Do not pre-heat your coffee
Do not re hot your coffee
it always happened to me that I preheated my coffee when I had already brewed it and then in the microwave or again in the kitchen because this is very bad, I read an article and draw my conclusions that I will not do it anymore.
What happens if I preheat it?
The pH of the coffee is 5.3 or 5. 5 similar to that of a fruit in this case the mandarin is not harmful.
When reheating the coffee the pH drops to about 2.3
like the one of a lemon half cool this if it is in a kitchen, now if it is in microwave lowers the pH of the coffee to 1.2 and 1.5
as well as a battery.
Note @karchady: I think we should take only the coffee that we paste or that we made in greca the first and no longer to have a coffee that would not have the same ph.