Quoted:
Exactly what is the heat induced chemical change, that turns good coffee into bitter battery acid coffee?
Just figured I would ask. Nobody else knows. [:D]
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I don't know, but it can be very powerful. I've had coffee I just could't keep on my tongue.
The bizarre thing is, I believe it came out when McDonalds was getting sued by the old lady that they kept their cofee extra hot to keep it from going bad. Or maybe whatever gives it the bitter taste gets distilled off at the higher temperatures.
What I've always wondered about is what's the deal with putting egg in the coffee. One reason seems to be that's how you can make it in a pot and keep the grounds from being poured into your cup - the egg cooks in the bottom of the pot and retains the grounds.
But my friend was in the Navy and said that he saw egg shells in the basket in the top of the pot. His idea was that it might do something for the taste.