Potato
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| Potato | ||||||||||||||||
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| Binomial name | ||||||||||||||||
| Solanum tuberosum L. |
The potato (Solanum tuberosum) is a perennial plant of the Solanaceae, or nightshade, family, commonly grown for its starchy tuber. Potatoes are the world's most widely grown tuber crop, and the fourth largest food crop in terms of fresh produce — after rice, wheat, and maize ('corn'). The potato was domesticated in southern Peru[1] and northern Bolivia and is important to the culture of the Andes, where farmers grow many different varieties that have a remarkable diversity of colors and shapes, with over 100 varieties sometimes being grown in a single valley.[2] In pre-Colombian times they were also widely cultivated on Chiloé Island, in Chile. Potatoes spread from South America to Spain and from there to the rest of the world after European colonization in the late 1400s and early 1500s. They soon became an important field crop.
- For instance, the potato was a staple food for sailors in Spanish ships. After the wreck of the Spanish Armada in 1588, English coastal villagers rescued potatoes and planted them.
- In 1845, a fungal disease, Phytophthora infestans, also known as late blight, spread rapidly through the poorer communities of western Ireland, resulting in the Great Irish Famine. Unfortunately the local population had begun to rely on the potato as a staple food and when crops failed, year after year, huge numbers of people died. Others emigrated, largely to the United States, blaming the British government for the situation.
- The potato is also strongly associated with Idaho, Maine, Prince Edward Island, Ireland, Jersey and Russia because of its large role in the agricultural economy and/or history of these regions.
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[edit] Botanical description
Potato plants grow high to the ground and bear yellow to silver flowers with yellow stamens.
Potatoes are cross-pollinated mostly by bumble bees that carry pollen from other potato plants, but a substantial amount of self-fertilizing occurs as well. Any potato variety can also be propagated vegetatively by planting tubers, pieces of tubers, cut to include at least one or two eyes, or also by cuttings, a practice used in greenhouses for the production of healthy seed tubers.
Some commercial potato varieties do not produce seeds at all (they bear imperfect flowers) and are propagated only from tuber pieces. Confusingly, these tubers or tuber pieces are called "seed potatoes".
After potato plants flower, some varieties will produce small green fruits that look similar to green cherry tomatoes. These produce seeds like other fruits. Each of the fruits can contain up to 300 true seeds. One can separate seeds from the fruits by putting them in a blender on a slow speed with some water, then leaving them in water for a day so that the seeds will sink and the rest of the fruit will float. All new potato varieties are grown from seeds, also called "true seed" or "botanical seed" to distinguish it from seed tubers. However, some horticulturists sell chimeras made by grafting a tomato plant onto a potato plant, which can produce both edible tomatoes and potatoes although that practice is not very widespread.
[edit] Etymology
The English word potato comes from Spanish patata, ultimately from Nahuatl potatl, potentially its first name.
Bulgarian картоф, as well as Russian картофель and German Kartoffel, derive from the Italian word tartufoli, which was given to potato because of its similarity to truffles (Italian: tartufo).
Another common name is "ground apple": pomme de terre in French, aardappel in Dutch, תפוח אדמה in Hebrew (often written just as פוד), and Erdapfel in Austrian German. In 16th century French, pomme meant "fruit", thus pomme de terre meant "ground fruit" and was probably literally loan translated to other languages when potatoes were introduced. In Polish potato is called just ziemniaki, and in Slovak zemiak, from the word for "ground".
Different names for the potato developed in China's various regions, the most widely used names in standard Chinese today are "horse-bell yam" (马铃薯 - mǎlíngshǔ), "earth bean" (土豆 - tǔdòu), and "foreign taro" (洋芋 - yángyù).
[edit] Origin and history
There is general agreement between contemporary botanists that the potato originated in the Andes, all the way from Colombia to northern Argentina, but with a concentration of genetic diversity, both in the form of cultivated and wild species, in the area of modern day Peru. The potatoes cultivated in the Andes are not all the same species. The major species is Solanum tuberosum ssp. andigena (a tetraploid with 48 chromosomes,) then there are four diploid species (with 24 chromosomes) by the names of Solanum stenotomum, Solanum phureja, Solanum goniocalyx and Solanum ajanhuiri. There are two triploid species (with 36 chromosomes) Solanum chaucha and Solanum juzepczukii, and finally, there is one pentaploid cultivated species (with 60 chromosomes) called Solanum curtilobum.
