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History of Cultivation
C. sativa is found across the Mediterranean region, from the Caspian Sea to the Atlantic Ocean. It is thought to have survived the last ice age in several refuges in southern Europe, on the southern coast of the Black sea with a main centre on the southern slope of the Caucasus and in the region of north-western Syria, possibly extending into Lebanon. Pollen data indicates that the first spreading of C. sativa due to human activity started around 2100-2050 B.C. in Anatolia, northeastern Greece and southeastern Bulgaria. Compared to other crops, the sweet chestnut was probably of relatively minor importance and distributed very heterogeneously throughout these regions. The first charcoal remains of chestnut found only date from around 850-950 B.C., making it very difficult to infer a precise origin history. A newer but more reliable source are the literary works of Ancient Greece, with the richest being Theophrastus’ Inquiry into plants written in the third century B.C. Theophrastus focuses mainly on the use of chestnut wood as timber and charcoal, only mentioning the use of the fruit once when commenting on the digestive difficulties it causes, but praising its nourishing quality. Several Greek authors wrote about medicinal properties of the chestnut, specifically as a remedy against lacerations of the lips and of the oesophagus.

Similar to the introduction of grape vine and olive cultivation to the Latin world, the chestnut is thought to have been introduced during the colonisation of the Italian peninsula by the Greeks. Further clues pointing to this theory can be found in the work of Pliny the Elder, who mentions only Greek colonies in connection with chestnut cultivation. Today’s phylogenetic map of the chestnut, while not fully understood, shows greater genetic similarity between Italian and western Anatolian chestnut trees compared to eastern Anatolian specimen, reinforcing these findings. Nonetheless, until the end of the pre-Christian era, the spread and use of the chestnut in Italy remained limited. Carbonised chestnuts were found in the Roman Villa Torre Annunziata, destroyed by the eruption of Mount Vesuvius in A.D. 79.

Clues in art and literature indicate a dislike of the sweet chestnut by the Roman aristocracy. Like Theophrastus, Latin authors are sceptical of the sweet chestnut as a fruit, and Pliny the Elder even goes as far as admiring how well nature has hidden this fruit of apparently so little value. In the beginning of the Christian era, people probably started to realize the value and versatility of chestnut wood, leading to a slow spread of the cultivation of C. sativa trees, a theory that is supported by pollen data and literary sources, as well as the increased use of chestnut wood as poles and in supporting structures, wood works and pier building between A.D. 100 and 600.

Increasing chestnut pollen appearances in Switzerland, France, Germany and the Iberian peninsula in the first century A.D. suggests the spreading of cultivated chestnut trees by the Romans. Contrary to that notion, other scientists found no indication of the Romans spreading C. Sativa before the fifth century. In fact, so far no center of chestnut cultivation outside the Italian peninsula in Roman times has been detected. Widespread use of chestnut in western Europe started in the early Middle Ages and flourished in the late Middle Ages. Since the beginning of the 20th century, due to depopulation of the countryside and the abandonment of the chestnut as a staple food as well as the spread of chestnut blight and ink disease, C. sativa cultivation has dramatically decreased. Nowadays, sweet chestnut production is sometimes seen to be at a turning point again, because the development of high-value chestnut products combined with changing needs of an urban society is leading to a revival in C. sativa cultivation.

Distribution
The species is widely distributed throughout Europe, where in 2004 C. sativa was grown on 2.25 million hectares of forest, of which 1.78 million hectares were mainly cultivated for wood and 0.43 million hectares for fruit production. Italy, France, southern Switzerland, Spain, Portugal and Greece are countries with a strong sweet chestnut tradition, with trees cultivated intensively in coppices and orchards. Countries like England, Croatia, Turkey and Georgia only have a partially developed chestnut tradition due to geography or history. In some countries, C. sativa has only been introduced recently, for example in Slovakia or the Netherlands.

