Fruit of the Week - Kiwifruit

The kiwifruit, often shortened to kiwi in many parts of the world, is the edible berry of a cultivar group of the woody vine Actinidia deliciosa and hybrids between this and other species in the genus Actinidia.

The most common cultivars of kiwifruit are oval, about the size of a large hen's egg  2–3 in long and  1¾–2 in diameter. It has a fibrous, dull brown-green skin and bright green or golden flesh with rows of tiny, black, edible seeds. The fruit has a soft texture and a unique flavor, and today is a commercial crop in several countries, mainly in Italy, New Zealand, Brazil and Chile.

Also known as the Chinese gooseberry, the fruit was renamed for export marketing reasons in the 1950s; briefly to melonette, and then later by New Zealand exporters to kiwifruit. The name "kiwifruit" comes from the kiwi — a brown flightless bird and New Zealand's national symbol. Kiwi is also a colloquial name for the New Zealand people.

Kiwifruit is a rich source of vitamin C, 1.5 times the DRI scale in the US. Its potassium content by weight is slightly less than that of a banana. It also contains vitamin E, and a small amount of vitamin A. The skin is a good source of flavonoid antioxidants. The kiwifruit seed oil contains on average 62% alpha-linolenic acid, an omega-3 fatty acid. Usually a medium size kiwifruit contains about 46 calories, 0.3 g fat, 1 g protein, 11 g carbohydrates, and 2.6 g dietary fiber found partly in the edible skin. Kiwifruit is often reported to have mild laxative effects, due to its significant level of dietary fiber.

Kiwifruit can be grown in most temperate climates with adequate summer heat. Whereas 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 production declines as each cane ages. Canes should be pruned off and replaced after their third year.

The plants are normally dioecious, meaning individual plants are either male or female. Only female plants bear fruit, and only when pollenized by a male plant. One male pollenizer is required for each three to eight female vines. An exception is the cultivar 'Issai', a hybrid (Actinidia arguta x polygama) 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.

Kiwifruit is notoriously difficult to pollinate, because the flowers are not very attractive to bees. Some producers blow collected pollen over the female flowers. Generally, the most successful approach, though, 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.

Firm kiwifruit ripen after a few days to a week when stored at room temperature, but should not be kept in direct sunlight. Faster ripening occurs when placed in a paper bag with an apple, pear, or banana. Once a kiwifruit is ripe, however, it is preserved optimally when stored far from other fruits, as it is very sensitive to the ethylene gas they may emit, thereby tending to over-ripen even in the refrigerator. If stored appropriately, ripe kiwifruit normally keep for about one to two weeks.