Enzymes in Wet Blue Processing

Leather processing is divided into two stages:

Wet blue processing involves steps like fleshing, soaking, dehairing, liming, bating, pickling, tanning and sammying.

The leather industry is more traditional and new enzyme applications are slowly catching on, though bating with enzymes is a long-established application. One of the prime roles of enzymes is to improve the quality of leather, but they also help to reduce waste. This industry, like many others, is facing tougher and tougher environmental regulations in many parts of the world. The consumption of chemicals and the impact on the environment can be minimised with the use of enzymes. Even chrome shavings can be treated with enzymes and recycled.

Over year's of research AETL has developed enzyme based products for lime free and sulphide free processing. Products can be applied in beam house processing or wet blue processing successfully with equal cost effectiveness.

Soaking

Restoration of the water of salted stock is a process that traditionally applied surfactants of more or less biodegradability. Alkaline Proteases, with a pH optimum around 9-10, are now widely used to clean the stock and facilitate the water uptake of the hide or skin. The enzyme breaks down soluble proteins inside the matrix, thus facilitating the removal of salt and hyaluronic acid. This makes room for the water. Lipases provide synergy. SEBSoak is highly effective enzyme from AETL for soaking application.

Liming

Alkaline proteases and Lipases, branded as SEBLime from AETL are used in this process as liming auxiliaries to speed up the reactions of the chemicals normally used. For example, the enzymes join forces to break down fat and proteinaceous matter such as dermatan sulphate, thus facilitating the opening up of the structure and the removal of hair. The result is a clean and relaxed pelt that is ready for the next processing step.

Acid bating

Pickled skins and wet-blue stock have become important commodities. A secondary bating is necessary due to nonhomogeneity. For skins as well as double face and fur that have not been limed and bated, a combination of an acid protease and lipase or Acid Bate / SEBate Series from AETL ensures increased evenness, softness and uniformity in the dyeing process. Wetblue intended for shoe uppers is treated with a semi-acid protease combined with a lipase, resulting in improved consistency of the stock.

Degreasing/fat dispersion

Lipases offer the tanner two advantages over solvents or surfactants: improved fat dispersion and production of waterproof and low-fogging leathers. Alkaline lipases are applied during soaking and/or liming, preferably in combination with the relevant protease. Among other things, the protease opens up the membranes surrounding the fat cell, making the fat accessible to the lipase. The fat becomes more mobile and the breakdown products emulsify the intact fat, which will then distribute itself throughout the pelt so that in many cases a proper degreasing with surfactants will not be necessary. This facilitates the production of waterproof and low-fogging stock. Lipases can also be applied in an acid process, e.g. for pickled skin or wool-on and fur, or a semi-acid process for wetblue.

Not many companies offer this solution by enzymatic way. AETL is one of the few companies offering degreasing enzyme - SEBDegrease successfully.

Wet blue is the intermediate stage of leather processing. The wet-blue hides have been tanned and can be stored or transported from the tannery to finishing plants around the world.