Mixed aqueous chitin nanocrystal–whey protein dispersions: Microstructure and rheological behaviour

Chitin nanocrystals (ChN) and whey protein isolate (WPI) aqueous dispersions (at pH 3.0) of different polymer concentrations were mixed and examined with small deformation oscillatory measurements and polarized optical microscopy, under different conditions of ionic strength and temperature. The ChN–WPI mixed dispersions displayed a gel-like behaviour with increasing either the ChN or the WPI concentration. The network formation could be attributed to phase separation phenomena, as evidenced by the micrographs obtained, due to thermodynamic incompatibility between the two components; i.e. the addition of WPI, as a globular biopolymer mixture, in a dispersion of rod-like particles (ChN) leads to the formation of ChN-rich and ChN-poor domains. Increasing ionic strength did not significantly affect the viscoelastic properties of the network. However, heating of the ChN–WPI mixed dispersions resulted in further increase of the elastic modulus, which was irreversible upon cooling.