Kiwifruit

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The Kiwifruit or Chinese Gooseberry is the edible fruit of a Cultivar Group of the woody vine Actinidia deliciosa and hybrids between this and other species in the genus Actinidia.

It is marketed worldwide as kiwifruit but is more commonly called kiwi in North America. The most common cultivars of kiwifruit are oval, and about the size of a large hen's egg (5-8 cm long and 4.5-5.5 cm diameter). It has a hairy, dull green-brown skin that is peeled off before consumption. Inside, the flesh is bright green with rows of small, black, edible seeds. The texture of the fruit is soft and the flavour is sometimes described as a mix of strawberry, banana, and pineapple.

The fruit gets its name from a marketing strategy, naming it after the kiwi, the national bird of New Zealand, where the fruit was first commercially popularised in 1959 by the New Zealand fruit-and-vegetable export company Turners and Growers. Growers gradually adopted the name and in 1974 the kiwifruit became the official trade name.

In North America, the "fruit" part of the name is usually dropped, and most people associate "kiwi" with the fruit rather than the bird. This usage can cause some minor confusion and tends to annoy many New Zealanders. To avoid foreigners becoming confused about what a "kiwi" was, a bird, a fruit or a New Zealander, most New Zealand Kiwifruit is now marketed under the (capitalised) brand name ZESPRI (http://www.zespri.com).

Contents

History

Actinidia deliciosa is native to southern China. Other species of Actinidia are also found in China and range east to Japan and north into southeastern Siberia. Cultivation spread from China in the early 20th century, when seeds were introduced to New Zealand by Isabel Fraser, the principal of Wanganui Girls' College, who had been visiting mission schools in China. The seeds were planted in 1906 by a Wanganui nurseryman, Alexander Allison, with the vines first fruiting in 1910. People who tasted the fruit then thought it had a gooseberry flavour and began to call it the Chinese Gooseberry, but being from the actinidia family it is not related to the Grossulariaceae (gooseberry) family.

The familiar cultivar Actinidia deliciosa 'Hayward' was developed by Hayward Wright in Avondale, New Zealand around 1924. It was initially grown in domestic gardens, but commercial planting began in the 1940s. Italy is now the leading producer of kiwifruit in the world, followed by New Zealand, Chile, France, Greece, Japan and the United States. Kiwifruit is still produced in its birthplace China, but China has never made it to the top 10 list of kiwifruit producing countries. In China, it is grown mainly in the mountainous area upstream of the Yangtze River. It is also grown in other areas of China, including Sichuan.

Names

In Chinese:

Macaque peach (猕猴桃 míhóu táo): the most common name
Unusual fruit or wonder fruit (奇異果 qíyì guǒ): the most common name in Taiwan and Hong Kong (奇异果 kay yee goh). A quasi-transliteration of "kiwifruit".
Yang peach or sun peach (阳桃 yáng táo)
Goat peach (羊桃 yáng táo); these two are homophonous with poplar peach (杨桃), meaning carambola.
Hairy pear (毛梨 máo lí)
Vine pear (藤梨 téng lí)

Cultivars

Almost all kiwifruit in commerce belong to a few cultivars of Actinidia deliciosa: 'Hayward', 'Chico', and 'Saanichton 12'. The fruit of these cultivars are practically indistinguishable from each other and match the description of a standard kiwifruit given at the head of this article.

A new Cultivar Group of Actinidia chinensis known as Golden Kiwifruit, with yellow flesh and sweet flavour resembling a tropical fruit salad, was produced by New Zealand horticulturists and is being marketed worldwide in increasing volumes. Some wild vines in China have yellow fruit but are small and not commercially viable. Seeds from these plants were imported to New Zealand in 1987 and the horticulturists took eleven years to develop the new fruit through cross-pollination and grafting with green kiwi vines. Golden Kiwifruit have a smooth, bronze skin, a pointed cap at one end and distinctive golden yellow flesh. It has a higher market price than green kiwifruit.

Food value

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Sliced kiwifruit

Kiwifruit is a rich source of vitamin C. Its potassium content by weight is slightly less than that of a banana. It also contains vitamins A and E, calcium, iron and folic acid.

Raw kiwifruit is also rich in the protein-dissolving enzyme actinidin (in the same family of thiol proteases as papain), which is commercially useful as a meat tenderizer but can be an allergen for some individuals. Specifically, people allergic to papayas or pineapples are likely to be allergic to kiwifruit also.

This enzyme, which is quickly destroyed by boiling the fruit, makes raw kiwifruit unfit for use in desserts containing milk or any other dairy products. The enzyme will start to dissolve the milk proteins within a few minutes, leaving a very unpleasant bitter taste. But, sliced kiwifruit may be used as a garnish atop whipped cream as on one of New Zealanders favourite desserts, the pavlova, without ill effects.

Cultivation

Kiwifruit can be grown in most temperate climates with adequate summer heat. Where Actinidia deliciosa is not hardy, other species can be grown as substitutes.

Kiwifruit is commercially grown on sturdy support structures, as it can produce several tonnes per hectare, more than the rather weak vines can support. These are generally equipped with a watering system for irrigation and frost protection in the spring.

Kiwifruit vines require vigorous pruning, similar to that of grapevines. Fruit is borne on one-year-old and older canes, but declines as each cane ages. Canes should be pruned off and replaced after their third year.

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Male Kiwi-flower

Kiwifruit plants are normally dioecious, meaning that individual plants are male or female. Only female plants bear fruit, and only when pollenized by a male plant. One male pollenizer is required be planted for each three to eight female vines. An exception is the cultivar 'Issai', a hybrid (Actinidia arguta x rufa) from Japan, which produces perfect flowers and can self-pollinate; unfortunately it lacks vigour, is less hardy than most A. arguta forms and is not a large producer.

Mature kiwifruit

Kiwifruit is notoriously difficult to pollinate because the flowers are not very attractive to bees. Some producers blow collected pollen over the female flowers. But generally the most successful approach is saturation pollination, where the bee populations are made so large (by placing hives in the orchards) that bees are forced to use this flower because of intense competition for all flowers within flight distance.

External links

Purdue University NewCROP (http://www.hort.purdue.edu/newcrop/morton/kiwifruit_ars.html)
NCBI's taxonomy browser (http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Undef&name=kiwifruit&srchmode=1&keep=1&a=Go&lvl=3) (as of August 1 2002)
Photos of kiwifruit and alfalfa pollination in California (http://www.ellendick.com/wildbees/)
Nutritional informatin for 1 large Kiwifruit (http://www.elook.org/nutrition/fruits/2272-2.html) also per 100 grams (http://www.elook.org/nutrition/fruits/2272.html)
How to prepare a Kiwi (http://vaseline.dot.co.il/pages_eng/kiwi.htm)ca:Kiwi (fruita)