The chestnut (Castanea) group is a genus of eight or nine species of deciduous trees and shrubs in the beech family Fagaceae, native to temperate regions of the Northern Hemisphere.
The name also refers to the edible nuts they produce.
Chestnuts belong to the family Fagaceae, which also includes oaks and beeches. The four main species are commonly known as European, Chinese, Japanese, and American chestnuts, some species called chinkapin or chinquapin:
European species sweet chestnut (Castanea sativa) (also called "Spanish chestnut" in the US) is the only European species of chestnut, though it was successfully introduced to the Himalayas and other temperate parts of Asia. Unrelated but externally similar species of horse chestnut are abundant around Europe.
Asiatic species Castanea crenata (Japanese chestnut, Korean chestnut), Castanea mollissima (Chinese chestnut), Castanea davidii (China), Castanea henryi (Chinese chinkapin, also called Henry’s chestnut – China) and Castanea seguinii (also called Seguin’s chestnut – China)
American species These include Castanea dentata (American chestnut – Eastern states), Castanea pumila (American- or Allegheny chinkapin, also known as "dwarf chestnut" – Eastern states), Castanea alnifolia (Southern states), Castanea ashei (Southern states), Castanea floridana (Southern states) and Castanea paucispina (Southern states).
Chestnuts should not be confused with horse chestnuts (genus Aesculus), which are not related to Castanea and are named for producing nuts of similar appearance, but which are mildly poisonous to humans, nor should they be confused with water chestnut (family Cyperaceae), which are also unrelated to Castanea and are tubers of similar taste from an aquatic herbaceous plant. Other trees commonly mistaken for chestnut trees are the chestnut oak (Quercus prinus) and the American beech (Fagus grandifolia), both of which are also in Fagaceae.
The name "chestnut" is derived from an earlier English term "chesten nut", which descends from the Old French word chastain (Modern French, châtaigne).
The name Castanea is probably derived from the old name for the sweet chestnut, either in Latin or in Ancient Greek. Another possible source of the name is the town of Kastania in Thessaly, Greece; more probable, though, is that the town took its name from the most common tree growing around it. In the Mediterranean climate zone, chestnut trees are rarer in Greece because the chalky soil is not conducive to the tree’s growth. Kastania is located on one of the relatively few sedimentary or siliceous outcrops. They grow so abundantly there, their presence would have determined the place’s name. Still others take the name as coming from the Greek name of Sardis glans (Sardis acorn) – Sardis being the capital of Lydia, Asia Minor, from where the fruit had spread.
The name is cited twice in the King James Version of the Bible. In one instance, Jacob puts peeled twigs in the water troughs to promote healthy offspring of his livestock. Although it may indicate another tree, it indicates the fruit was a local staple food in the early 17th century.
These synonyms are or have been in use: Fagus Castanea (used by Linnaeus in first edition of Species Plantarum, 1753), Sardian nut, Jupiter’s nut, husked nut, and Spanish chestnut (U.S.).
Chestnut trees are of moderate growth rate (for the Chinese chestnut tree) to fast-growing for American and European species. Their mature heights vary from the smallest species of chinkapins, often shrubby, to the giant of past American forests, C. dentata that could reach 60 m. Between these extremes are found the Japanese chestnut (C. crenata) at 10 m average; followed by the Chinese chestnut (C. mollissima) at about 15 m, then the European chestnut (C. sativa) around 30 m.
The Chinese and more so the Japanese chestnuts are both often multileadered and wide-spreading, whereas European and especially American species tend to grow very erect when planted among others, with little tapering of their columnar trunks, which are firmly set and massive. When standing on their own, they spread on the sides and develop broad, rounded, dense crowns at maturity. The two latter’s foliage has striking yellow autumn colouring.
Its bark is smooth when young, of a vinous maroon or red-brown colour for the American chestnut, grey for the European chestnut. With age, American species’ bark becomes grey and darker, thick and deeply furrowed; the furrows run longitudinally, and tend to twist around the trunk as the tree ages; it sometimes reminds one of a large cable with twisted strands.