Andean potatoes are adapted to short day conditions and Chilean potatoes to long day conditions. There is sufficient evidence that the tetraploid Andean short day potato was the one that first arrived in Southern Spain in about 1565, from where it spread to the rest of Europe, adapting to European long day conditions in a period of about two hundred years. In order to botanically distinguish potatoes adapted to short days from those thriving and producing tubers under long day conditions, Solanum tuberosum has been split into two subspecies by present-day taxonomists, Solanum tuberosum ssp. tuberosum (adapted to long days) and Solanum tuberosum ssp. andigena (adapted to short days.) Apart from their different photoperiodic reaction, these two subspecies are also distinct morphologically, though the differences are apparent only to an experienced taxonomist. Russian taxonomists did, in fact, create two different species in the early part of the 20th century, Solanum tuberosum and Solanum andigenum, to mark the same distinction. The process of adaptation to long days has happened once before as the potato moved from the Andes to the south of the continent. This was before the Europeans arrived in South America. Chile still has a large amount of valuable potato germplasm adapted to long days.
Historical and genetic evidence suggests that the potato reached India not very much later than Europe, probably taken there by the Portuguese. In isolated areas in the Himalayas of India and Nepal, so called "desi" potatoes are still grown, and they are very similar to the short day adapted modern Andean potato, Solanum tuberosum ssp. andigena.
There are about five thousand potato varieties world wide. Three thousand of them are found in the Andes alone, mainly in Peru, Bolivia, Ecuador and Colombia. They belong to eight or nine species, depending on the taxonomic school. Apart from the five thousand cultivated varieties, there are about 200 wild species, many of which can be cross-bred with cultivated species, which has been done repeatedly to transfer resistances to certain pests and diseases from the gene pool of wild species to the gene pool of cultivated potato species. The list of varieties found in European, North American or Asian markets is very limited, and these varieties are all of the same species, Solanum tuberosum ssp. tuberosum.
These potatoes are often referred to as "Irish" potatoes in the English speaking world because of their association with the Great Irish Famine, which began in 1845 and lasted for six years. The Irish peasant population had become highly dependent on the potato because of the relatively large amount of food that could be produced on fairly small holdings. Immigrant farmers from the Palatinate region of Germany brought their own crops, such as turnips, to Western Ireland. They were much less dependent on the potato than their native Irish neighbors and were largely spared the effects of the potato famine. The disease killing the Irish potato crop was the late blight fungus Phytophtora infestans. The long lasting after effects of this famine are well known and well documented.
What is less well known is the role of the British during the potato famine. Rich aristocratic British landowners continued to export grain from Ireland to other parts of the world even as tens of thousands of Irish men, women and children were starving to death. Fortunately, this was not the practice of all of them, there were some British owned estates where not one Irish peasant starved during the famine. Authors like Salaman have written in detail about that situation, which has also been recognized by contemporary British historians.
Most modern potatoes grown in North America arrived through European settlement and not independently from the South American sources. Still, one wild potato species, Solanum fendleri, is found as far north as Texas and used in breeding for resistance to a nematode species attacking cultivated potatoes. A secondary center of genetic variability of the potato is Mexico, where important wild species are found that have been used extensively in modern breeding, such as the hexaploid Solanum demissum, as a source of resistance to the devastating late blight disease.
The potato became an important staple crop in northern Europe as the climate changed due to the Little Ice Age, when traditional crops in this region did not produce as reliably as before. At times when and where most other crops would fail, potatoes could still typically be relied upon to contribute adequately to food supplies during the colder years. The potato was not popular in France during this time, and it is believed that some of the infamous famines could have been lessened if French farmers had adopted the potato. Today, the potato forms an important part of the traditional cuisine of the British Isles, northern Europe, central Europe and eastern Europe. As of 2007, Germany has a higher consumption of potato per capita than any other country on earth.
