All alcoholic beverages involve the action of fungi. Most involve the genus Saccharomyces. These yeasts covert six carbon sugars such as glucose to ethanol and carbon dioxide and live under anaerobic conditions. Yeasts can tolerate fairly high concentrations of alcohol (up to about 14-18%) in the medium.
Alcoholic beverages are known from virtually all cultures. These beverages are major social problems, but also sources of nutrition. Many plants have been used to prepare alcoholic beverages.
Plants often store nutrition as starch. Yeasts cannot use starch. The starch is broken down by enzymes in the plant into sugars. The sugars are then converted by the yeasts into ethanol and carbon dioxide.
Alcohol is a lipid and moves freely across membranes in the stomach. Alcohol is broken down in humans, but also affects the neurons and is a non-selective central nervous system depressant.

Wine is fermented fruit juice. The most important fruit is Vitis vinifera(Vitaceae), but any fruit can be used. Mead is made from fermented honey. Yeasts occur on the skins of most fruits and if the fruits are mashed, the sugar-containing juices begin to ferment.
Winemaking probably began as one of the earliest of human enterprises (8000-3000 B.C.). The wine grape was domesticated by at least 4000 B.C. Wine was used for Egyptian worship ceremonies. Wine only became a popular beverage in about 2000-1000 B.C. in Greece. In about 600 B.C., wine growing reached France.
Wine grapes were introduced early into the United States. The Spanish introduced grapes into California in the 1700's. Between 1850 and 1860, the root louse, Phylloxera, was introduced inadvertently from North America into Europe. The insect decimated fields of Vitis vinifera. The problem was solved by making hybrids or grafting European grapes on American grape roots.

Many good quality wines are still made in the same way they have been made for centuries. However, most wines are now made by sophisticated highly controlled processes. Grapes are crushed (still by foot or with crude presses in many parts of the world). The juice is then often treated with sulfur dioxide to kill native yeasts. See the diagram on page 343.
If white wine is to be made, the juice is put into fermentation tanks and the peels and stems re-pressed. If red wine is to be made, the skins are added. Special strains of yeasts are added to the liquid from the grapes. These are often highly guarded trade secrets and proprietary substances. After 8-10 days, the liquid is drawn off and allowed to ferment for another 20 days to one month. Sediment forms. At this point the wine is drawn off and placed in aging tanks. White wines are usually aged from 1 year to 18 months and red wines as long as 5 years.
White wines are generally not too good after 5 years; red wines improve up to 30-40 years. Wine labelling: see page 486.

Champagne and sparkling wines are made by putting the wine into a bottle with a little added sugar. The carbon dioxide produced carbonates the wine. The sediment is removed and the the wine maintained under pressure.
Apples and pears are used to make cider and perry respectively. To make fortified wines, ethanol or distilled beverages such as cognac are added. One group (including port, sherry, and madeira) is made exclusively from grapes, whereas the second group includes aperitif wines and other flavorings (such as Dubonnet and vermouth).
As many as 40 million metric tons of grapes are produced per year. The major wine making countries are the former USSR, France, Italy, USA, Spain, Germany, Australia, Argentina, Chile and South Africa. Consumption of wine in France is about 30 gal per person per year and about 2 in the U.S.

Wine aging

Beer, Ale, and Stout
Beer making goes back at least 6000 years. The Sumerians had records about brewing of beer. Early brewing is intimately linked with bread making. This is one way of making the grains more edible for man. Although the Egyptians used wine for religious ceremonies, they commonly drank beer.
Yeasts were developed and saved to give better qualities of beer. Today beer making is also a quite sophisticated process. The three main ingredients are barley malt, hops and water. As much as 7.5 X 109 liters of beer are made per year (2 X 109 gallons).

Malt is a sprouted grain that is dried. Barley ( Hordeum vulgare, Poaceae or Gramineae), is preferred for several reasons. The husks stay on the kernels and add some of the flavor. Also, barley contains higher concentrations of the enzymes needed for onverting starches into sugars.
The grain is steeped in water and allowed to sit where it is warm until germination begins. The grain synthesizes hydrolytic enzymes and converts starch to sugar. The cell walls of the endosperm break down. The mixture is then dried at 130 to 200 C.

