Thursday, 18 August 2016


“So the pie isn’t perfect? Cut it into wedges. Stay in control, and never panic.” - Martha Stewart

Rhubarb (Rheum rhabarbarum) is a species of plant in the family Polygonaceae. It is a herbaceous perennial growing from short, thick rhizomes. It produces large poisonous leaves that are somewhat triangular, with long fleshy edible stalks and small flowers grouped in large compound leafy greenish-white to rose-red inflorescences.

In culinary use, fresh raw leaf stalks (petioles) are crisp (similar to celery) with a strong, tart taste. Although rhubarb is not a true fruit, in the kitchen it is usually prepared as if it were. Most commonly, the stalks are cooked with sugar and used in pies, crumbles and other desserts. A number of varieties have been domesticated for human consumption, most of which are recognised as Rheum x hybridum by the Royal Horticultural Society. Rhubarb contains anthraquinones including rhein, and emodin and their glycosides (e.g. glucorhein), which impart cathartic and laxative properties. It is hence useful as a cathartic in case of constipation.

Rhubarb is grown widely, and with greenhouse production it is available throughout much of the year. Rhubarb grown in hothouses (heated greenhouses) is called “hothouse rhubarb”, and is typically made available at consumer markets in early spring, before outdoor cultivated rhubarb is available. Hothouse rhubarb is usually brighter red, more tender and sweeter-tasting than outdoors rhubarb. In temperate climates, rhubarb is one of the first food plants harvested, usually in mid- to late spring (April/May in the Northern Hemisphere, October/November in the Southern Hemisphere), and the season for field-grown plants lasts until September.

In the northwestern US states of Oregon and Washington, there are typically two harvests, from late April to May and from late June into July. Rhubarb is ready to consume as soon as harvested, and freshly cut stalks are firm and glossy. In the United Kingdom, the first rhubarb of the year is harvested by candlelight in forcing sheds where all other light is excluded – a practice that produces a sweeter, more tender stalk. These sheds are dotted around the noted “Rhubarb Triangle” of Wakefield, Leeds, and Morley.

Rhubarb damaged by severe cold should not be eaten, as it may be high in oxalic acid, which migrates from the leaves and can cause illness. The colour of rhubarb stalks can vary from the commonly associated crimson red, through speckled light pink, to simply light green. The colour results from the presence of anthocyanins, and varies according to both rhubarb variety and production technique. The colour is not related to its suitability for cooking: The green-stalked rhubarb is more robust and has a higher yield, but the red-coloured stalks are much more popular with consumers.

Rhubarb is grown primarily for its fleshy stalks, technically known as petioles. The use of rhubarb stems as food is a relatively recent innovation. This usage was first recorded in 17th-century England after affordable sugar became available to common people, and reached a peak between the 20th century's two world wars. Commonly, it is stewed with sugar or used in pies and desserts, but it can also be put into savoury dishes or pickled. Rhubarb can be dehydrated and infused with fruit juice. In most cases, it is infused with strawberry juice to mimic the popular strawberry rhubarb pie. Rhubarb root produces a rich brown dye similar to walnut husks. It is used in northern regions where walnut trees do not survive.

For cooking, the stalks are often cut into small pieces and stewed (boiled in water) with added sugar, until soft. Little water is added, as rhubarb stalks already contain a great deal of water. Rhubarb should be processed and stored in glass or stainless steel containers which are unaffected by residual acid content. Spices such as cinnamon, nutmeg, and ginger are sometimes added. Stewed rhubarb or rhubarb sauce, like applesauce, is usually eaten cold. Pectin, or sugar with pectin, can be added to the mixture to make jams. A similar preparation, thickened with cornstarch or flour, is used as filling for rhubarb pie, tarts, and crumbles, leading to the nickname “pie plant”, by which it is referred to in many 19th-century cookbooks, as well as by American author Laura Ingalls Wilder in her short novel “The First Four Years”. The term "pie plant" is still used regionally in the U.S.

In recent times rhubarb has often been paired with strawberries to make strawberry-rhubarb pie. In former days, a common and affordable sweet for children in parts of the United Kingdom and Sweden was a tender stick of rhubarb, dipped in sugar. It is still eaten this way in western Finland, Norway, Iceland and sometimes Sweden, and some other parts of the world. In Chile, Chilean rhubarb, which is only very distantly related, is sold on the street with salt or dried chili pepper, not sugar. Rhubarb can be used to make a fruit wine or “sima”. Being a little sour, it is very refreshing and can be drunk cold, especially during the summer. It is also used to make compote.

In traditional Chinese medicine, rhubarb roots have been used as a laxative for several millennia. Rhubarb also appears in medieval Arabic and European prescriptions. It was one of the first Chinese medicines to be imported to the West from China. A pigment found in rhubarb called parietin, has been identified from an FDA database of 2,000 known suppressors of 6PGD, to have killed half the human leukaemia cells over two days in the laboratory. The pigment also slowed the growth of other human cancer cells in mouse models. A more-potent derivative of the parietin called S3 may even cut the growth of lung cancer cells implanted in mice by two-thirds, over the course of 11 days.

Rhubarb leaves contain poisonous substances, including oxalic acid, which is a nephrotoxic and corrosive acid that is present in many plants. Humans have been poisoned after ingesting the leaves, a particular problem during World War I when the leaves were mistakenly recommended as a food source in Britain. The toxic rhubarb leaves have been used in flavouring extracts, after the oxalic acid is removed by treatment with precipitated chalk.

In the language of flowers, a leafy rhubarb stalk signifies “you are two-faced”, while a flower spike means “I’ll take your advice”.

No comments:

Post a Comment