Longan is a genus of longan in the family Anasapinaceae, also known as laurel and lychee. Longan is named because of its round black and shiny species, and the umbilical protrusions are white, resembling the eyes of the legendary "dragon". The history of longan cultivation dates back more than 2,000 years to the Han Dynasty. Northern Wei (386-534) Jia Sixun's "Qi Min Zhishu" Yun: "Longyan is a puzzle and a bime." "Because it matures in the season when the laurel tree is fragrant, it is commonly known as guiyuan, and it was listed as an important tribute in ancient times. Emperor Wen of Wei (535-551) once issued an edict to his courtiers: "The treasures of the southern fruit, there are dragon's eyes and lychees, and the years are tribute." ”
Longan is native to the southern part of the mainland, and is distributed in Fujian, Taiwan, Guangdong, Guangxi, Sichuan, Guizhou, Yunnan and other places on the mainland. Among them, Fujian's output accounts for 50% of the country's total output.
Each 100g of longan pulp contains 12% ~ 23% of total sugar, 26.91% of glucose, 1.26% of tartaric acid, 1.41% of protein, 0.45% of fat, vitamin C 163.7mg, vitamin K 196.6mg, vitamin B1, vitamin B2, vitamin P, etc., after processing to produce dry results, sugar per 100g 74.6g, iron 35mg, calcium 2mg, phosphorus 110mg, potassium 1200mg and other minerals, as well as a variety of amino acids, saponins , X-glycine, tannin, choline, etc., which are the source of its powerful tonic power.
Fresh longan requires freshness, moderate ripeness, large flesh and thick flesh, thin skin and small core, juicy taste, complete shell, and undiminished color. The method of identifying maturity is as follows.
Look at the color. The shell is yellowish brown, slightly bluish, moderately ripe; If the husk is mostly blue, the ripeness is insufficient.
Touch it with your hands. Pinch the fruit with 3 fingers, if the shell is hard, it is a fruit; Such as soft and elastic, is a mature characteristic; Soft and inelastic, it is overripe and about to deteriorate.
Look at the pits. Peel off the husk, if the flesh is white, easy to leave the pit, the kernel is black, indicating that the ripening is suitable; The flesh is not easy to peel, and the pit is reddish, indicating that the fruit is partial and the flavor is light.
Longan is more suitable for refrigeration and storage in an environment of 4~6 °C, like animal hibernation, at this temperature, longan has life to breathe, but consumes very little energy. It cannot be stored in a sealed plastic bag, but a mesh plastic bag should be used to facilitate its breathing. If you don't have a mesh bag in your home, you can punch a few holes in the crisper bag. With this method, fresh longan can be stored for about 15 days. If you rely on professional freezing methods, you can keep longan for about 3 months, but the taste will be slightly worse. You can take fresh longan to dry and store it. Sun-dried longan is stored for a long time, and it will also have a special flavor, should be placed in a box, covered with plastic, and then placed in a cool place, to check frequently, to prevent mold, insects, etc.