The leaves are simple, ovate or lanceolate, 10–30 cm long and 4–10 cm wide, with sharply pointed, widely spaced teeth, with shallow rounded sinuates between.
The flowers follow the leaves, appearing in late spring or early summer or into July. They are arranged in long catkins of two kinds, with both kinds being borne on every tree. Some catkins are made of only male flowers, which mature first. Each flower has eight stamens, or 10 to 12 for C. mollissima. The ripe pollen carries a heavy, sweet odour that some people find too sweet or unpleasant. Other catkins have these pollen-bearing flowers, but also carry near the twig from which these spring, small clusters of female or fruit-producing flowers. Two or three flowers together form a four-lobed prickly calybium, which ultimately grows completely together to make the brown hull, or husk, covering the fruits.
Chestnut flowers are not self-compatible, so two trees are required for pollination. All Castanea species readily hybridize with each other.
The fruit is contained in a spiny (very sharp) cupule 5–11 cm in diameter, also called "bur" or "burr". The burrs are often paired or clustered on the branch and contain one to seven nuts according to the different species, varieties, and cultivars. Around the time the fruits reach maturity, the burrs turn yellow-brown and split open in two or four sections. They can remain on the tree longer than they hold the fruit, but more often achieve complete opening and release the fruits only after having fallen on the ground; opening is partly due to soil humidity.
The chestnut fruit has a pointed end with a small tuft at its tip (called "flame" in Italian), and at the other end, a hilum – a pale brown attachment scar. In many varieties, the fruit is flattened on one or two sides. It has two skins. The first one is a hard, shiny, brown outer hull or husk, called the pericarpus; the industry calls this the "peel". Underneath the pericarpus is another, thinner skin, called the pellicle or episperm. The pellicle closely adheres to the seed itself, following the grooves usually present at the surface of the fruit. These grooves are of variable sizes and depths according to the species and variety.
The fruit inside these shows two cotyledons with a creamy-white flesh throughout, except in some varieties which show only one cotyledon, and whose episperm is only slightly or not intruded at all. Usually, these varieties have only one large fruit per burr, well rounded (no flat face) and which is called "marron" (marron de Lyon in France, marron di Mugello in Italy, or paragon).
Chestnut fruit have no epigeal dormancy and germinate right upon falling to the ground in the autumn, with the roots emerging from the seed right away and the leaves and stem the following spring. Because the seeds lack a coating or internal food supply, they lose viability soon after ripening and must be planted immediately.
The superior fruiting varieties among European chestnuts have good size, sweet taste, and easy-to-remove inner skins. American chestnuts are usually very small (around 5 g), but sweet-tasting with easy-to-remove pellicles. Some Japanese varieties have very large nuts (around 40 g), with typically difficult-to-remove pellicles. Chinese chestnut pellicles are usually easy to remove, and their sizes vary greatly according to the varieties, although usually smaller than the Japanese chestnut.
The sweet chestnut was introduced into Europe from Sardis, in Asia Minor; the fruit was then called the Sardian nut. It has been a staple food in southern Europe, Turkey, and southwestern and eastern Asia for millennia, largely replacing cereals where these would not grow well, if at all, in mountainous Mediterranean areas. Evidence of its cultivation by man is found since around 2000 BC. Alexander the Great and the Romans planted chestnut trees across Europe while on their various campaigns. A Greek army is said to have survived their retreat from Asia Minor in 401–399 BC thanks to their stores of chestnuts. Ancient Greeks, such as Dioscorides and Galen, wrote of chestnuts to comment on their medicinal properties – and of the flatulence induced by eating too much of it. To the early Christians, chestnuts symbolized chastity. Until the introduction of the potato, whole forest-dwelling communities which had scarce access to wheat flour relied on chestnuts as their main source of carbohydrates. In some parts of Italy, a cake made of chestnuts is used as a substitute for potatoes. In 1583, Charles Estienne and Jean Liébault wrote, "an infinity of people live on nothing else but (the chestnut)". In 1802, an Italian agronomist said of Tuscany that "the fruit of the chestnut tree is practically the sole subsistence of our highlanders", while in 1879 it was said that it almost exclusively fed whole populations for half the year, as "a temporary but complete substitution for cereals".
