Abstract: In this paper, microcapsules were prepared by complex coacervation method using gelatin (G) combined with arabic gum (GA), pectin (P) or sodium hydromethyl cellulose as the wall material and green coffee oil as the core material. The effects of the three wall material combinations on the morphology, moisture, yield, microencapsulation efficiency, particle size and structure of green coffee oil microcapsules were studied. Results showed that the as-prepared empty microcapsules and green coffee oil microcapsules were?spherical?and?intact with uniform distribution under optical microscopy and revealed yields and microencapsulation efficiencies of 90.0% and 85.0%, respectively, but they had different utilization rates of wall materials, with the highest value being observed for G/P combination (76.6%). Fourier transform infrared spectroscopic (FTIR) analysis confirmed that the interaction between gelatin and each of the polysaccharides was through electrostatic interaction rather than chemical interaction. The condensation reaction only took place between the wall materials, and no other chemical reaction occurred between the core material and the wall materials. The curve-fitting of amide I bands in the FTIR spectra demonstrated that the relative contents of β-sheet and random coil in the coacervates were reduced, whereas the relative contents of α-helix and β-turn were increased. Thermal gravimetric analysis revealed that the thermal stability of the complexes was related to that of the wall materials, and the gelatin/sodium carboxymethyl cellulose (CMC) complex had the best thermal stability; microencapsulation with this wall material significantly increased the thermal stability of coffee oil. This study can supply a theoretical basis and technical support for high-valued application of green coffee oil.

Key words: microcapsule; complex coacervation; gelatin; polysaccharides; green coffee oil