Konjac

Amorphophallus konjac — konjac, konnyaku or devil's tongue — is a perennial herb in the arum family (Araceae), genus Amorphophallus, growing from a large flattened-spherical corm up to 25 cm across that may weigh several kilograms. Each year the plant produces a single huge leaf: its petiole is 0.5–1.5 m tall with brown-purple mottling, and the blade is three-parted then bipinnately divided, spreading up to 1.3 m with numerous ovate-elliptic leaflets. The inflorescence (appearing in the dry season, not with the leaf) consists of a dark purple-brown, bell- to oval-shaped spathe 20–60 cm long and a spadix up to 55 cm long bearing unisexual flowers — female flowers below, male flowers above — emitting a foul odour that attracts flies and beetles for pollination. The fruit is an orange-red berry in a spike with black, endosperm-less seeds. All parts — especially the corm — contain calcium-oxalate crystals that cause intense itching and burning of mouth and throat; the corm must be ground with alkaline ash or lime water and boiled to detoxify it before eating.

Updated by lebachungtdh@gmail.com · 10/12/2026

Konjac originates in southern China (Yunnan, Sichuan) and was domesticated about 2,000 years ago by the Yi people and other early cultivators; it is now grown throughout East and Southeast Asia (China, Japan, Korea, Taiwan, Indonesia, Vietnam). It prefers a warm, humid subtropical to tropical climate and grows beneath open forest and along moist ravines up to about 2,500 m; it is propagated by cormels, corm pieces, seed or tissue culture. The corms are harvested when the plant is dormant (winter–spring), peeled, ground with lime or ash water (calcium hydroxide) and boiled so that the glucomannan sets into a firm gel — in Japan known as konnyaku (white or black jelly) and the noodle shirataki, and in China as 'moyu' (魔芋豆腐), commonly eaten in hotpot, stir-fries and vegetarian dishes. Konjac flour and corm are rich in glucomannan, a water-soluble polysaccharide that absorbs water to form a gel and is largely indigestible, so it provides very few calories. Beyond food, konjac is used for konjac sponges, diet noodles, thickeners and the food additive E425. Glucomannan acts as a bulk laxative, promotes satiety and may help lower cholesterol and blood sugar; plenty of water must be taken with it because it can cause choking or oesophageal blockage, and the raw corm must never be eaten. The plant is also grown ornamentally for its unusual inflorescence.

Updated by lebachungtdh@gmail.com · 10/12/2026