Turtle shell glue, also known as turtle glue or turtle shell paste, is a solid block of glue made from the shells of turtles, such as Chinemys reevesii (Gray). According to the book "Ben Cao Sui Yuan", the preparation involves boiling the cleaned turtle shells multiple times until the gelatin is extracted. The extract is then filtered, and a small amount of alum powder is added to the filtrate. After settling, the clear glue is collected and simmered until it thickens into a paste. It is then poured into a mold to solidify, cut into small pieces, and dried in the shade.
In the processing method mentioned in "Jing Yue Quan Shu", the turtle shell is chopped and stir-fried into small beads. According to "Ben Cao Hai Li", it should be ground into a very fine powder. Nowadays, turtle shell glue is softened by gentle heating and cut into small squares or crushed when used.
The appearance of turtle shell glue is usually rectangular or square-shaped, flat, or in small or crushed pieces. It has a brownish-green color with slight transparency, resembling clean amber. The texture is hard and brittle, with a faint fishy smell and a mild taste.
Turtle shell glue has a sweet and astringent taste, and it is neutral in nature. It belongs to the liver and kidney meridians. It is known for its nourishing yin, replenishing blood, and hemostatic properties. It is used for conditions such as yin deficiency and blood deficiency, bone-steaming and overwork heat, night sweats, restlessness and palpitations, kidney deficiency and back pain, weakness and atrophy of the legs and knees, vomiting blood, nosebleeds, excessive menstruation or abnormal vaginal discharge. It is also used in combination with cinnamon and white atractylodes to treat persistent fever and malaria (according to "Ben Cao Hui Yan").
In terms of processing research, the Ming Dynasty recorded the methods of chopping and stir-frying turtle shell glue. In the Qing Dynasty, it was required to be ground into a very fine powder, and methods such as stir-frying with clam powder ("Yi Zong Jin Jian") and stir-frying with oyster powder ("De Pei Ben Cao") were introduced. Nowadays, it is softened by gentle heating or stir-fried before use.
According to reports, a new production process for turtle shell glue includes the following steps: raw materials → rinsing → steaming and pressurized extraction → separation and sedimentation → concentration → foam removal → gelation → cutting. Compared with traditional methods, the new process adds a semi-settling step to enhance the removal of impurities. It replaces the traditional atmospheric extraction with steam and pressure extraction, which is conducted under high temperature and pressure conditions to facilitate the extraction of collagen. This results in a higher gelatin yield, 4.19% higher than traditional methods. The new process also has advantages such as lower labor intensity, improved efficiency, and reduced environmental pollution.
