Improper storage can also cause Champagne to become maderized (i.e., ‘cooked’)—losing its complex character and potentially its effervescence, too.

Wine SpectatorDirect Matches Maderized : Describes the brownish color and slightly sweet, somewhat caramelized and often nutty character found in mature dessert-style wines.

(Maderized is a wine term describing when the wine has been exposed to a long period of oxidation and usually heat. With the exception of Madeira, this can cause the wine to, well, stank).