Modelling the charge across pH and isoelectricpoint of bovine collagen during leather manufacture

Andrew Ballantyne*, Stefan Davis

*Corresponding author for this work

Research output: Contribution to ConferencePaper


Many areas of leather production rely heavily on the manipulation of acidic and basic residues within the primary collagen structure to vary the overall charge of the substrate. For example, it is the basis which enables swelling during liming, deswelling during deliming, penetration of chromium after addition of chrome tanning salts and the fixing of chrome to carboxylate residues during basification. Manipulation of the charge on collagen is readily achieved through the addition of acids or bases into the float which may react with these residues to alter the charge.

Often, the increase in anionic charge and reduction in cationic charge with increasing pH are shown to happen concurrently and linearly with the iso-electric point (IEP) given as the point at which the positive and negative charges present on the collagen are equal. However, the pH at which carboxylate / acid groups undergo protonation / deprotonation is significantly lower than that at which an amine / ammonium is protonated / deprotonated, meaning the linear model described above is not a true representation of charge of collagen at varying pH.

Here we model the charge of a collagen substrate based off the amino acid profile of bovine skin, considering their relative levels within the collagen and concentrations within a water / collagen matrix, representative for collagen saturated with water. Models are presented for raw and limed bovine hides. This broader approach enables greater understanding of the influence of charge on the collagen substrate compared to IEP on its own, revealing contrasting charge profiles in acidic and alkaline regions of raw collagen, providing greater understanding of their differing behaviour during alkali swelling.
Original languageEnglish
Number of pages10
Publication statusPublished - Jul 2019
EventIULTCS Congress 2019: "Benign by design" - Leather, the future through science and technology - Dresden, Germany
Duration: 25 Jun 201928 Jun 2019
Conference number: XXXV


ConferenceIULTCS Congress 2019
Internet address


  • leather
  • leather manufacture
  • modelling
  • pH


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