Boundary records compiled in the reign of John already showed the famous Tortworth Chestnut in South Gloucestershire, as a landmark; and it was also known by the same name of "Great Chestnut of Tortworth" in the days of Stephen. This tree measured over 15 m in circumference at 1.5 m from the ground in 1720. The chestnut forests on Mount Etna contain many trees that are said to be even larger. Chestnut trees particularly flourish in the Mediterranean basin. In 1584, the governor of Genua, which dominated Corsica, ordered all the farmers and landowners to plant four trees yearly, among which a chestnut tree – plus olive, fig and mulberry trees (this assumedly lasted until the end of Genoese rule over Corsica in 1729). Many communities owe their origin and former richness to the ensuing chestnut woods. In France, the marron glacé, a candied chestnut involving 16 different processes in a typically French cooking style, is always served at Christmas and New Year’s time. In Modena, Italy, they are soaked in wine before roasting and serving, and are also traditionally eaten on Saint Simon’s Day in Tuscany. It is traditional to eat roasted chestnuts in Portugal on St. Martin’s Day.
Their popularity declined during the last few centuries, partly due to their reputation of "food for poor people". Many people did not want to take chestnut bread as "bread" because chestnut flour does not rise. Some slandered chestnut products in such words as the bread which "gives a sallow complexion" written in 1770, or in 1841 "this kind of mortar which is called a soup". The last decades’ worldwide renewal may have profited from the huge reforestation efforts started in the 1930s in the United States to establish varieties of C. sativa which may be resistant to chestnut blight, as well as to relieve the strain on cereal supplies.
The main region in Italy for chestnut production is the Mugello region; in 1996, the European Community granted the fruit Protected Geographic Indication (equivalent to the French Appellation d’Origine Contrôlée) status to the Mugello sweet chestnut. It is markedly sweet, peels easily, is not excessively floury or astringent, and has notes of vanilla, hazelnut, and, more subtly, fresh bread. There is no unpleasant aroma, such as yeast, fungus, mold or paper, which sometimes occur with other chestnuts. The main regions in France for chestnut production are the départements of Ardèche, with the famous "Châtaigne d’Ardèche" (A.O.C), of the Var (Eastern Provence), of the Cévennes (Gard and Lozère départements) and of the Lyon region. France annually produces over 1,000 metric tons, but still imports about 8,000 metric tons, mainly from Italy.
In Portugal’s archipelago of Madeira, chestnut liquor is a traditional beverage, and it is gaining popularity with the tourists and in continental Portugal.
Always served as part of the New Year menu in Japan, chestnuts represent both success and hard times – mastery and strength. The Japanese chestnut (kuri) was in cultivation before rice and the Chinese chestnut (C. mollissima) possibly for 2,000 to 6,000 years.
During British colonial rule in the mid-1700s to 1947, the sweet chestnut (C. sativa) was widely introduced in the temperate parts of the Indian Subcontinent, mainly in the lower-to-middle Himalayas. They are widely found in British-founded hill stations in northern India, and to a lesser extent in Bhutan and Nepal. They are mainly used as an ornamental tree and are found in almost all British-founded botanical gardens and official governmental compounds (such as larger official residences) in temperate parts of the Indian Subcontinent.
China has about 300 chestnut cultivars. Moreover, the Dandong chestnut (belonging to the Japanese chestnut C. crenata) is a major cultivar in Liaoning Province.
