Chemistry of alcoholic beverages

Other Alcohols.
Methanol occurs in wines at a very low level (38– 200 mg/l), but much more is present in the fermentation of pomace as a product of pectin hydrolysis. Brandy distilled from pomace often contains 1–2% methanol. Higher alcohols in wine are propyl, butyl and amyl alcohols which, together, constitute 99% of the wine fusel oil. Hexyl, heptyl and nonyl alcohol and other alcohols including 2-phenylethanol (up to 150 mg/l) are present in small amounts. The average butylene glycol (2,3- butanediol) content is 0.4–0.7 g/l and is derived from diacetyl by yeast fermentation. Glycerol, 6– 10 g/l, originates from sugars and gives wine its body and round taste. Added glycerol can be revealed by the determination of the glycerol factor (GF):

The natural variation range of GF in wines, as long as they have not been produced from noble rot material, lies between 8 and 10. Values above 12 indicate an additive. Low amounts of additive cannot be safely detected using the GF. More suitable is then the use of GC-MS to test the wine for the by-products of the technical synthesis of glycerol, e. g. 3-methoxypropanediol or cyclic diglycerols. Sorbitol is found in very low amounts. D-Mannitol is not present in healthy wines, but is present in spoiled, bacteria-infected wines at levels up to 35 g/l.

Liquor from Wine, Fruit, Cereals and Sugar Cane.
These beverages have a distinct taste and odor and contain at least 38% ethanol by volume. They are called natural, genuine or true liquors. The distillate resulting from a single distillation has a low alcohol content and often contains the specific odor and taste components of the starting material (harsh raw grain or harsh raw juniper liquor-gin). In the production of liquor, the ultimate aim is to collect most of the desirable, specific fragrance and aroma substances (esters, essential oils) or to develop them (hydrogen cyanide, fermentation products, yeast oil) by using suitable mashing, fermentation and distillation processes. The freshly distilled liquor has a hard, burning taste and unpleasant odor. It is improved by aging, which gives it a new, desirable aroma and flavor. Therefore, aging of liquor is of the utmost importance.