Grape

• 1. Introduction

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  A grape is a berry, technically speaking, produced by the deciduous woody vines of the plant genus Vitis and gathered in clusters. In Armenia, archaeologists found the Areni-1 winery, the oldest known winery in the world, dating back to around 4000 BC. Humans have been cultivating grapes for roughly 8,000 years, eating them fresh, drying them into raisins, currants, and sultanas, and pressing them into wine, juice, vinegar, jam, and oil. Yet the fruit itself is a small chemical factory, changing color, sugar, and acidity as it ripens, and carrying compounds in its skin and seeds that researchers are still cataloguing today. How did a wild woody vine become one of humanity's oldest cultivated crops, and what exactly happens inside a grape as it turns from hard and green to sweet and ripe?

• 2. Wine Travels West

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  Cultivation of the grape began in the Middle East between 6,000 and 8,000 years ago, and yeast, one of the earliest microorganisms humans domesticated, occurs naturally on grape skins, which is how alcoholic drinks such as wine were likely discovered. The earliest archeological evidence for wine-making holding a dominant place in human culture dates to 8,000 years ago in Georgia, while the Areni-1 winery in Armenia, dated to around 4000 BC, is the oldest known winery found anywhere. By the 9th century AD, the city of Shiraz was known for producing some of the finest wines in the Middle East, and it has been proposed that Syrah red wine takes its name from Shiraz, a city in Persia where the grape was used to make Shirazi wine. Ancient Egyptian hieroglyphics record the cultivation of purple grapes, and the ancient Greeks, Cypriots, Phoenicians, and Romans are all attested growing purple grapes for eating and for wine, spreading the practice into Europe and North Africa. In 2005 a team of archaeologists concluded that Chalcolithic wine jars discovered in Cyprus in the 1930s dated back to 3500 BC, making them the oldest of their kind in the world, and Commandaria, a sweet dessert wine still made in Cyprus, is the oldest continuously manufactured wine in the world, with origins reaching back to 2000 BC. Native grapes belonging to various species of Vitis grew wild across North America long before Europeans arrived, forming part of the diet of many Native Americans, but early European colonists judged them unsuitable for wine. In the 19th century, Ephraim Bull of Concord, Massachusetts cultivated seeds from wild Vitis labrusca vines to create the Concord grape, which went on to become a major agricultural crop in the United States. That single act of selective breeding opened the door to an entire domestic grape industry built on native American vines rather than the varieties colonists had originally tried and rejected.

• 3. From Flower To Ripe Berry

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  Grapes grow in clusters ranging from 15 to 300 berries, and within 60 days of fertilization the young fruit first produces tartaric acid, then malic acid as its flesh swells in response to the hormone ethylene, giving the unripe berry its sourness. The ripening stage, called véraison, a term borrowed from French, begins around August and lasts about 45 days under normal Northern Hemisphere conditions, during which the berries darken, grow larger, and start producing sugar. A ripe grape berry is typically ellipsoid, resembling a prolate spheroid, and its flesh is 75 to 85 percent water; before ripening that water comes from the plant's xylem, while afterward the phloem supplies water along with the soluble sugars glucose and fructose. Raw grapes are 81 percent water, 18 percent carbohydrates, and 1 percent protein with negligible fat, and a 100 gram serving supplies 288 kilojoules of food energy along with a moderate amount of vitamin K, at 12 percent of the Daily Value, but little else in significant quantity.

• 4. Why Grapes Change Color

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  Anthocyanins, part of the larger polyphenol family of pigment chemicals, are responsible for the varying shades of purple seen in ripening grape berries and the red wines made from them, with mature fruit ranging through crimson, black, dark blue, yellow, green, orange, and pink. So-called white grapes are actually green and evolved from purple grapes; mutations in two regulatory genes switch off the anthocyanin production that would otherwise turn them purple. That genetic switch, rather than a separate origin, is what separates the entire category of white grapes from their purple ancestors.

