Effects of salt and protein concentrations on the association and dissociation of ovalbumin-pectin complexes

• Formation of ovalbumin-pectin coacervate complexes was analyzed.
• Changes in protein concentrations led to shifts in the region of insoluble complex formation.
• XRD of the ovalbumin-pectin coacervate complex showed a partially defined crystalline region.
• Effect of ovalbumin self-aggregates on ovalbumin-pectin complex formation was analyzed.

Formation of ovalbumin-pectin coacervate complexes was analyzed in various NaCl concentrations and with various protein:polysaccharide ratios by isothermal titration calorimetry (ITC), by measuring zeta (ζ)-potentials, and by X-ray diffraction. The titration curve of a 1:1 ovalbumin:pectin coacervate complex formed in 0.01 M NaCl displayed a region containing insoluble complexes, a region of considerable complex formation, and a region of complex dissociation. Changes in protein concentrations led to shifts in the region of insoluble complex formation (at the isoelectric point). At an ovalbumin:pectin ratio of 8:1, complex formation was suppressed. At NaCl concentrations of 0.05 and 0.1 M, ovalbumin self-aggregation increased. When NaCl concentrations increased from 0.1 to 0.4 M, complex dissociation was suppressed. X-ray diffraction of the ovalbumin-pectin coacervate complex showed a partially defined crystalline region from 27 to 20° suggesting that the structure of the complex is more organized than the individual amorphous polymers. Finally, this study addressed the effect of ovalbumin self-aggregates on ovalbumin-pectin complex formation.

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