When you first brew coffee, hundreds of aromatic compounds are released—these are what give coffee its distinct smell and flavor.Reheating (especially in the microwave) breaks these down.

Think of it like reheating a croissant—it’s just not the same.

2. Heat + Oxygen = Oxidation

As brewed coffee sits, it oxidizes (like cut fruit turning brown).

When you reheat it, the process accelerates, creating bitter, stale, even sour flavors.

Reheating = cooking it twice = overkill.

3. Coffee oils go rancid

Coffee contains natural oils that start to break down at high temperatures.

When reheated, these oils can give your coffee a burnt or rubbery aftertaste.

Especially noticeable in darker roasts.

 

4. Microwaves heat unevenly

Unlike stovetops, microwaves heat coffee in bursts and not evenly.Some parts overheat, others stay lukewarm—leading to inconsistent, flat flavour.

Better Alternatives

 

• Use a thermal mug or flask to keep your brew warm longer
• Reheat gently on the stove over low heat (better than nuking it)
• Or… just embrace iced coffee and chill what’s left for later