Adzuki bean

Adzuki is a bushy, annual climbing legume that grows to about half a metre or more, with trifoliate leaves, yellow flowers and slender pods of about 5 to 12 cm. Each pod holds a handful of small, oblong beans around 5 mm long, usually a glossy dark red with a pale ridge along one side. Black, white and mottled forms also exist.

Cooked adzuki beans are tender and mildly sweet with a nutty, earthy flavour and a pleasantly mealy texture. They are sold dried and whole, canned, sweetened and mashed as anko paste, ground into flour, and as sprouting seed. Dried beans cook faster than many larger pulses.

Adzuki is thought to have been domesticated in East Asia, with evidence pointing to the region of China, Japan and Korea, where archaeological finds in Japan date back several thousand years. Its wild ancestor, Vigna angularis var. nipponensis, still grows in parts of East Asia and the Himalayan foothills.

The English name comes from Japanese azuki, written with characters meaning small bean. The name aduki is a spelling variant, and in Chinese it is called hong dou, red bean. Today the crop is grown mainly in China, Japan, Korea and Taiwan.

Adzuki has been cultivated in East Asia for millennia and became a cornerstone of regional cuisine and ritual. In Japan, the red colour is linked with luck and warding off evil, which is why red beans are cooked with glutinous rice for sekihan at celebrations. Sweetened bean paste, anko, became the foundation of wagashi confectionery, including mochi, dorayaki, yokan and taiyaki, and Hokkaido grew into the country's main production region.

In China, red bean soup and sweet buns are traditional, and in Korea, adzuki is used in patjuk porridge eaten on the winter solstice and in pat-bingsu shaved ice. Taiwan and Southeast Asia have added red beans to shaved ice and drinks.

Outside Asia, adzuki spread in the 20th century through natural foods and macrobiotic diets, and then through Japanese restaurants. It is grown commercially in several countries, including parts of North America and Oceania, mainly for export to Japan and the health-food trade.

Adzuki beans are simmered and sweetened for anko, red bean soup, ice cream, buns, mochi fillings, ice desserts and pastries. They are also cooked into savoury rice dishes, stews and salads, ground into flour, and sprouted for salads and stir-fries.

Traditionally they are used in Chinese herbal and food therapies. The dry beans are also used as filling in heat packs and, historically, as small counters. Dried beans are also stuffed into hand warmers and cushions in some Asian households, and young sprouts are added to salads and soups for crunch.

Adzuki beans are a good source of plant protein, fibre, folate, potassium and iron, and like other pulses they are linked with healthy diets and steady blood sugar response. Laboratory studies on their polyphenols are interesting but human evidence is limited. Commercial red bean desserts are often high in sugar, which offsets benefits.