American Indians were eating the American chestnut species, mainly C. dentata and some others, long before European immigrants introduced their stock to America, and before the arrival of chestnut blight. In some places, such as the Appalachian Mountains, one-quarter of hardwoods were chestnuts. Mature trees often grew straight and branch-free for 15 m, up to 100 feet, averaging up to 5 ft in diameter. For three centuries, most barns and homes east of the Mississippi River were made from it. In 1911, the food book The Grocer’s Encyclopedia noted that a cannery in Holland included in its "vegetables-and-meat" ready-cooked combinations, a "chestnuts and sausages" casserole besides the more classic "beef and onions" and "green peas and veal". This celebrated the chestnut culture that would bring whole villages out in the woods for three weeks each autumn (and keep them busy all winter), and deplored the lack of food diversity in the United States’s shop shelves.
Soon after that, though, the American chestnuts were nearly wiped out by chestnut blight. The discovery of the blight fungus on some Asian chestnut trees planted on Long Island, New York, was made public in 1904. Within 40 years, the nearly four billion-strong American chestnut population in North America was devastated; only a few clumps of trees remained in Michigan, Wisconsin, California and the Pacific Northwest. Due to disease, American chestnut wood almost disappeared from the market for decades, although quantities can still be obtained as reclaimed lumber. Today, they only survive as single trees separated from any others (very rare), and as living stumps, or "stools", with only a few growing enough shoots to produce seeds shortly before dying. This is just enough to preserve the genetic material used to engineer an American chestnut tree with the minimal necessary genetic input from any of the disease-immune Asiatic species. Efforts started in the 1930s are still ongoing to repopulate the country with these trees, in Massachusetts and many places elsewhere in the United States. In the 1970s, geneticist Charles Burnham began back-breeding Asian chestnut into American chestnut populations to confer blight resistance with the minimum difference in genes. In the 1950s, the Dunstan chestnut was developed in Greensboro, N.C., and constitutes the majority of blight-free chestnuts produced in the United States annually.
Today, the nut’s demand outstrips supply. The United States imported 4,056 metric tons of European in-shell chestnuts worth $10 million in 2007. The U.S. chestnut industry is in its infancy, producing less than 1% of total world production. Since the mid-20th century, most of the US imports are from Southern Italy, with the large, meaty, and richly flavored Sicilian chestnuts being considered among the best quality for bulk sale and supermarket retail. Some imports come from Portugal and France. The next two largest sources of imports are China and South Korea. The French varieties of marrons are highly favoured and sold at high prices in gourmet shops.
A study of the sector in 2005 found that US producers are mainly part-timers diversifying an existing agricultural business, or hobbyists. Another recent study indicates that investment in a new plantation takes 13 years to break even, at least within the current Australian market. Starting a small-scale operation requires a relatively low initial investment; this is a factor in the small size of the present production operations, with half of them being within 40,000 m2. Another predetermining factor in the small productivity of the sector is that most orchards have been created less than 10 years ago, so have young trees which are as now barely entering commercial production. Assuming a 10 kilograms yield for a 10-year-old tree is a reliable conservative estimate, though some exceptional specimens of that age have yielded 100 kilograms. So, most producers earn less than $5,000 per year, with a third of the total not having sold anything so far.
Moreover, the plantings have so far been mostly of Chinese species, but the products are not readily available. The American Chestnut Foundation recommends waiting a little while more before large-scale planting. This is because it and its associates (the American Chestnut Cooperators’ Foundation and many others from education, research and industry sectors contributing to the program) are at the last stages of developing a variety that is as close as possible to the American chestnut, while having incorporated the blight-resistant gene of the Asiatic species. Considering the additional advantage that chestnut trees can be easily grown organically, and assuming the development of brands in the market, it has been asserted that, everything else being equal, home-grown products would reach higher prices than imports, the high volume of which indicates a market with expanding prospects. As of 2008, the price for chestnuts sold fresh in the shell ranges from $3.30/kg wholesale to about $11/kg retail, depending mainly on the size.
