Adzuki bean

Vigna angularis, also known as theadzuki bean(Japanese:小豆,Hepburn:azuki),azuki bean,aduki bean,red bean, orred mung bean, is anannualvinewidely cultivated throughoutEast Asiafor its small (approximately5 mm or1⁄4in long)bean. Thecultivarsmost familiar in East Asia have a uniform red color, but there are white,black, gray, and variouslymottledvarieties.
Scientists presumeVigna angularisvar.nipponensisis theprogenitor.
The wild ancestor of cultivated adzuki bean is probablyVigna angularisvar.nipponensis,which is distributed across East Asia.SpeciationbetweenVigna angularisvar.nipponensisandVigna angularisvar.angularisoccurred around 50,000 years ago.Archaeologists estimate it was domesticated around 3000 BC.However, adzuki beans, as well as soybeans, dating from 3000 BC to 2000 BC are indicated to still be largely within the wild size range. Enlarged seeds occurred during the laterBronze AgeorIron Age, periods with plough use.
Domesticationof adzuki beans resulted in a trade-off between yield and seed size. Cultivated adzuki beans have fewer but longer pods, fewer but larger seeds, a shorter stature, and also a smaller overall seed yield than wild forms.The exact place of domestication is not known;multiple domestication origins in East Asia have been suggested.
Seed remains of adzuki beans discovered in theCentral Highlandsof Japan were dated to c. 6,000–4,000 BP, and represent to date the oldest evidence for its cultivation, supporting an origin in Japan. Evidence suggests that "wild azuki bean have been domesticated and cultivated in Japan for over 10,000 years".
In Japan, the adzuki bean was one of the first crops subjected to scientificplant breeding.Important breeding traits are yield, pureness of the bean colour, and the maturing time.Separate cultivars with smaller seeds and higher biomass are bred forfodderproduction and asgreen manure.Locally adapted cultivars are available in China, Japan, Korea, and Taiwan.
More than 300 cultivars/landraces/breeding lines are registered in Japan.Largegermplasmcollections of adzuki bean are in China, at the Institute of Crop Germplasm Resources (CAAS),Beijing, with more than 3,700 accessions, and Japan, at the Tokachi Agricultural Experiment Station,Hokkaido, with about 2,500 accessions.
Weedforms of adzuki bean frequently occur in Japan. The wide spread of weed forms is due to adaptation to human-disturbed habitats, escapes of oldcultivars, and natural establishment from derivatives of hybrids between cultivars and wild forms.In contrast to wild forms, the weed forms of adzuki bean are used as a substitute for the cultivated form and consumed as sweet beans, especially if cultivated adzuki beans are attacked by pests. However, in cultivated gardens the weed form is recognized as contamination and lowers the seed quality of adzuki cultivars.
The nameadzukiis a transliteration of the Japaneseアヅキ, as it was spelled according tohistorical kana orthography. The namesazukiandadukireflect the modern pronunciationアズキ(hiragana:あずき). All are meant to represent the same Modern Japanese pronunciation,azuki.
Japanese also has a Chineseloanword,shōzu(小豆), which means "small bean", its counterpart "large bean"(大豆,daizu)being thesoybean. It is common to write小豆inkanjibut pronounce it asazukilisten, an example ofjukujikun. In China, the corresponding name (Chinese:小豆;pinyin:xiǎodòu) still is used in botanical or agricultural parlance. In everyday Chinese, the more common terms arehongdou(红豆;紅豆;hóngdòu) andchidou(赤豆;chìdòu), both meaning "red bean", because almost all Chinese cultivars are uniformly red.
In English the beans are often described as "red beans" in the context of Chinese cuisine, such as withred bean paste. In Korean, adzuki beans are calledpat(팥) and it contrasts withkong(콩, "bean"), rather than being considered a type of it.Kong("beans") without qualifiers usually meanssoybeans. In Vietnamese it is calledđậu đỏ(literally: red bean). In some parts of India, the beans are referred to as "red chori".InMarathi, it is known aslal chavali(लाल चवळी), literally meaning 'redcowpea'. In Iraq its name islūbyā ḥamrāˈ(لوبيا حمراء) meaning "red cowpeas".
The adzuki bean is mainly cultivated in China (670,000 hectares (1,700,000 acres)), Japan (60,000 hectares (150,000 acres)), South Korea (25,000 hectares (62,000 acres)), and Taiwan (15,000 hectares (37,000 acres)) (data published 2006).The bean is also grown commercially in the US, South America, India,New Zealand, Congo, and Angola.
In Japan, the adzuki bean is the second most importantlegumeafter thesoy bean. In 1998, the annual crop yield was around 100,000 tonnes (98,000 long tons; 110,000 short tons).In 2006, Japan consumed about 140,000 tonnes (140,000 long tons; 150,000 short tons)/year. Japan is the largest importer of adzuki beans.The imports come from China, Korea, Colombia, Taiwan, US, Thailand, and Canada.
