Since I am the only coffee drinker in the house, I started making coffee a quart at a time and saving it in a mason jar in the fridge. I discovered this interesting thing. Starting with about the 3rd opening of the jar, when I warm up the coffee in the microwave and then add a spoon of sugar, a fine lace of foam rises to the surface, giving the coffee the texture of crema coffee. I assume something in the air (nitrogen?) is being dissolved into the chilled coffee and then brought out of solution.
Further, I think the coffee tastes smoother after it has aged a couple days. I don't have a great palate, but I suspect something is going on that is analogous to the binding of tannins in wine, but I have no idea.
Can anyone shed some light on this?