General
[already existing]

Characteristics
Castanea sativa reaches a height of 20 to 25 meters, although certain specimen grow up to 30 to 35 meters with a circumference of one to two, in rare cases up to 12 meters. The trunk is mostly straight with branching starting at low heights. Sweet chestnut trees attain an age of 500 to 600 years. If cultivated, sweet chestnut trees might live up to 1000 years. Their large genetic diversity and different cultivars are being nursed for uses like flour, boiling, roasting, drying, candying or wood. The brown greyish bark has a net shaped venation and deep fissures. Oblong-lanceolate leaves are 8-25 cm long and 5-9 cm broad, and have a dentate-crenate margin with a bright green upper leaf surface.

Reproduction
The monoecious sweet chestnut develops in late June to July and is pollinated by wind or insects. The sweet chestnut is self incompatible, meaning that the plant can’t pollinate itself, making cross-pollination is necessary. Male and female flowers can be distinguished: male flowers are gathered in catkins of 5 to 15 cm length, while female flowers are positioned at the base of the male flowers in the upper part of the current year's shoots. It is the female flowers that then develop first into spiny cupules or blurs, producing three to seven brownish nuts that are shed during September to October. However, some cultivars only produce one large nut per cupule, and in rare cases up to three nuts. The nut itself is composed of two skins: an external, shiny brown part, and an internal skin adhering to the fruit. Inside, there is an edible, creamy-white part developed from the cotyledon.

Pests and Diseases
The two major fungal pathogens for the sweet chestnut are the chestnut blight (Cryphonectria parasitica) and the ink disease caused by phytophthora cambivora and phytophthora cinnamomi. In North America as well as in Southern Europe cryphonectria parasitica destroyed most of the chestnut population in the 20th century. With biological control the population of the sweet chestnut is not threatened anymore by the disease and is regenerating. Ink disease is infesting trees mostly in humid soils, with the mycelium invading the root and resulting in wilting of the leaf. Absence of fruit formation leads to die back of the petal. The disease is named after the black exudates resulting at the base of the trunk. Nowadays there are cultivars that are resistant to the ink disease. Phytophthora cambivora caused serious damage in Asia and the USA and it still continues to destroy new plantations in Europe.

Another serious pest which is difficult to control is the gall wasp (Dryocosmus kuriphylus) which was recently introduced in Southern Europe, originating from Asia.

Cultivation Forms
Three different cultivation systems for the sweet chestnut can be distinguished:


 * Coppicing: Mainly for wood extraction. Standard conditions yield 15 m3 wood per ha and year.


 * Selve: Fruit production from grafted trees. The trees have a short tribe and a big crown. Trees have a high density and the space between the trees is often used as pasture.


 * High forest: wood and fruit production. This one is less intensive with a yield of 4-12 dt/ha and replacement of trees every 50-80 years. The trees grow from seeds and they build a dense canopy.

Soil Requirements
The sweet chestnut tree grows well on limestone-free and deeply weathered soil. The optimal pH value is between 4.5 and 6 and it cannot tolerate soil compaction. The tolerance to wet ground and to clay-rich soils is very low.

Climate Requirements
It is a heat-loving tree which needs a long vegetation period. The optimal average temperature is between 8°C and 15° C and in January the temperature must be not below -1°C even if it has a good tolerance until -15°C. Low temperature in autumn can damage the fruit. The maximal altitude is strongly dependent on the climate. In general, the climate should be similar to viticulture. The optimal precipitations are between 400 and 1600 mm.

Seedbed Requirements and Sowing
Seeds must be stratified at 2-3°C and the germination happens 30-40 days later. After a year, the young trees are being transplanted.

Field Management
The field management is dependent on the cultivation system. While cleaning the soil from the leaves and pruning is the norm, the use of fertilizer, irrigation and pesticides is less common and reserved for more intensive cultivation.

Proliferation
Proliferation is possible in two different ways: generative and vegetative. Both are practiced in the cultivation. The vegetative proliferation is done through coppice and stolon. The sweet chestnut is self-sterile.

