Characterization of rheological properties of complex coacervates composed by whey protein isolate, chitosan and garlic essential oil

This work aims to study the effect of incorporation of garlic essential oil (GEO) with loading of 10% (GEO-10) and 20% (GEO-20) on the strength and stability of polyelectrolyte complex coacervate obtained by electrostatic interactions between chitosan (CH) and whey protein isolate (WPI) with positive and negative charges, respectively. Rheological studies were applied to investigate the viscosity and viscoelastic properties of complex coacervates. The viscoelastic properties were investigated by dynamic oscillatory tests and static tests (creep and recovery). The coacervates exhibited the shear-thinning behavior of non-Newtonian fluid, and the frequency sweep test revealed magnitude of elastic modulus (G′) higher than loss modulus (G″) at high frequency due to the formation of compact network structure with elastic dominant property (solid-like behavior). Arrhenius model was able to estimate the relationship between viscosity and temperature, and the high temperature caused molecular expansion and increase in intermolecular distances, leading to decrease on the viscosity. The energy of activation (Ea) was 25.24 and 20.74 kJ mol−1 for WPI/GEO-10/CH and WPI/GEO-20/CH, respectively. The highest Ea value for WPI/GEO-10/CH indicated the formation of more strength and structured network matrices for GEO protection. Creep and recovery data were well fitted by Burger model and exponential decay function, respectively, and obtaining R2 higher than 0.98. The percentage recovery (%R) was 16.67% and 9.52% for WPI/GEO-10/CH and WPI/GEO-20/CH, respectively, indicating that WPI/GEO-10/CH had greater capacity for structural recovery and the most suitable to be applied in food product that industrially requires large stress, high temperature and long-time processes.