Dangyuja - Citrus grandis

Species            Citrus grandis (L.) Osbeck

Origin  Korea

Dangyuja (당유자, Korean pronunciation: [taŋ.ju.dʑa]) is a Korean non-hybrid citrus fruit that is a specialty of Jeju Island. In Jeju language, it is called Daengyuji(댕유지; pronounced [tɛŋ.ju.dʑi]). Dangyuja has a similar shape and flavour to yuja, but is genealogically a variety of pomelo.

Dangyuja has been included in the Ark of Taste, an international catalogue of endangered heritage foods.

The evergreen broad-leaved tree grows to an average height of 6 metres (20 ft), with branches that have thorns on them, and the leaves are 10–13 centimetres (3.9–5.1 in) long. The fruit is 10–12 centimetres (3.9–4.7 in) long, 9–10 centimetres (3.5–3.9 in) wide, and usually weighs 300–500 grams (11–18 oz).

The colour of ripe fruit can range from dark yellow to yellow-orange. The rind is about 9 millimetres (0.35 in) thick, very fragrant, and slightly bitter, whil the flesh and juice is rich in sourness, and also with a unique fragrance.

Today, the fruit is used mainly for tea, dangyujacha, whose preparation is very similar to that of yujacha, "yuja tea". Back in the days dangyuja was often used in home remedies to prevent and treat common cold.

A soup called daengyujikkultang (literally "dangyuja honey tang"), was made of the crushed flesh of dangyuja, honey, and ginger. Cooked in the ashes of a fire, the mixture attains a thin syrup-like consistency. People used the cooled soup to treat cold.

Medicinal

In traditional Korean medicine, the fruit is used to treat various gastrointestinal ailments. Dongui Bogam, an encyclopaedic medical book published in 1613, writes that dangyujas can help detoxify and purify the stomach, treat alcohol intoxication, and stimulate a poor appetite.

Dangyuja is a citrus fruit of Cheju Island in Korea, which is known to have a high content of flavanone glycosides, such as naringin and neohesperidin. Flavanone glycosides of Dangyuja (Citrus grandis Osbeck) extract were converted into their aglycones by naringinase and hesperidinase, and into their hydroxylated forms by Aspergillus saitoi.

Dangyuja extract treated with A. saitoi had significantly higher antioxidant and antidiabetic activity than both its glycosides and aglycones in oxygen radical absorption capacity (ORAC) and supercoiled DNA strand scission assay, rat intestinal α-glucosidase and porcine pancreatic α-amylase inhibition, suggesting that the fermentation of flavanone aglycones of Dangyuja extract with A. saitoi can increase antioxidant and antidiabetic activity, compared to their glycosides and aglycones.

This result suggests that Dangyuja extract prepared with enzymatic and microbial treatments could be used for the development of pharmaceutical foods to control the blood glucose level of diabetic patients by inhibiting α-amylase and α-glucosidase in the intestinal tract.