Sweet Chestnut (Castanea sativa)
Sweet Chestnut, the remedy for those suffering from anguish and deep despair, is made by the boiling method.
Native to Southern Europe, the sweet chestnut was introduced to Britain by the Romans. They ground the nuts to make a flour or coarse meal and this was used to make porridge. Nuts are surrounded by a spiny husk or cupule which gives them protection from predators and cupules usually contain two to four nuts. John Evelyn, the English gardener and diarist, wrote that the nuts were ‘delicacies for princes and a lusty and masculine food for rusticks, and able to make women well-complexioned’. However, although commonly eaten in other parts of Europe, in England they were usually fed to pigs.
The best chestnuts come from marrons – varieties which are monospermic (ie only produce one seed per fruit) and a meal made from these contains 15 % sugar. This was sometimes used to whiten linen cloth. Candied chestnuts are known as marron glacés and they are also eaten raw or roasted. Roasted chestnuts are traditionally used as a stuffing for turkey.
Cooking foods changes their chemical composition and the nutritional value, colour and flavour also change. When chestnuts are roasted, the volatile compounds γ-butyrolactone (GBL) and furfural are formed. The former has a sweet caramel flavour and the latter a woody, almond flavour. But the compounds produced are not always beneficial – acrylamide, a probable human carcinogen and known neurotoxin, is also produced. The median acrylamide content found in tests of commercial samples was 90 μg/kg and in 2009 tolerable limits for carcinogenic effects of 2.6 μg/kg body weight/day and for neurotoxicity of 40μ μg/kg body weight/day, were estimated. For a 70 kg person, in the absence of any other sources, this would suggest eating 2 kg a day would be safe!
γ-Butyrolactone occurs in small quantities in some wines but for commercial use it is synthesised. As well as its use as a flavouring, it is used as a solvent and reagent in chemistry. It can be used as a solvent for cured superglue. Although it is not medicinally active, it is a prodrug for γ-hydroxybutyric acid or GHB. This means it is metabolised in the body to produce GHB, which produces intoxication similar to that of alcohol.
GHB is used recreationally, to increase athletic performance and as a date rape drug. Medicinally, it is sometimes used to treat narcolepsy and was previously used in anaesthesia. In the UK, GBL and GHB are class 3 drugs, so possession or sale for human consumption is illegal. GBL is permitted for use as a food flavouring or other legitimate uses, but this must be registered.
Furfural is produced commercially from agricultural by-products like oat hulls and is used as a chemical feedstock and solvent. Although used as a flavouring agent in low concentrations, it is toxic and a skin irritant.
The Romans valued chestnut flower honey for its taste and it is used for dressing wounds, skin ulcers and burns today due to its antibacterial and antioxidant properties. Leaves were chewed or made into a tea to treat fevers. The major medicinal use, however, was to treat paroxysmal and convulsive coughs such as whooping-cough and other conditions of the respiratory system.
The wood is more durable than oak although it loses durability after around 50 years old, so is used when the wood has to be sunk into the ground. In south east England sweet chestnut is coppiced to produce poles. The wood and bark are a rich source of tannins which are used in the tanning of leather.
A 250-year-old sweet chestnut tree was the focus of an anti-road protest in London in 1993. The tree, on George Green in Wanstead, was to be cut down to make way for an extension to the M11 motorway. Protestors slept in the tree for 5 weeks before they were evicted and the removal of the tree was also challenged in court. One argument was that, as letters were delivered to the tree by the Royal Mail, it constituted a legal dwelling. The tree was eventually cut down in December 1993.