LPT 312: Abattoir Practices and Animal Products Technology (1+1)

CONDITIONING OF HIDES AND SKINS

• The preserved hides and skins are first conditioned at the tanneries before tanning under the following steps:
• Washing and soaking:
  • It is done for several hours in water containing zinc chloride and a mix of soda ash and borax.
  • During this process, salt is removed along with proteins of blood and lymph.
  • The hides absorb water and restore their original shape and dimension.
• Fleshing:
  • It is done on a convex wooden beam by scrapping the flesh with a serrated knife.
• Liming and dehairing:
  • A saturated solution of lime and 0.1% sodium sulphide remove and loosen hair and epidermal cells.
• Washing and deliming:
  • The hides are now washed with weak acid to neutralize the lime.
  • A mild heat can also be used if necessary.
• Bating:
  • The hides are treated with proteolytic enzymes (pancreatic juice mixed with saw dust) at pH 8.5.
  • It results in soft and pliable pelt, which can be tanned by vegetable tanning.
• Pickling:
  • It is done for chrome tanning wherein pelts are pickled in a bath of 1% sulphuric acid and 10% salt in water at pH of 2 to 2.5 for 2 to 3 hours.