Grass jelly is a famous product of Lang Son province. The origin of the Lang Son grass jelly tree has not been identified through any documents, however, this type of tree has been cultivated by the people of Lang Son and developed in three districts of Trang Dinh, Van Lang, and Binh Gia since the 70s of the last century. Moreover, the grass jelly tree is considered as an indigenous, traditional tree with local economic value.

Lang Son grass jelly is consumed in the domestic market from North to South in the form of products such as dried grass jelly, instant grass jelly, and grass jelly powder. In addition, Lang Son dried grass jelly and grass jelly powder are exported to many countries, namely China, Taiwan, Thailand, Laos, Malaysia, India, the USA, and Korea.

According to havesters, trading facilities, and import and export enterprises of dried black jelly, Lang Son black jelly is purchased and distributed more preferable due to the different quality compared to other localities, which is the content of antagonism in Lang Son grass jelly tree is large, the ratio of leaves on the wall is high.

 Lang Son dried grass jelly tree has a large number of leaves on the stem, and high viscosity when soaked. The high leaf-to-stem ratio ensures that Lang Son instant grass jelly has a distinct aroma and a crunchy, chewy taste with little water separation. The pectin content in Lang Son dried grass jelly is from 27.86% - 31.06%, and in Lang Son instant grass jelly tree from 15.45% - 17.31%. Lang Son grass jelly powder has a Pectin content of 39.75% - 40.60%.

Lang Son grass jelly has unique properties and quality due to the relationship between natural geographical conditions and the traditional production methods of the people here.

In Lang Son, the grass jelly tree is grown on soil with a sand density of 53.17 ± 9.95%. Due to the high sand content, the soil for growing grass jelly trees in Lang Son has great porosity, large opening size, helps the soil to absorb water quickly, has good drainage, and has high aeration. This is consistent with the biological characteristics of the grass jelly tree which is moisture-loving and sensitive to waterlogging due to its clustered roots. The pectin content in grass jelly trees has a positive influence on the calcium (Ca2+) content in the soil. The content of Ca2+ in the soil growing grass jelly tree in Lang Son is 12.52 ± 4.97 cmol/kg, which is higher than that of Hau Giang and Lam Dong, which explains why the Pectin content in Lang Son grass jelly tree is higher.

In addition, the specific quality of Lang Son’s grass jelly is also influenced by the production skills of the locals.

Accordingly, the farming method used by the people changes depending on the topographical conditions. For the upland, people plant grass jelly tree in the streamside area where there is a gentle slope (<25°) due to the moisture retention and good drainage of the soil here. In the field, grass jelly tree is grown in an area with a bed width of about 1.0 - 1.5m based on the experience of the people, wider beds make plants more susceptible to death and narrower beds are laborious and take up space. When the field is dry, water is slowly led into the field, the water just fills the bed surface and stays in the field for about 2-3 hours, and remove immediately afterward to avoid too much moisture in the soil, causing the plant to rot.

During the harvest season, (about 110 - 130 days after planting), people only collect the fruit of their labor when the top leaves begin to roll, avoiding harvesting when the tree has fully blossomed. When harvesting, people use sharp knives and sickles to cut close to the root. Stems and leaves are spread in the sun for a day, then covered with canvas and composted in piles for 1-2 days. When the leaves turn black, the grass jelly tree is continued to dry for another 1-2 days until dry. This harvesting method ensures the best quality of dried grass jelly trees, which is an important ingredient in the production of instant grass jelly and grass jelly powder.

The processing of instant grass jelly is divided into two stages. The first is to process pure grass jelly solution by cooking the harvested dried grass jelly with water for about 4-5 hours at a ratio of about 1/12. After obtaining, the grass jelly solution is further cooked with additives (sugar, rice flour, or tapioca) and water according to the ratio of grass jelly solution of about 70 - 80% and additives of about 20 - 30. %, the amount of clean water is about 15-20 liters. The process stops the jelly is thick and easy to pour, and the color changes to cockroach wings when viewed under the light. This technique helps the cooks in Lang Son obtain the maximum amount of pure grass jelly tree solution and the appropriate grass jelly solution/additive ratio will make the jelly firm, crispy, tough, less water separated, has a characteristic aroma, and a cool taste.

During the processing of grass jelly powder, besides ensuring the input material, Lang Son dried grass jelly tree, the technique of extraction and removal of residue to recover grass jelly tree is important. Accordingly, the ratio of dry grass jelly tree (kg)/water (liter) when extracted is about 1/20. Practical experience of the manufacturer shows that the jelly structure is more friable, the shape is easily changed, the color is light, the taste is reduced and the pectin content in the grass jelly is low, not enough to create the consistency, brittleness, and toughness when increasing the water; and when reducing water, the grass jelly increases the bitterness. In addition, in the extraction process, based on the experience of longtime jelly cooks or built-in equipment in the pot, a controlled temperature between 110 - 115oC is the optimal temperature. Temperatures higher than the optimum temperature will cause the pectin to denature, the solution to become more liquid, and reduce the viscosity. The control of extraction time (about 8-10 hours) is also an important factor to ensure the quality of grass jelly. Based on the experience of grass jelly powder manufacturers, increasing extraction time will reduce extraction efficiency. This is because, with high-temperature conditions and a long time, Pectin will be decomposed.

Geographical area: Cao Minh commune, Doan Ket commune, Khanh Long commune, Tan Yen commune, Vinh Tien commune, Chi Lang commune, De Tham commune, Dai Dong commune, Hung Son commune, Khang Chien commune, Chi Minh commune, etc. Tan Tien, Kim Dong commune, Tri Phuong commune, Quoc Khanh commune, Doi Can commune, Tan Minh commune, Trung Thanh commune, Dao Vien commune, Quoc Viet commune, Hung Viet commune and That Khe town in Trang Dinh district; Bac Hung commune, Bac Viet commune, Bac La commune, Gia Mien commune, Hoang Viet commune, Hoi Hoan commune, Hong Thai commune, Thuy Hung commune, Trung Khanh commune, Tan Tac commune, Thanh Hoa commune, Hoang Van Thu commune Tan My, Tan Thanh commune, Thanh Long commune, Nhac Ky commune and Na Sam town in Van Lang district; Hoang Van Thu commune, Tan Van commune, Minh Khai commune, Hong Phong commune, Hong Thai commune, Binh La commune, Hoa Tham commune, Quy Hoa commune, Vinh Yen commune, Hung Dao commune, Quang Trung commune, Mong An commune, commune Thien Thuat, Hoa Binh commune, Yen Lo commune, Thien Hoa commune, Tan Hoa commune, Thien Long commune and Binh Gia town in Binh Gia district, Lang Son province.

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