Wine

• Wine can be defined as fermented fruit juice. Most wine is fermented grape juice, but almost any fleshy fruit can be fermented.

• Fermenting of sugar in fruits to alcohol occurs naturally, and many animals have enjoyed getting intoxicated on fermented fruit. Thus it is not unlikely that crude wine was humanity’s first experience with alcohol.

• Evidence of fermented grape juice has been seen in 8000 year old pottery shards from China. The ancient Egyptians (5000 years ago) had a well-developed wine production system.

• Wine is mentioned many times in the Bible. Jesus’s first miracle was converting large amounts of water into wine at a wedding feast.

Early History• Many species of grape are found in both the Old

World and the New World.• The species most used for wine making, Vitus

vinifera, was domesticated in western Asia, in the Caucasus Mountains region. It soon spread into the developing civilizations in Mesopotamia.

• The ancient Greeks thought the god Dionysus gave wine to humans, to ease our suffering.– Dionysus was the god of wine, ecstasy, and insanity– Known as Bacchus to the Romans, who celebrated with

orgiastic festivals called Bacchanalia

Native American Grapes• A second species important to wine making is Vitus

labrusca, which is native to North America.– Concord and catawba are varieties of labrusca – When Leif Ericson and the Vikings reached North

America in 1000 AD, they named the place “Vinland” after the labrusca grapes found here. (northern end of Newfoundland)

• In 1860, the European vinyards got infected with an insect, the root aphid, Phylloxera. It is native to North America, and got imported accidentally.– It was found that American (labrusca) grape vines

are resistant to Phylloxera, The Europeans planted it, then grafted vinifera grapes to the labrusca roots.

– This remains the common practice for wine grapes: a hardy, disease-resistant rootstock with good wine grapes grafted on top.

Wine in America• European grapes didn’t grow well in the northeastern

part of the US, where early English settlement occurred. • The Spanish brought grapes to California in 1769, when

Father Junipero Serra founded the chain of missions that became the major cities in California.

• Prohibition (1920-1933) nearly destroyed the American wine industry. A Constitutional amendment was passed banning the manufacture, sale, and transport of alcohol for human consumption. Although this did decrease alcohol consumption, it led to widespread criminal activity, since many people resented the law. Prohibition was repealed by another amendment in 1933.

• California produces the best American wines, and many wine critics rate some of them on par with the best French wines. A blind taste test in 1976, the “Judgment of Paris”, gave California red and white wines top honors when compared to the best French wines.

Wine Growing• Wine grapes like a sunny, dry environment. They

don’t grow well in cooler climates.• Different cultivars like slightly different conditions,

and even minor variations in climate, such as north-facing vs. south-facing slopes, can affect the quality of the wine. – The weather in a given year also has an effect. – Soil conditions also affect wine flavor and quality.

• Wine grapes grow as a vine. They are trained onto trellises and pruned to maximize exposure to the sun.

• It takes about 5 years from planting to full production, and a vine can bear good fruit for 50 years or more.

• It takes about 100 days for the grapes to mature after fertilization. Before maturity, the grapes contain very little sugar: this gives us the expression “sour grapes”.

Extracting the Grape Juice

• Grapes can be harvested mechanically or by hand. Harvest time is set by the winemaker, whose decision is based on sugar content and acidity.

• The juice is extracted from the grapes by pressing them. This was traditionally done by human feet, but a screw press in used today.– The seeds contain bitter compounds, so pressing is done

at relatively low pressures to avoid breaking them.• For white wine, the grape skins are immediately

removed. It is possible to make white wine from red grapes!

• For red wine, the grape skins are allowed to stay with the grape juice during fermentation. The red pigment leaches out of the skins into the juice.

Fermentation• The grape juice is transferred to vats for fermentation.

This process is anaerobic, and the temperature must be controlled because it generates considerable heat.

• It is possible to ferment the grapes using the natural yeast that grows on them. This is the traditional method, but it often led to fermentation failures because other microorganisms would convert the sugars to sour acids (vinegar) instead of alcohol.

• Louis Pasteur, in the 1860’s, first studied wine production from a scientific point of view. He recommended sterilizing the grape juice, then introducing a pure culture of a specific yeast. – Sterilization is done by introducing sulfur dioxide gas. – Different wineries each have their own special yeast.– The yeast is a different strain of Saccharomyces cerevisiae,

also used in producing beer and bread.

Further Steps• Fermentation will continue until all of the sugar has been

converted to alcohol, or until the alcohol concentration reaches about 18%. This takes 2-3 weeks.– However, for sweet wines, the process is stopped before all the sugar is

used up, by adding alcohol to the mixture or by killing the yeast with sulfur dioxide gas.

• A secondary fermentation (aging) then takes place, lasting several months. During this time fine particles settle out of the wine. This process is done under anaerobic conditions. A lot of flavor development occurs during the aging process.

• Before the wine is blended and bottled, a clarifying agent such as gelatin in added to precipitate out any remaining particles. This also reduces tannin content: tannin adds bitterness to the wine. The particles are then removed by filtering.

• Some wines, especially red wines, continue to improve with further aging in the bottle.

Sparkling Wines• Champagne is carbonated wine that is made in the

Champagne district of France. Other sparkling wines are made by the same process, but aren’t technically called champagne.

• The carbonation comes from adding some sugar and fresh yeast to bottled wine. The yeast ferments this extract sugar, and the carbon dioxide gas is trapped in the bottle.

• It is necessary to remove the dead yeast after the fermentation is complete. This is tricky: you can also lose all of the carbon dioxide.

• During this fermentation, the bottle are stored upside down, so the yeast accumulates in the neck. After fermentation is complete, the necks are frozen . The bottle are opened and an icy plug of yeast and wine comes out. A little replacement wine is added, and the bottles are quickly re-sealed.

Distilled Spirits• The alcohol content of beer and wine is limited by the fact

that an alcohol concentration of 18% or more kills the yeast that produces it.

• To produce stronger alcohol, distillation is needed. The principle is that ethanol boils at a temperature lower than water. So, the alcohol boils off, leaving the water behind. You just need to capture the alcohol vapor and condense it.– The first 1% or so of what distills off has headache-inducing

compounds in it, and it is generally discarded. • Distillation was invented by the Arabs around 700 AD.

– The word “alcohol” comes from Arabic: al’kuhul, which refers to kohl, a preparation used to darken the eyes. Alternatively, al’ghoul, which means monster or spirit. This word origin is somewhat debatable.

• Alcohol concentration is measured in proof, where each proof is 1/2 %. So, 80 proof means 40% alcohol. Most distilled spirits are 80-100 proof.

• Alcohol can only be distilled to 95%. It is colorless and tasteless. The color and taste of distilled spirits come from other byproducts of fermentation and aging that remain after distillation.