AUSTRALIA – NEW ZEALAND
The Australian gold rush of the 1850s and 1860s led to the first recorded plantings of European chestnut trees, brought in from Europe by the first settlers. Along the years, most chestnut tree plantations were C. sativa stock, which is still the dominant species. Some of these are still standing today. Some trees in northern Victoria are around 120 years old and up to 60 m tall.
Chestnuts grow well in southwest Western Australia, which has cold winters and warm to hot summers. As of 2008, the country has just under 350 growers, annually producing around 1,200 metric tons of chestnuts, of which 80% come from northeast Victoria. The produce is mostly sold to the domestic fresh fruit market. Chestnuts are now slowly gaining popularity in Australia. A considerable increase in production is expected in the next 10 years, due to the increase in commercial plantings during the last 15 to 25 years. By far, the most common species in Australia is the European chestnut, but small numbers of the other species, as well as some hybrids have been planted.
The Japanese chestnut (C. crenata) does well in wet and humid weather and in hot summers (about 30 °C); and was introduced to New Zealand in the early 1900s, more so in the upper North Island region.
Chestnuts depart from the norm for culinary nuts in that they have very little protein or fat, their calories coming chiefly from carbohydrates. Fresh chestnut fruits have about 180 calories (800 kJ) per 100 grams of edible parts, which is much lower than walnuts, almonds, other nuts and dried fruit (about 600 kcal/100 g). Chestnuts contain very little fat, mostly unsaturated, and no gluten.
Their carbohydrate content compares with that of wheat and rice; chestnuts have twice as much starch as the potato on an as-is basis. In addition, chestnuts contain about 8% of various sugars, mainly sucrose, glucose, fructose, and, in a lesser amount, stachyose and raffinose, which are fermented in the lower gut, producing gas. In some areas, sweet chestnut trees are called "the bread tree". When chestnuts are just starting to ripen, the fruit is mostly starch and is very firm under finger pressure from the high water content. As the chestnuts ripen, the starch is slowly converted into sugars, and moisture content also starts decreasing. Upon pressing the chestnut, a slight ‘give’ can be felt; the hull is not so tense, and space occurs between it and the flesh of the fruit. They are the only "nuts" that contain vitamin C, with about 40 mg per 100 g of raw product, which is about 65% of the U.S. recommended daily intake. The amount of vitamin C decreases by about 40% after heating. Fresh chestnuts contain about 52% water by weight, which evaporates relatively quickly during storage; they can lose as much as 1% of weight in one day at 20 °C and 70% relative humidity.
Tannin is contained in the bark as well as in the wood, leaves, and seed husks. The husks contain 10–13% tannin.
The fruit can be peeled and eaten raw, but it can be somewhat astringent, especially if the pellicle is not removed.
Another method of eating the fruit involves roasting, which does not require peeling. Roasting requires scoring the fruit beforehand to prevent explosion of the fruit due to expansion. Once cooked, its texture is slightly similar to that of a baked potato, with a delicate, sweet, and nutty flavour. This method of preparation is popular in many countries, where the scored chestnuts may be cooked mixed with a little sugar.
Chestnuts can be dried and milled into flour, which can then be used to prepare breads, cakes, pies, pancakes, pastas, polenta (known in Corsica as pulenda), or used as thickener for stews, soups, and sauces. Chestnut cake may be prepared using chestnut flour. In Corsica, the flour is fried into doughnut-like fritters called fritelli and made into necci, pattoni, castagnacci, and cialdi. The flour can be light beige like that from Castagniccia, or darker in other regions. It is a good solution for long storage of a nutritious food. Chestnut bread can stay fresh as long as two weeks.
The nuts can also be eaten candied, boiled, steamed, deep-fried, grilled, or roasted in sweet or savoury recipes. They can be used to stuff vegetables, poultry, fowl, and other edibles. They are available fresh, dried, ground, or canned (whole or in puree).
