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In this work, the stability of CP-TA complex stabilized emulsion was first characterized. It was found that the peak thickness, Turbiscan Stability Index (TSI) and droplet size of CP-TA complex stabilized emulsion gradually decreased with increasing content of TA, indicating the gradually enhanced physical stability of emulsion, which was attributed to the gradually decreased interfacial tension, zeta potential and increased viscosity of CP-TA complex. Moreover, the oxidative stability of CP-TA complex stabilized emulsion gradually enhanced with increasing of TA content due to the antioxidant activity of TA. XRD and FTIR results suggested that the interaction between CP and TA gradually enhanced with increasing content of TA in CP-TA complex, leading to the formation of larger CP-TA clusters shown in AFM results. In conclusion, the presence of tannic acid (TA) enhanced the physical and oxidative stability of chitin particles-tannic acid (CP-TA) complex stabilized oil in water emulsion., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The spectroscopy and thermodynamics method was applied to study the binding of tannic acid (TA) to sodium caseinate (SC) in a phosphate buffer solution at pH 7.0. The turbidity of TA/SC complexes in phosphate buffer solution increased with increasing of TA/SC mass ratio. It tended to equilibrium until the TA/SC mass ratio was over the value of 1:1. The presence of TA changed the particle size of TA/SC complexes, which decreased with increasing of TA/SC mass ratio (TA/SC mass ratio less than 1:1). The intrinsic fluorescence and synchronous fluorescence spectra measurements demonstrated the complexes of SC with TA, which leads to the formation of TA/SC complexes. The far-UV CD results indicated that the TA induced a progressive increased in proportion of β-sheet structure, however, the proportion of α-helical, β-turn and random coil all decreased. Fourier transform infrared spectroscopy (FTIR) further confirmed that TA induced the transformation of SC structure. Isothermal titration calorimetry (ITC) measurements, which were used to characterize the binding mechanism of TA/SC complexes in phosphate buffer solution (pH 7.0) at 25 °C, clearly showed that the binding between TA and SC was mainly driven by the noncovalent interaction (e.g. H-bonding). [ABSTRACT FROM AUTHOR]

• CP (chitin particles) and TA(tannic acid) interacted intensely in solution. • There was synergistic effect for CP and TA in stabilizing oil in water emulsion. • CP-TA (3/5) complex stabilized emulsion had the best physical and oxidative stability. • CP-TA (3/5) complex had the lowest interfacial tension and zeta potential. • CP-TA (3/5) complex had the highest viscosity. The aim of the present study was to explore the effect of CP and TA on stability of oil in water emulsion stabilized by the two components, so as to fabricate the most efficient chitin based emulsifying agents. It was found that there was synergistic effect for CP and TA in stabilizing emulsion, specifically, the complex of chitin particles (CP) (3 g/L) with tannic acid (TA) (2 g/L) produced the most physically and oxidatively stable oil-in-water emulsion compared with other groups in this study. This is because CP-TA (3/5) complex had the lowest zeta potential, the lowest the oil water interfacial tension, the highest viscosity and the highest content of TA with excellent antioxidant activity. Furthermore, this is because there was intense interaction between CP and TA in CP-TA complex from results of FTIR, XRD and ITC, which then result in the formation of large CP-TA particles. [ABSTRACT FROM AUTHOR]