[edit] Food value
| Potato, raw, with peel Nutritional value per 100 g (3.5 oz) | ||||||||||||||||||||||||||||||||
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| Energy 80 kcal 320 kJ | ||||||||||||||||||||||||||||||||
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| Percentages are relative to US recommendations for adults. | ||||||||||||||||||||||||||||||||
Nutritionally, potatoes are best known for their carbohydrate content (approximately 26 grams in a medium potato). Starch is the predominant form of carbohydrate found in potatoes. A small but significant portion of the starch in potatoes is resistant to enzymatic digestion in the stomach and small intestine and, thus, reaches the large intestine essentially intact. This resistant starch is considered to have similar physiological effects and health benefits of fiber (e.g., provide bulk, offer protection against colon cancer, improve glucose tolerance and insulin sensitivity, lower plasma cholesterol and triglyceride concentrations, increase satiety, and possibly even reduce fat storage) (Cummings et al. 1996; Hylla et al 1998; Raban et al. 1994). The amount of resistant starch found in potatoes is highly dependent upon preparation methods. Cooking and then cooling potatoes significantly increases resistant starch. For example, cooked potato starch contains about 7% resistant starch, which increases to about 13% upon cooling (Englyst et al. 1992).
Potatoes contain a number of important vitamins and minerals. A medium potato (150g/5.3 oz) with the skin provides 27 mg vitamin C (45% of the Daily Value (DV)), 620 mg of potassium (18% of DV), 0.2 mg vitamin B6 (10% of DV) and trace amounts of thiamin, riboflavin, folate, niacin, magnesium, phosphorus, iron, and zinc. Moreover, the fiber content of a potato with skin (2 grams) equals that of many whole grain breads, pastas, and cereals. In addition to vitamins, minerals and fiber, potatoes also contain an assortment of phytochemicals, such as carotenoids and polyphenols. The notion that “all of the potato’s nutrients” are found in the skin is an urban legend. While the skin does contain approximately half of the total dietary fiber, the majority (more than 50%) of the nutrients are found within the potato itself. The cooking method used can significantly impact the nutrient availability of the potato.
New and fingerling potatoes offer the advantage that they contain fewer toxic chemicals. Such potatoes offer an excellent source of nutrition. Peeled, long-stored potatoes have less nutritional value, although they still have potassium and vitamin B.
Potatoes are often broadly classified as “high” on the glycemic index (GI) and thus are frequently excluded from the diets of individuals trying to follow a “low GI” eating regimen. In fact, the GI of potatoes can vary considerably depending on the type (i.e., red vs. russet vs. white vs. Prince Edward), origin (i.e., where it was grown), preparation methods (i.e., cooking method, whether it is eaten hot or cold, whether it is mashed or cubed or consumed whole, etc), and what it is consumed with (i.e., the addition of various high fat or high protein toppings) (Fernandes et al. 2006).
[edit] General methods
Potatoes are prepared in many ways: skin-on or peeled, whole or cut up, with seasonings or without. The only requirement involves cooking to break down the starch. Most potato dishes are served hot, but some are first cooked then served cold, notably potato salad and potato chips/crisps.
Common dishes are: mashed potatoes, which are first boiled (usually peeled), and then mashed with milk and butter; whole baked potatoes; boiled or steamed potatoes; French-fried potatoes or chips; cut into cubes and roasted; scalloped, diced, or sliced and fried (home fries); grated into small thin strips and fried (hash browns); grated and formed into dumplings, Rösti or potato pancakes. Unlike many foods, potatoes can also be easily cooked in a microwave oven and still retain nearly all of their nutritional value, provided that they are covered in ventilated plastic wrap to prevent moisture from escaping—this method produces a meal very similar to a steamed potato while retaining the appearance of a conventionally baked potato. Potato chunks also commonly appear as a stew ingredient.
[edit] Regional dishes
Peruvian Cuisine naturally contains the potato as a primary ingredient in many dishes, as around 3,000 varieties of this tuber are grown there.[3] Some of the more famous dishes include Papa a la huancaina, Papa rellena, Ocopa, Carapulcra, Causa and Cau Cau among many others.
