1. Hair removal(epilation)，Degreasing，Washing
Dry skin of cattle or pig should be soaked in water until it is swollen. The epidermis and fatty layer are removed to leave the middle collagen-rich part. If it is fatty skin, such as pigskin, a degreasing machine can be used to remove the fat with hot water and mechanical force. Most of the dirt, fat, fur on the skin will be eliminate after this process.
2. Acid pretreatment for type A gelatin
Add hydrochloric acid and soak for 1-2 days at temperature of 10-20°C and pH of 2.5-3. Keep stirring so that the acid can fully contact with skin. Wash off excess acid and impurities with water after soaking.
3. Extraction
The partially hydrolyzed collagen is usually heated to extract gelatin by a stepwise heating method. Heat the skin in weak acid or neutral water at 50°C for 4-6 hours and the solution is released when its concentration reaches to 3%~8%. Increase the temperature 5~10°C each time and repeat previous step until boiling. The collagen is continuously decomposed into water soluble peptides from outside to inside. The higher temperature, the longer heating time and the lower pH, the more collagen will be hydrolyzed and vice versa.
4. Filtration
The gelatin solution drained from the heating tank was filtered to remove large granulated impurities. This crude filtered solution will be filtered several times to obtain crystal gelatin granules.
Cellulose based filtration: The pressurized gelatin solution goes through the multi-layer cellulose fibers by which the visible particles will be adsorbed. Sometimes the diatomaceous earth is utilized to adsorb smaller particles.
Ion Exchange: Gelatin solution also contains various anions and metal cations after cellulose filtration. They will precipitate in concentrated solution to reduce clarity, sometimes the gelatin even becomes turbid. The ion exchanger can trap cations and anions and release hydrogen ions and hydroxide ions into solution.
Membrane filtration: The extremely small pores in membrane can only allow water, ions, and small-mass impurities to pass through, while the large molecular gelatin will be blocked. After this process, the concentration increases to 10%.
5. Evaporation and Sterilization
The filtered solution needs to enter a multi-effect vacuum evaporator to eliminate some water. Large multi-layer plates and low pressure allow water to evaporate rapidly at lower temperatures, stopping excessive hydrolysis. The concentration is around 30% after evaporation and it needs to be sterilized: the gelatin solution is heated for 4s at 140°C by hot steam.
6. Band dryer
Concentrated gelatin solution is extruded like noodles after being cooled. These strips are shredded to fed into band dryer and they are dried by hot air that gradually becomes hotter. Then they are ground by machine to make semi-finished small granules or powder. Their moisture content is 10-13%.
7.Blending，package and storage
Each batch of gelatin has different parameters. In order to obtain a standardized product, it is necessary to evenly mix them in a certain ratio. It is packed in a waterproof bag and stored in a cool and dry place. 25kg per bag