The extraction process of gelatine from hides and skins consists of several steps. Native collagen is a highly structured protein which is insoluble in water. For this reason, a pre-treatment is necessary in order to break such structure, produce fibre swelling and collagen solubilisation, thus enabling its further extraction. An acid pre-treatment is commonly used when gelatine is extracted from pig skins. An alkaline pre-treatment is performed when bovine hides are used as a raw material. After this treatment (a long process that takes several weeks), the treated material is washed free of alkali and neutralised by the addition of acid. Most of the neutral salts produced during this process are then removed by numerous washes. As a result, this is a process with a high water requirement which also generates highly protein-content wastewater. For this reason, an improvement of the process which leads to savings in energy and water consumption is regarded of high priority.
Proteolytic enzymes (proteases) are commonly used in the detergent industry for breaking down proteinaceous matter caused by body secretions, food stuff, and blood. Such type of enzymes is also being introduced in the leather industry as an alternative to conventional procedures in dehairing, bating and soaking processes.
The use of this kind of enzymes during the pre-treatment of hides prior to gelatine extraction has been proposed within LIFE microTAN project as a new enzymatic pre-treatment, alternative to the alkaline and acid ones, in order to minimise the environmental impact, as well as to reduce processing time.
A scheme of the proposed procedure, as carried out at laboratory scale, is shown in the picture below.