Harvest
The fruit yield per tree is normally between 30-100 kg, but can get as high as 300 kg. Harvest time is between middle of September and middle of November. There are three harvesting techniques:


 * By hand: The chestnuts are harvested with the help of rakes or brooms. With a performance of 5 until 30 kg every hour depending on the soil relief. Also, the capsule makes the harvest more complicated and potentially painful for the worker.


 * By hand with nets: This technique is less time-consuming and protects the fruits from injuries. However, the soil must be prepared before harvest.


 * Mechanical: The fruits are collected with a machine that works similarly to a vacuum cleaner. Doing so is time-saving and economical, but it’s possible that some fruits get injured, and a big initial investment is needed. Furthermore, a visual sorting is not possible.

The total world chestnut harvest was 1,17 Mio Tons in 2006, but only 151 000 Tons were C. sativa.

Post-harvest Treatment
The most widespread treatment before storage is water curing, where the sweet chestnuts stay in water for nine days. The aim of this practice is to limit the main storage problems that are present for the sweet chestnut: the presence of insect worms and fungi development. As an alternative to water curing, hot water treatments are commercially in use.

After the water bath the sweet chestnuts are stored in a controlled environment with high carbon dioxide concentrations. In contrast to a cold storage system, where the fruit are stored at low temperatures but with normal air, the controlled environment method avoids flesh hardening, which impacts the processability of the product.

Cuisine
[already existing]

Food Constituents
Castanea sativa is considered as having very interesting nutritional characteristics. The fruit contains significant amounts of a wide range of valuable nutrients. In the past, its characteristic and nutritional components gave sweet chestnut an important role in human nutrition due to its beneficial health effects. Sweet Chestnut is also appreciated in a gluten-free diet. Furthermore, this characteristic is valuable in cases of celiac diseases as well as reducing coronary heart diseases and cancer rates. Various composition and health studies have shown its big potential as a food ingredient and functional food. The fat content is very low and is dominated for the most part by unsaturated fatty acids. Sweet chestnut is a good source for starch, although it is generally true that chestnuts of all varieties contain about the same amount of starch. The energy value per 100 g (3.5 oz) of C. sativa amounts to 891 kJ (213 kcal). C. sativa is characterized by high moisture content which ranges from 41 % to 59 % and a considerable level of starch (~40 g 100 g-1 dry matter). Regarding mineral content, the chestnut provides a good source for Cu, Fe, Mg, Mn and K. Its sugar content ranges from 14 % to 20 % dry weight depending on the cultivar; which is very important, since the sensory appeal of sweet chestnut is correlated with its sugar content. However, high sugar amounts seem to have a negative impact on the fiber content. Generally, glucose content in European chestnuts is very low and ranges from zero to traces. Instead, fructose is mostly responsible for the sweet taste.

Processing
Sweet chestnut is suited for human nutrition. Most sweet chestnut is consumed in processed form, which has an impact on the nutrient composition. Its naturally high concentration of organic acids is a key factor of influencing the organoleptic characteristics of fruits and vegetables, namely flavor. Organic acids are thought to play an important role against diseases as an antioxidant. Heat appears to be the most influencing factor when it comes to decreasing the organic acid content. However, even after heating sweet chestnuts, antioxidant activity remains relatively high. On the other hand, the consumer must consider that roasting, boiling or frying has a big impact on the nutritional profile of chestnut. Vitamin C significantly decreases between 25-54 % when boiled and 2-77 % when roasted. Nevertheless, roasted or boiled chestnuts may still be a solid vitamin C source, since 100 gram still represent about 20 % of the recommended daily dietary intake. The sugar content is also affected by the high temperatures. Four processes are decisive for the degrading process of sugar while cooking: hydrolysis of starch to oligosaccharide and monosaccharide, decomposition of sucrose to glucose and fructose, caramelization of sugars and degradation of sugars. Organic acids are also affected by high temperatures: their content decreases about 50 % after frying, and 15 % after boiling. Responsible for the aromatic characteristics of cooked chestnuts is the effect of degradation of saccharides, proteins and lipids, the caramelization of saccharides and the maillard reaction that is reducing sugar and amino acids.