This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
The essential difference between champagne and other wines is that it contains carbon-dioxide gas in solution.
Champagne is made of different grades, representing the first, second, and third expressing of the grape juice respectively. It contains approximately 12 per cent of alcohol, or less.
Good champagne is made as follows: The juice is allowed to ferment for about two weeks, when it is poured into casks and kept for a period varying from two to six months, after which it is bottled and kept from two to nine years in racks arranged to hold the bottles with their mouths down, so that on opening them all sediment which has collected in their necks can be removed or "disgorged." The final process is the addition of sugar-candy sirup dissolved in old wine and white cognac brandy. For the " sec " brand 8 per cent of sirup is added; for other brands varying quantities up to 16 per cent are poured in. A little alcohol, too, may be added, after which the wine is again corked, and left standing.
French champagnes sometimes have liqueurs or cordials added for flavouring, but American champagnes depend solely upon the grape flavour.
Much emphasis is placed on the value of "dry" champagne for invalids, which means that the sugar which it originally contained has disappeared, and hence the wine is less apt to produce flatulent dyspepsia or aggravate conditions in which saccharine food is harmful. True "dryness" is the result of age, and is due to a very slow conversion of sugar into alcohol, such as goes on in port wine which has been kept for several decades, but, as pointed out by Chambers, this process of slow ripening does not remunerate the dealer, so he induces a quicker acetous fermentation by which all the sugar is transformed in a few months, instead of many years, or else he puts but half the quantity of sirup into the wine - 4 instead of 8 per cent. It is champagne manufactured in this manner which is usually shipped out of France for foreign consumption, and hence this wine often has a "dry" taste because it is sour, and not because it is wholly free from sugar. When this is the case, it imparts a bright-red colour to blue litmus, even after the free carbonic acid which it contains has been allowed to escape.
The various brands called "dry," "extra dry," or " sec," "tres sec," usually represent only varying degrees of acidity. "Brut " refers to wines left to undergo natural fermentation.
Undoubtedly one of the reasons why champagne is so exhilarating to many persons is the fact that it is promptly and completely absorbed, even when taken with food. Its effects are therefore suddenly felt by the nervous system.