Complex coacervation between lysozyme and pectin: Effect of pH, salt, and biopolymer ratio

The complexation between lysozyme and pectin was studied by acidification using zeta potential, turbidity measurements and calorimetry titration. The complexes were analyzed in various NaCl concentrations with different ratios. At ratio 1:1 with 0.01 M NaCl, is worth mentioning that the insoluble complexes were formed between pH 2.0 and 7.0, which represents a great range to apply this complex to different food matrices. When the ratio was increased from 1:1 to 3:1, the pH range between the pH(phi 1) and pH(phi 2) increased even more. When the NaCl concentration was increased from 0.01 M to 0.2 M, a progressive reduction of turbidity was observed. At 0.4 M NaCl, there was total suppression of complex formation at ratio <= 3:1. The process of complex coacervate formation occurred in two different steps, presenting favorable enthalpic as well as entropic contributions. The positive entropy change is a strong indication that water molecules have been released from the complex surface, however the positive sign of T Delta S suggests that hydrophobic interactions were involved in the interaction between Iysozyme and pectin. Microscopy images of the samples revealed that the complexes presented a spheroid-like appearance which may contribute to possible future applications. (C) 2017 Elsevier B.V. All rights reserved.