Candied chestnuts (whole chestnuts candied in sugar syrup, then iced) are sold under the French name marrons glacés or Turkish name kestane şekeri ("sugared chestnuts"). They appeared in France in the 16th century. Towards the end of 19th century, Lyon went into a recession with the collapse of the textile market, notably silk. Clément Faugier, a civil engineer, was looking for a way to revitalize the regional economy. In 1882 at Privas, he invented the technology to make marrons glacés on an industrial scale (although a great number of the more than 20 necessary steps from harvest to the finished product are still accomplished manually). Chestnuts are picked in autumn, and candied from the start of the following summer for the ensuing Christmas. Thus, the marrons glacés eaten at Christmas are those picked the year before.
In Hungarian cuisine, cooked chestnuts are puréed, mixed with sugar (and usually rum), forced through a ricer, and topped with whipped cream to make a dessert called gesztenyepüré (chestnut purée). In Swiss cuisine, a similar dish made with kirsch and butter is called vermicelles. A French version is known as "Mont Blanc".
A fine granular sugar can be obtained from the fermentation of the juice, as well as a beer; the roasted fruit provides a coffee substitute. Parmentier, who among other things was a famous potato promoter, extracted sugar from chestnuts and sent a chestnut sugarloaf weighing several pounds to the Academy of Lyon. The continental blockade following shortly after (1806–1814) increased the research into developing chestnuts as a source of sugar, but Napoleon chose beets instead.
Sweet chestnuts are not easy to peel when cold. One kilogram of untainted chestnuts yields about 700 g of shelled chestnuts.
Chestnut is of the same family as oak, and likewise its wood contains many tannins. This renders the wood very durable, gives it excellent natural outdoor resistance, and saves the need for other protection treatment. It also corrodes iron slowly, although copper, brass, or stainless metals are not affected.
Chestnut timber is decorative. Light brown in color, it is sometimes confused with oak wood. The two woods’ textures are similar. When in a growing stage, with very little sap wood, a chestnut tree contains more timber of a durable quality than an oak of the same dimensions. Young chestnut wood has proved more durable than oak for woodwork that has to be partly in the ground, such as stakes and fences.
After most growth is achieved, older chestnut timber tends to split and warp when harvested. The timber becomes neither as hard nor as strong as oak. The American chestnut C. dentata served as an important source of lumber, because that species has long, unbranched trunks. In Britain, chestnut was formerly used indiscriminately with oak for the construction of houses, millwork, and household furniture. It grows so freely in Britain that it was long considered a truly native species, partly because the roof of Westminster Hall and the Parliament House of Edinburgh were mistakenly thought to be constructed of chestnut wood. Chestnut wood, though, loses much of its durability when the tree is more than 50 years old, and despite the local chestnut’s quick growth rate, the timber used for these two buildings is considerably larger than a 50-year-old chestnut’s girth. It has been proven that the roofs of these buildings are actually Durmast oak, which closely resembles chestnut in grain and color.
It is therefore uncommon to find large pieces of chestnut in building structures, but it has always been highly valued for small outdoor furniture pieces, fencing, cladding (shingles) for covering buildings, and pit-props, for which durability is an important factor. In Italy, chestnut is also used to make barrels used for aging balsamic vinegar and some alcoholic beverages, such as whisky or lambic beer. Of note, the famous 18th-century "berles" in the French Cévennes are cupboards cut directly from the hollowed trunk.
Fabric can be starched with chestnut meal. Linen cloth can be whitened with chestnut meal. The leaves and the skins (husk and pellicle) of the fruits provide a hair shampoo.
Hydrolysable chestnut tannins can be used for partial phenol substitution in phenolic resin adhesives production and also for direct use as resin.
Chestnut extracts were evaluated through several biochemical assays showing evident antioxidant properties.
Chestnut buds have been listed as one of the 38 substances used to prepare Bach flower remedies, a kind of alternative medicine promoted for its effect on health. However, according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".
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