• 5. Grapevines Of The World

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  Most domesticated grapes descend from Vitis vinifera, a vine native to the Mediterranean and Central Asia, though smaller amounts of fruit and wine come from other species: Vitis amurensis, the most important Asian species; Vitis mustangensis, the mustang grape found in Mississippi, Alabama, Louisiana, Texas, and Oklahoma; Vitis riparia, a wild vine native to the entire Eastern United States and north into Quebec, sometimes used for winemaking and jam; and Vitis rotundifolia, the muscadine, native from Delaware to the Gulf of Mexico and used for jams and wine. In 2023, the world total of land dedicated to grape growing reached 6595680 hectares, led by Spain at 913000 hectares, France at 753340 hectares, Italy at 713350 hectares, and China at 607030 hectares. About 71 percent of world grape production goes toward wine, 27 percent is eaten as fresh fruit, and 2 percent is dried. World production in 2023 reached 72.5 million tonnes, with China responsible for 19 percent of the total and Italy and France as major secondary producers, while Peru and Chile were that year's leading exporters, each shipping more than half a million tonnes. No reliable statistics break production down by variety, but Sultana, also called Thompson Seedless, is believed to be the most widely planted variety, covering at least 3,600 square kilometres, followed by Airén, with Cabernet Sauvignon, Sauvignon blanc, Cabernet Franc, Merlot, Grenache, Tempranillo, Riesling, and Chardonnay also grown widely.

• 6. Table Grapes Versus Wine Grapes

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  Commercial growers classify grapes as either table or wine grapes according to how they will be consumed, and because grapes stop ripening once picked, their sweetness at harvest depends entirely on timing. Although almost all belong to the single species Vitis vinifera, selective breeding has driven real differences between the two: table cultivars tend to have large, seedless fruit with thin skin, while wine grapes are smaller, usually seeded, and have thicker skins, since much of a wine's aroma comes from the skin. Grapes build sugar on the vine as sucrose produced by photosynthesis is transported into the fruit, then hydrolyzed during ripening into glucose and fructose; wine grapes are typically harvested once their juice reaches about 24 percent sugar by weight, compared to roughly 15 percent for commercial 100 percent grape juice made from table grapes. Seedless cultivars now dominate table grape plantings, and because grapevines propagate vegetatively from cuttings, the absence of seeds poses no barrier to reproduction, only a challenge for breeders, who must use a seeded variety as the female parent or rescue embryos through tissue culture. Essentially all commercial seedless cultivars trace to one of three sources, Thompson Seedless, Russian Seedless, and Black Monukka, and more than a dozen seedless varieties now exist, including Einset Seedless, Reliance, and Venus, bred for hardiness in the cold climates of the northeastern United States and southern Ontario, though the resulting loss of seeds also means a loss of the phytochemicals those seeds would have contained.

• 7. Raisins, Juice, And Vinegar

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  In Europe and North America, dried grapes are called raisins, though in Britain and Ireland three separate varieties are recognized, forcing the EU to use the official term dried vine fruit. A raisin is technically any dried grape, and the English word grape itself derives from the French grappe, meaning bunch, while a currant is specifically a dried Zante Black Corinth grape, its name a corruption of the French raisin de Corinthe, or Corinth grape. A sultana was originally a raisin made from Sultana grapes of Turkish origin, known as Thompson Seedless in the United States, though the term is now applied more broadly. Grape juice is made by crushing and blending grapes and, once pasteurized to remove naturally occurring yeast, will not ferment if kept sterile; in North America the common purple juice comes from Concord grapes and white juice from Niagara grapes, while in California, Sultana grapes are sometimes diverted from the raisin market to make white juice. In the Middle East, a vinegar called husrum, or verjuice, is made by crushing unripened grapes, salting and simmering the juice to remove foam, and storing it under a layer of olive oil; a 12th-century document from the Cairo Geniza mentions unripened husrum grapes shipped from Ashkelon to Egypt, and in Iran a similar sour grape vinegar goes into Shirazi salad.

• 8. The Chemistry In The Skin

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  Winemaking leaves behind pomace, also called marc, made of crushed skins, seeds, stems, and leaves, amounting to some 10 to 30 percent of the total mass of grapes crushed and containing phytochemicals such as unfermented sugars, polyphenols, tannins, and anthocyanins that are sometimes extracted for commercial use. Anthocyanins dominate the polyphenols in purple grape skin, while flavan-3-ols, or catechins, are more abundant in white varieties, and muscadine grapes in particular carry a relatively high phenolic content, including ellagic acid, myricetin, quercetin, kaempferol, and trans-resveratrol. Muscadine seeds hold roughly twice the total polyphenol content of muscadine skins, and grape seed oil, pressed from crushed seeds, is used in cosmeceuticals and skincare for its tocopherols and polyunsaturated fatty acids such as linoleic and oleic acid. Resveratrol, a stilbene compound concentrated mainly in skins and seeds, varies widely by variety, with muscadine grapes carrying about one hundred times more stilbenes than their pulp and fresh grape skin holding roughly 50 to 100 micrograms of resveratrol per gram. None of that chemistry benefits dogs, for whom grapes and raisins pose a genuine health threat, capable of triggering acute kidney failure marked by a lack of urine production, and sometimes proving fatal.