pH and ionic strength induced complex coacervation of Pectin and Gelatin A

- Associative complex formation between pectin and Gelatin A for a range of pH and Gelatin concentration and ionic strength is discussed.
- Their interaction was characterized by the three signature pH transition values where observable change in the solution turbidity was noticed.
- Zeta potential profile provided information about the inter-polymer binding and binding ratio.
- Model calculations were done to understand the underlying interactions.

Study of Protein/Polysaccharide interactions aids to the better understanding of the specific and non-specific interactions known to occur between them. Herein, the inter-polymer complexation between Pectin (P) and Gelatin A(GA) was studied in a wide range of pHs (≈3-9) using zeta potential, turbidity titration and light scattering measurements in dilute aqueous solutions. This was characterized by the signature pH values where observable transitions took place, which are generally given as pHc(onset of binding), pHΦ (formation of soluble complex), and pHprep (formation of insoluble complex). In addition to this, the effect of ionic strength (I = 0-0.1 M NaCl) on the complex formation at different pectin to GA mixing ratio was probed. It was found that at pH < pI(≈9) GA electrostatic interactions were dominant while above pI such interactions were absent. However, addition of salt led to surface patch binding (SPB) at higher pH, and concentration of GA. A model calculation explained the potential energy of interactions between pectin and GA, and supported the experimental observations.

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