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Posted: 3/17/2002 7:46:53 PM EDT
Link Posted: 3/18/2002 1:59:12 AM EDT
Originally Posted By DoubleFeed: 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.
Link Posted: 3/18/2002 1:30:40 PM EDT
I don't know about eggs or egg shells in coffee, but a pinch of salt will do wonders for the taste. That, or you could try washing the pot (and your cup) more often than once a year.
Link Posted: 3/18/2002 1:55:05 PM EDT
Best thing to do with a bad pot of coffee is use it to rejuvenate the color of your khakis and make a fresh pot for dinking. I suspect the chemical reaction to which you allude is similar to burning and results in the formation of yukky tasting hydrocarbons.
Link Posted: 3/18/2002 2:02:35 PM EDT
Pinch of Arm and Hammer soda, neutralizes the acid every time!
Link Posted: 3/18/2002 2:30:29 PM EDT
Hmmmmm... hydrocarbons
Link Posted: 3/18/2002 2:39:30 PM EDT
Coffee as we know it starts out as partially pyrolyzed (that's burned for you Aggies, much like your old bonfire)seeds. Why the beans don't burn is lack of oxygen. Fresh-made coffee doesn't have much dissolved oxygen in it since its quite hot. Letting it sit at elevated temps in an open pot exposes the surface to oxygen where the aromatics that give it good flavor evaporate and the oxygen polymerizes the phenols and tannins into bitter nasty stuff. This can happen without serious evaporation/concentration making a light pot of coffee get muddy dark and completely nasty. Its a chemical change, just as you have asked and its oxidation. Keeping it in a closed container like a Thermos or closed Dewar flask keeps it fresh as the oxygen cannot get to it.
Link Posted: 3/18/2002 2:43:04 PM EDT
Biological systems suchs as coffee beans contain thousands upon thousands of substances, so I couldn't tell you which ones are responsible. I would guess that it is some type of oxidation reaction. The air we breath is a relatively fierce substance. Cold water can contain more dissolved gases than hot water. My guess would be that as the coffee cools or sits around too long while hot, oxygen works it's way in and oxidizes certain substances. Heat, oxygen and water are a combination that degrade many organic molecules. Frequently carboxylic acids are generated under these conditions.
Link Posted: 3/18/2002 3:40:53 PM EDT
This might be morbid. When we have to pronounce a DOA. One that has been laying in a house or Apt for a couple of days. We burn coffee or coffee grounds. It takes that smell out of the air.
Link Posted: 3/18/2002 3:51:47 PM EDT
Coffee that's brewed and kept too hot gets oils out of the beans that have a bitter taste. This was told me by a guy that's a high-dollar chef type cook. He makes good coffee. I brew and hold mine cooler and that seems to work for me.
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