Optimal temperature range for adzuki bean growth is between 15 and 30 °C (59 and 86 °F). The crop is not frost-hardy and needs soil temperatures above 6–10 °C (43–50 °F) (30–34 °C (86–93 °F) optimal) forgermination. Hot temperatures stimulate vegetative growth and are therefore less favorable for pea production.The adzuki bean is usually not irrigated. Annual rainfall ranges from 500 to 1,750 millimetres (20 to 69 in) in areas where the bean is grown. The plant can withstanddroughtbut severe reduction in yield is expected.The cultivation of the adzuki bean is possible on preferably well drained soils with pH 5–7.5.Fertilizer application differs widely depending on expected yield but is generally similar to soybean. Due to nodulation withrhizobia,nitrogen fixationof up to 100 kilograms per hectare (89 lb/acre) is possible.
The sowing of the peas is in 2–3 centimetres (0.79–1.18 in) depth in rows 30–90 centimetres (12–35 in) apart and 10–45 centimetres (3.9–17.7 in) within the row. Rarely seeds are sown by broadcast. The amount of seeds ranges between 8–70 kilograms per hectare (7.1–62.5 lb/acre). Growth of the crop is slow, thereforeweed controlis crucial mainly between germination and flowering. Cultivation systems differ largely among different countries. In China adzuki bean is often grown inintercropswith maize, sorghum and millet while in Japan the bean is grown incrop rotations. Harvest of the peas should not be done as long as moisture content of the seed is higher than 16%.
Fungal and bacterial diseases of the adzuki bean arepowdery mildew, brownstem rot, and bacterialblight. Furthermore, pests such as the adzuki pod worm, Japanese butterbur borer, andcutwormattack the crop. Thebean weevilis an importantstorage pest.
The description of the adzuki bean can vary between authors because there are both wildand cultivated formsof the plant. 
The adzuki bean is anannual,rarelybiennialbushy erect or twining herbusually between 30 and 90 centimetres (12 and 35 in) high.There exist climbing or prostrate forms of the plant.The stem is normally greenand sparselypilose.
The adzuki bean has ataproottype of root system that can reach a depth of 40–50 centimetres (16–20 in) from the point of seed germination.
The leaves of the adzuki bean aretrifoliate,pinnateand arranged alternately along the stem on a longpetiole.Leaflets are ovate and about 5–10 centimetres (2.0–3.9 in) long and 5–8 centimetres (2.0–3.1 in) wide.
Adzuki flowers arepapilionaceousand bright yellow.Theinflorescenceis an axillary falseracemeconsisting of sixto ten(two to twenty) flowers.
Adzuki pods are smooth, cylindrical and thin-walled.The colour of the pods is green turning white to grey as they mature.The size is between 5–13 by 0.5 centimetres (1.97 in–5.12 in × 0.20 in) with 2 to 14 seeds per pod.Pod shatterduring seed ripening and harvesting might be a difficulty under certain conditions.
The seeds are smooth and subcylindric with a length of 5.0–9.1 millimetres (0.20–0.36 in), width of 4.0–6.3 millimetres (0.16–0.25 in), thickness of 4.1–6.0 millimetres (0.16–0.24 in).The thousand kernel weight is between 50 and 200 g.There are many different seed colours from maroon to blue-black mottled with straw.
The emergence of the seedlings ishypogealand takes 7–20 days.Compared to other pulses the growth of the plant is slow.Normally the adzuki plant reaches maturity between 80 and 120 days depending on the cultivar and the environmental conditions.Floweringlasts 30–40 days.Commonly the plantself-pollinatesbutcross-pollinationalso exists.
InEast Asian cuisine, the adzuki bean is commonly sweetened before eating. In particular, it is often boiled with sugar, producing red bean paste, a very common ingredient in all of these cuisines. It is common to add flavoring to the bean paste, such as chestnut. Red bean paste is used in manyChinese dishes, such astangyuan,zongzi,mooncakes,baozi, andred bean ice.
It serves as a filling inJapanesesweets such asanpan,dorayaki,imagawayaki,manjū,monaka,anmitsu,taiyaki, anddaifuku. A more liquid version, using adzuki beans boiled with sugar and a pinch of salt, produces a sweet dish calledhong dou tang. Some East Asian cultures enjoy red bean paste as a filling or topping for various kinds of waffles, pastries, baked buns, or biscuits.
Adzuki beans are commonly eatensproutedor boiled in a hot,tea-like drink.
Traditionally in Japan, rice with adzuki beans (赤飯;sekihan) is cooked for auspicious occasions. Adzuki beans are used inamanattōandice creamwith the whole bean or as paste.
Cooked adzuki beans are 66% water, 25%carbohydrates, including 7%dietary fiber, 8%protein, and contain negligiblefat(table). In a 100-gram reference amount, cooked beans provide 536 kilojoules (128 kilocalories) offood energy, a moderate to high content (10% or more of theDaily Value, DV) of theB vitaminfolate(30% DV), and severaldietary minerals(11% to 27% DV, table).