Abstract: In this study, water soluble dietary fiber from star anise (SASDF) was prepared by a microwave-assisted double enzymatic method and the effects of SASDF on the effective particle size, particle size distribution, zeta potential, apparent shear viscosity and microstructure of protein-coated nano-emulsion before and after digestion were studied. Its effect on the digestive properties was also studied by in vitro digestion model. The results showed that SASDF had a significant effect on the physicochemical and digestive properties of the emulsion before and after digestion in a concentration-dependent manner. The digestion curves of the nano-emulsion showed a second-order pseudo first-order reaction irrespective of the presence of SASDF. The reaction rate constant k1 in the rapid reaction stage decreased with the increase of SASDF concentration, while in the slow reaction stage, the reaction rate constant k2 showed no correlation with SASDF concentration. However, the final digestibility of fat in the nano-emulsion decreased with the increase of SASDF concentration in the system.

Key words: star anise; water soluble dietary fiber; lipid digestion; emulsion