Hops (Humulus lupulus,Cannabaceae) were only added to beer after about the year 700 A.D. The English only started adding them in about the 1500's. Sometimes other plants were added for flavoring before that time. Hops not only add flavor but help to coagulate and precipitate proteins.
The female inflorescences are used. They contain a glandular exudate with the flavor properties.

Hops in field

Adjuncts are unmalted grains that are added. Barley, rice, wheat, or corn grits are often used. In other countries potatoes or cassava may be used. They are commonly used in the U.S., but not often in Europe. They are less expensive than barley malt. Corn and rice are both precooked before being added.

The brewing process
See the diagram on page 493. The process is now highly mechanised. The malt is extracted at 68-73 °C for 2-6 hours, a process called mashing. During mashing, the enzymes diffuse into the solution and break down the starch in the malt and the adjuncts. Proteins are degraded into amino acids. The resulting liquid, called wort, contains sugars, some starches, proteins and amino acids, among other components. The spent malt and adjuncts often are used for cattle feed.
Hops are then added and the liquid boiled. This boiling step does several things. The yeasts present are killed.
Enzymes are denatured. Compounds in the hops are converted into the compounds that give beer its bitter taste. The hops are then removed. The liquid is pumped to fermentation tanks and yeast is added. Saccharomyces cerevisiaeis a top fermenting yeast and S. uuvarumis a bottom fermenting yeast. The latter is used to make ales and lager beers.
The carbon dioxide is allowed to escape and is a major byproduct of brewing. The mixture is allowed to ferment for 7-12 days at cool temperatures. The resultant liquid is tranferred and allowed to age for 2-3 weeks. Proteins precipitate out and some other chemical modifications take place.
In the U.S., most of the beers are pasteurized or micropore filtered to remove yeasts. The beer is usually carbonated.

Sake is made from rice and is a traditional beverage in Japan. It is a fermented grain beverage. Aspergillus oryzaeis used to convert the starch to sugar and then yeast added. Both are involved in the fermentation process. The mixture is fermented for about 25 days. The alcohol content is about 18-19%. The beverage is allowed to mature for about 40 days. It is consumed before 1 year.

Pulque is made by fermenting the juice of Agave species, especially A. americana. Pulque made from Agave tequilana is distilled to produce tequila.

Chicha is made by chewing cassava or corn and spitting the materials into a tank or container. The mixture is then allowed to ferment. The saliva serves as a source of amylase to break down starches. This beverage is found in many areas of western South America.

Other alcoholic beverages
Kvass is made from fermented bread, barley or rye. It is sometimes peppermint flavored and is popular in the former Soviet Union. Sorgo is made from fermented sorghum in Africa.

Distillation involves converting components to the vapor phase and then recondensing them. The Arabs probably discovered the process. They distilled perfume components and other mixtures of fermented materials. Many of these were prepared for medicinals.
By the 15th century, the English and Scots had begun distilling barley beer and, in the 16th century, cognac was prepared in France. Whiskeys were made in a similar way. Once distilled, the mixture is diluted back to about 50% alcohol in general. Whiskeys are aged in barrels. The inside of these barrels is often charred. The barrel provides some of the flavoring materials.
Scotch whiskeys have a characteristic taste because of the smoking process (over peat) used to dry the malt.
Bourbon whiskey is made from corn as the primary grain (Zea mays, Poaceae) and was developed by the early Scottish (many of whom are called Scoch-Irish) immigrants in Pennsylvania. It is aged for at least two years in new, charred oak barrels.
Whiskey aging in barrels

Rye whiskey contains at least 51% rye and also must be aged at least two years. Irish whiskey contains barley malt (sometimes wheat and rye added) and differs mostly from Scotch in that the malt is not dried with peat.
Gin and Vodka are distilled to a high percentage of alcohol and in the case of gin, Juniperus communis, Cupressaceae, "berries" are added. These beverages can be distilled from just about any fermented mixture including potatoes, grains, etc.
Rum is made from fermented molasses or sugar cane juice.
Tequila and Mescal are distilled from pulque made from various Agave species.

Brandies are distilled wines. The most famous come from France. Cognac is one type. The fermented juices of many other fruits are also distilled. Liquers differ from brandy in that various flavoring agents are added. They have sugar and syrups added.

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Revised April 2005

© David S. Seigler, Integrative Biology 363, Plants and Their Uses, Department of Plant Biology, 265 Morrill Hall, 505 S. Goodwin Ave., University of Illinois, Urbana, Illinois 61801, USA. 217-333-7577.