Mashed potatoes form a major component of several traditional dishes from the British Isles such as shepherd's pie, bubble and squeak, champ and the 'mashit tatties' (Scots language) which accompany haggis. They are also often sautéed to accompany a meal.
Colcannon is a traditional Irish dish involving mashed potato combined with shredded cabbage and onion.
Potatoes are very popular in continental Europe as well. In Italy, they serve to make a type of pasta called gnocchi. Potatoes form one of the main ingredients in many soups such as the pseudo-French vichyssoise and Albanian potato and cabbage soup. In western Norway, komle is popular.
In the United States, potatoes have become one of the most widely consumed crops, and thus have a variety of preparation methods and condiments. One popular favorite involves a baked potato with cheddar cheese (or sour cream and chives) on top, and in New England "smashed potatoes" (a chunkier variation on mashed potatoes, retaining the peel) have great popularity. Potato flakes are popular as an instant variety of mashed potatoes, which reconstitute into mashed potatoes by adding water, plus butter & salt for taste. A regional dish of Central New York, salt potatoes are bite-sized new potatoes boiled in water saturated with salt then served with melted butter.
In Northern Europe, especially Denmark, Sweden and Finland, newly harvested, early ripening varieties are considered a special delicacy. Boiled whole and served with dill, these "new potatoes" are traditionally consumed together with Baltic herring.
A traditional Canary Islands dish is Canarian wrinkly potatoes or Papas arrugadas.
A traditional Acadian dish from New Brunswick is known as poutine râpée. The Acadian poutine is a ball of grated and mashed potato, salted, sometimes filled with pork in the center, and boiled. The result is a moist ball about the size of a baseball. It is commonly eaten with salt and pepper or brown sugar. It is believed to have originated from the German Klöße, prepared by early German settlers who lived among the Acadians.
Poutine, by contrast, is a hearty serving of french fries, fresh cheese curds and hot gravy. Tracing its origins to Quebec in the 1950s, it has become popular across Canada and can usually be found where Canadians gather abroad.
[edit] Toxic compounds in potatoes
Early Rose variety
Potatoes contain glycoalkaloids, toxic compounds, of which the most prevalent are solanine and chaconine. Cooking at high temperatures (over 170 °C or 340 °F) partly destroys these. The concentration of glycoalkaloid in wild potatoes suffices to produce toxic effects in humans. Glycoalkaloids occur in the greatest concentrations just underneath the skin of the tuber, and they increase with age and exposure to light. Glycoalkaloids may cause headaches, diarrhea, cramps and in severe cases coma and death; however, poisoning from potatoes occurs very rarely. Light exposure also causes greening, thus giving a visual clue as to areas of the tuber that may have become more toxic; however, this does not provide a definitive guide, as greening and glycoalkaloid accumulation can occur independently of each other. Some varieties of potato contain greater glycoalkaloid concentrations than others; breeders developing new varieties test for this, and sometimes have to discard an otherwise promising cultivar.
Breeders try to keep solanine levels below 200 mg/kg (200 ppmw). However, when these commercial varieties turn green, even they can approach concentrations of solanine of 1000 mg/kg (1000 ppmw). In normal potatoes though, analysis has shown solanine levels may be as little as 3.5% of the breeders' maximum, with 7–187 mg/kg being found.[4] The National Toxicology Program suggests that the average American consumes at most 12.5 mg/person/day of solanine from potatoes (note that the toxic dose is actually several times this, depending on body weight). Dr. Douglas L. Holt, the State Extension Specialist for Food Safety at the University of Missouri - Columbia, notes that no reported cases of potato-source solanine poisoning have occurred in the U.S. in the last 50 years and most cases involved eating green potatoes or drinking potato-leaf tea.
Solanine is also found in other plants, mainly in the mostly-deadly nightshade family, which includes a minority of edible plants including the potato and the tomato, and other typically more dangerous plants like tobacco. This poison affects the nervous system causing weakness and confusion.