The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family (also known as the nightshades). The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species. Potatoes were first introduced outside the Andes region four centuries ago, and have become an integral part of much of the world’s cuisine. It is the world’s fourth-largest food crop, following rice, wheat, and maize. Long-term storage of potatoes requires specialised care in cold warehouses.
Wild potato species occur throughout the Americas, from the United States to Uruguay. The potato was originally believed to have been domesticated independently in multiple locations, but later genetic testing of the wide variety of cultivars and wild species proved a single origin for potatoes in the area of present-day southern Peru (from a species in the Solanum brevicaule complex), where they were domesticated 7,000–10,000 years ago.Following centuries of selective breeding, there are now over a thousand different types of potatoes.Of these subspecies, a variety that at one point grew in the Chiloé Archipelago (the potato’s south-central Chilean sub-center of origin) left its germplasm on over 99% of the cultivated potatoes worldwide.
Following the Spanish conquest of the Inca Empire, the Spanish introduced the potato to Europe in the second half of the 16th century. The staple was subsequently conveyed by European mariners to territories and ports throughout the world. The potato was slow to be adopted by distrustful European farmers, but soon enough it became an important food staple and field crop that played a major role in the European 19th century population boom. However, lack of genetic diversity, due to the very limited number of varieties initially introduced, left the crop vulnerable to disease. In 1845, a plant disease known as late blight, caused by the fungus-like oomycete Phytophthora infestans, spread rapidly through the poorer communities of western Ireland, resulting in the crop failures that led to the Great Irish Famine. Nonetheless, thousands of varieties persist in the Andes, where over 100 cultivars might be found in a single valley, and a dozen or more might be maintained by a single agricultural household.
The annual diet of an average global citizen in the first decade of the 21st century included about 33 kg (73 lb) of potato. However, the local importance of potato is extremely variable and rapidly changing. It remains an essential crop in Europe (especially eastern and central Europe), where per capita production is still the highest in the world, but the most rapid expansion over the past few decades has occurred in southern and eastern Asia. China is now the world’s largest potato-producing country, and nearly a third of the world’s potatoes are harvested in China and India.
Uses
In central African regions of relatively high production, potatoes are beaten with grains and legumes into a stiff porridge, or boiled or roasted and eaten whole.
Nutrition
The potato contains vitamins and minerals, as well as an assortment of phytochemicals, such as carotenoids and natural phenols. Chlorogenic acid constitutes up to 90% of the potato tuber natural phenols. Others found in potatoes are 4-O-caffeoylquinic (crypto-chlorogenic acid), 5-O-caffeoylquinic (neo-chlorogenic acid), 3,4-dicaffeoylquinic and 3,5-dicaffeoylquinic acids. A medium-size 150 g (5.3 oz) potato with the skin provides 27 mg of 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. The fiber content of a potato with skin (2 g) is equivalent to that of many whole grain breads, pastas, and cereals.
In terms of nutrition, the potato is best known for its carbohydrate content (approximately 26 grams in a medium potato). The predominant form of this carbohydrate is starch. A small but significant portion of this starch is resistant to digestion by enzymes in the stomach and small intestine, and so reaches the large intestine essentially intact. This resistant starch is considered to have similar physiological effects and health benefits as fiber: It provides bulk, offers protection against colon cancer, improves glucose tolerance and insulin sensitivity, lowers plasma cholesterol and triglyceride concentrations, increases satiety, and possibly even reduces fat storage.The amount of resistant starch in potatoes depends much on 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.
The nutrients of the potato seem to be fairly evenly distributed between the flesh and the skin. For a medium potato, with and without the skin, nutritiondata.com gives the following:
| Nutrient | Without skin (156 g) (% RDA) | With skin (173 g) (% RDA) |
|---|---|---|
| Vitamin C | 33 | 28 |
| Thiamin | 11 | 7 |
| Niacin | 11 | 12 |
| Vitamin B6 | 23 | 27 |
| Folate | 4 | 12 |
| Pantothenic Acid | 9 | 7 |
| Iron | 3 | 10 |
| Magnesium | 10 | 12 |
| Potassium | 17 | 26 |
| Copper | 17 | 10 |
| Dietary Fiber | 9 | 15 |
The cooking method used can significantly impact the nutrient availability of the potato.
Potatoes are often broadly classified as high on the glycemic index (GI) and so are often excluded from the diets of individuals trying to follow a low-GI diet. In fact, the GI of potatoes can vary considerably depending on type (such as red, russet, white, or Prince Edward), origin (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 with what it is consumed (i.e., the addition of various high-fat or high-protein toppings).
Potatoes are not considered by the NHS as counting towards the five portions of fruit and vegetables diet.
Toxicity
Potatoes contain toxic compounds known as glycoalkaloids, of which the most prevalent are solanine and chaconine. Solanine is also found in other plants in the family Solanaceae, which includes such plants as the deadly nightshade (Atropa belladonna), henbane (Hyoscyamus niger) and tobacco (Nicotiana) as well as the potato, eggplant, and tomato. This toxin affects the nervous system, causing weakness and confusion.
These compounds, which protect the plant from its predators, are, in general, concentrated in its leaves, stems, sprouts, and fruits. Exposure to light, physical damage, and age increase glycoalkaloid content within the tuber; the highest concentrations occur just underneath the skin. 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 may cause headaches, diarrhea, cramps, and in severe cases coma and death; however, poisoning from potatoes occurs very rarely. Light exposure causes greening from chlorophyll synthesis, 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.
The toxic fruits produced by mature potato plants
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). While a normal potato has 12-20 mg/kg of glycoalkaloid content, a green tuber contains 250-280 mg/kg, and green skin 1500-2200 mg/kg. In normal potatoes, analysis has shown solanine levels may be as little as 3.5% of the breeders’ maximum, with 7–187 mg/kg being found.
The U.S. National Toxicology Program suggests that the average American consume at most 12.5 mg/day of solanine from potatoes (the toxic dose is actually several times this, depending on body weight). Douglas L. Holt, the State Extension Specialist for Food Safety at the University of Missouri, 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.
Health
Due to carbohydrate and fat content, potatoes are considered to make a person obese if used in excess i.e. more than RDA of carbohydrates and fats. Research by the University of California, Davis and the National Center for Food Safety and Technology, Illinois Institute of Technology demonstrates that people can include potatoes in their diet and still lose weight.
Uses
Potatoes are used to brew alcoholic beverages such as vodka, potcheen, or akvavit.
They are also used as food for domestic animals.
Potato starch is used in the food industry as, for example, thickeners and binders of soups and sauces, in the textile industry, as adhesives, and for the manufacturing of papers and boards.
Maine companies are exploring the possibilities of using waste potatoes to obtain polylactic acid for use in plastic products; other research projects seek ways to use the starch as a base for biodegradable packaging.
Culinary uses
Potatoes are prepared in many ways: skin-on or peeled, whole or cut up, with seasonings or without. The only requirement involves cooking to swell the starch granules. 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 or yogurt 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 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.
Potatoes are boiled between 10 and 25 minutes, depending on size and type, to become soft.