| This study takes the defatted star anise as the material,uses microwave-assisted enzymic technology to investigate the optimum processing conditions of star anise water soluble dietary fiber（SASDF）.The composition,physicochemical properties and functional properties of SASDF obtained under the optimum process conditions were determined.The effects of SASDF on the physical and chemical properties and digestion characteristics of emulsion oil were studied before and after the treatment of small intestine model by pH-stat method.This study can provide theoretical basis for the application of SASDF in the food and feed industry.It was found that the preparation of SASDF by microwave-assisted method has the advantages of high extraction rate and short extraction time.It was found that the ratio of material to liquid,papain extraction time,saccharification enzyme extraction time and microwave power had a great influence on the extraction rate of SASDF.The orthogonal optimization results are as follows:The order of the four factors affecting the extraction rate of SASDF was:saccharification enzyme extraction times>protease extraction times>microwave power>material-liquid ratio;the best process was:solid-liquid ratio 1:40,microwave power 500 W,papain dosage 2%,glucoamylase dosage 4%,papain extraction time 3×20 s（extract 3 times,20 s each time,interval 2 min）,glucoamylase extraction time was 5×20 s（extract 5 times,20 s each time,2 min intervals）,and the optimal extraction rate was 7.89%.The routine nutritional components of SASDF:protein 0.66±0.013%,moisture content10.88±0.5%,ash content 7.57±0.63%.The Neutral sugar content of SASDF:rhamnose 2.67%,arabinose 5.77%,galactose 8.92%,glucose 0.49%,xylose 5.6%.The SASDF contains 52.02%galacturonic acid with an esterification degree of 50.9%,indicating that it is a low ester pectin.It’s weight average molecular weight（88kDA）was smaller and more concentrated than that of apple,orange peel and beet pectin.The oil adsorption performance of SASDF was significantly better than that of inulin.For SASDF itself,the adsorption capacity of SASDF for saturated oil is significantly stronger than its adsorption capacity for unsaturated oil.The cholesterol adsorption capacity of SASDF was significantly better than that of inulin in simulated stomach and small intestine.The adsorption capacity of SASDF for cholesterol in the simulated small intestine is stronger than that in the stomach.As for the adsorption capacity of sodium cholate,SASDF is significantly stronger than inulin.At 1000 times magnification,the honeycomb structure of SASDF surface can be observed,while the inulin surface is relatively smooth.SASDF also has better cation exchange capacity than inulin.The viscosity of SASDF was lower than that of the reference substance pectin at the same mass concentration.At the mass concentrations of 1%,5%and 10%,the SASDF solution behaves as a non-Newtonian fluid.The viscosity of SASDF solution increases with the increase of concentration and decreases with the increase of temperature.,The viscosity of 5%SASDF solution increases with the increase of pH value in the range of pH 13,and decreases with the increase in the range of pH 36.The viscosity of 5%SASDF solution was almost unaffected by NaCl addition,but the addition of CaCl2 had a significant impact on its viscosity,which may be due to the cross-linking of calcium ions and SASDF.SASDF had significant effects on the effective particle size,particle size distribution,Zeta potential,apparent shear viscosity and microstructure of protein-encapsulated nano-emulsion before and after digestion,and showed a concentration-dependent manner.The digestion curves of nanometer emulsions showed a second order pseudo first order reaction whether SASDF were present or not.The reaction rate constant k1 in the rapid reaction stage decreased with the increase of SASDF concentration,but in the slow reaction stage,the reaction rate constant k2 showed no correlation with the concentration.However,the final digestibility of fat in the nanometer emulsion decreased with the increase of SASDF in the system. |
