Monday, November 29, 2010

Healthy Fruit: Peach

The peach tree (Prunus persica) is a species of Prunus native to China that bears an edible juicy fruit called a peach. It is a deciduous tree growing to 4–10 m (13–33 ft) tall, belonging to the subfamily Prunoideae of the family Rosaceae. It is classified with the almond in the subgenus Amygdalus within the genus Prunus, distinguished from the other subgenera by the corrugated seed shell.
The leaves are lanceolate, 7–16 cm (2.8–6.3 in) long, 2–3 cm (0.79–1.2 in) broad, pinnately veined. The flowers are produced in early spring before the leaves; they are solitary or paired, 2.5–3 cm diameter, pink, with five petals. The fruit has yellow or whitish flesh, a delicate aroma, and a skin that is either velvety (peaches) or smooth (nectarines) in different cultivars. The flesh is very delicate and easily bruised in some cultivars, but is fairly firm in some commercial varieties, especially when green. The single, large seed is red-brown, oval shaped, approximately 1.3–2 cm long, and is surrounded by a wood-like husk. Peaches, along with cherries, plums and apricots, are stone fruits (drupes).
The scientific name persica, along with the word "peach" itself and its cognates in many European languages, derives from an early European belief that peaches were native to Persia (now Iran). The modern botanical consensus is that they originate in China, and were introduced to Persia and the Mediterranean region along the Silk Road before Christian times. Cultivated peaches are divided into clingstones and freestones, depending on whether the flesh sticks to the stone or not; both can have either white or yellow flesh. Peaches with white flesh typically are very sweet with little acidity, while yellow-fleshed peaches typically have an acidic tang coupled with sweetness, though this also varies greatly. Both colours often have some red on their skin. Low-acid white-fleshed peaches are the most popular kinds in China, Japan, and neighbouring Asian countries, while Europeans and North Americans have historically favoured the acidic, yellow-fleshed kinds.
Although its botanical name Prunus persica suggests the peach is native to Persia, peaches actually originated in China where they have been cultivated since the early days of Chinese culture. Peaches were mentioned in Chinese writings as far back as the 10th century BC and were a favoured fruit of kings and emperors. Recently, the history of cultivation of peaches in China has been extensively reviewed citing numerous original manuscripts dating back to 1100 B.C.
Its English name derives originally from the Latin Prunus persica, then persica, then pessica, then pesca, then the French peche, then peach in Middle English.
The peach was brought to India and Western Asia in ancient times. Alexander the Great introduced the fruit into Europe after he conquered the Persians. Then it was brought to America by Spanish explorers in the 16th century and eventually made it to England and France in the 17th century, where it was a prized, albeit rare, treat.
California today grows 65% of peaches grown for commercial production in the United States, but the states of Colorado, Michigan, and Washington also grow a significant amount. Italy, China, India and Greece are major producers of peaches outside of the United States.
Peach plants grow very well in a fairly limited range, since they have a chilling requirement that tropical areas cannot satisfy, and they are not very cold-hardy. The trees themselves can usually tolerate temperatures to around -26 to -30 °C (-15 to -22 °F), although the following season's flower buds are usually killed at these temperatures, leading to no crop that summer. Flower bud kill begins to occur between -15 and -25 °C (5 and -13 °F) depending on the cultivar (some are more cold-tolerant than others) and the timing of the cold, with the buds becoming less cold tolerant in late winter. Certain cultivars are more tender and others can tolerate a few degrees colder. In addition, a lot of summer heat is required to mature the crop, with mean temperatures of the hottest month between 20 and 30 °C (68 and 86 °F). Another problematic issue in many peach-growing areas is spring frost. The trees tend to flower fairly early in spring. The blooms often can be damaged or killed by freezes; typically, if temperatures drop below about −4 °C (24.8 °F), most flowers will be killed. However, if the flowers are not fully open, they can tolerate a couple of degrees colder.
Most peach trees sold by nurseries are named cultivars budded or grafted onto a suitable rootstock. It is also possible to grow a tree from either a peach or nectarine seed, but the fruit quality of the resulting tree will be very unpredictable. Peaches should be located in full sun, and with good air flow. This allows cold air to flow away on frosty nights and keeps the area cool in summer. Peaches are best planted in early winter, as this allows time for the roots to establish and to sustain the new spring growth. When planting in rows, plant north–south.
For optimum growth, peach trees require a constant supply of water. This should be increased shortly before the harvest. The best tasting fruit is produced when the peach is watered throughout the season. Drip irrigation is ideal, with at least one dripper per tree. Although it is better to use multiple drippers around the tree, this is not necessary. A quarter of the root being watered is sufficient.
Peaches should be stored at room temperature and refrigeration should be avoided as this can lessen the taste of the peach. Peaches do not ripen after being picked from the tree, so storing for ripening is not necessary.
Peaches are known in China, Japan, Korea, Laos, and Vietnam not only as a popular fruit but for the many folk tales and traditions associated with it.
Nutrition and health
A medium peach 75 g (2.6 oz), has 30 Calories, 7 g of carbohydrates (6 g sugars and 1 g fibre), 1 g of protein, 140 mg of potassium, and 8% of the daily value (DV) for vitamin C.
As with many other members of the rose family, peach seeds contain cyanogenic glycosides, including amygdalin (note the subgenus designation: Amygdalus). These substances are capable of decomposing into a sugar molecule and hydrogen cyanide gas. While peach seeds are not the most toxic within the rose family, that dubious honour going to the bitter almond, large doses of these chemicals from any source are hazardous to human health.
Peach allergy or intolerance is a relatively common form of hypersensitivity to proteins contained in peaches and related fruit (almonds). Symptoms range from local symptoms (e.g. oral allergy syndrome, contact urticaria) to systemic symptoms including anaphylaxis (e.g. urticaria, angioedema, gastrointestinal and respiratory symptoms). Adverse reactions are related to the "freshness" of the fruit: peeled or canned fruit may be tolerated.

Peaches (edible part) : Nutritional value per 100 g (3.5 oz)
Energy 165 kJ (39 kcal)

Carbohydrates 9.5 g
Sugars 8.4 g | Dietary fiber 1.5 g
Fat 0.3 g | Protein 0.9 g
Vitamin A equiv. 16 μg (2%)
Folate (Vit. B9) 4 μg (1%) | Vitamin C 6.6 mg (11%)
Iron 0.25 mg (2%) | Potassium 190 mg (4%)
Percentages are relative to US recommendations for adults. 
Source: USDA Nutrient database

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