Study On The Synthesis, Characterization And Properties Of Acetylated Corn Starch

The range of application of native starch is restricted seriously because of the updated technology, process and equipment. To improve the performance of native starch and expand the range of application, the defects of intrinsic properties of native starch could be perfected by the different methods of modification, which is a significant research topic. In addition, modification can afford the new speciality or functionality to the native starch to satisfying the industrial requirements.In this thesis, the synthesis, characterization and functional properties of acetylated corn starch (ACS) were carried out. The high, medium, low substituted ACS was synthesized by native corn starch (NCS) with acetic anhydride. The factors that could affect the degree of substitution (DS) were discussed systematically. According to these results, the reaction conditions were optimized. Besides, the functional properties of low substituted ACS as food thickener were studied. Finally, the factors that could affect the diameters and encapsulation efficiency (EE) of drug-loaded ACS nanoparticles were investigated and the drug release of the drug-loaded starch-based nanoparticles was studied. The main results were summarized as below:1. The optimized reaction conditions of synthesizing the low substituted ACS in the water with sodium hydroxide (NaOH) as a catalyst are:reaction temperature,30℃; reaction time,150min; pH,8.2; the ratio of the volume of the water to the weight of the NCS (VH2O/mNCS),1.0625; the weight ratio of the acetic anhydride (AA) to the NCS (mAA/mNCS),0.0625. According to these reaction conditions, the optimal DS of0.07and reaction efficiency (RE) of67.05%of the low substituted ACS were obtained. The optimized reaction conditions of synthesizing the medium substituted ACS in the acetic acid with the sulfuric acid as a catalyst are:reaction temperature,75℃; reaction time,150min; the volume of the sulfuric acid (Vsulfturic acid),2.5mL; the volume ratio of the AA to the acetic acid (VAA/Vacetic acid),1:1. According to these reaction conditions, the optimal DS of1.85of medium substituted ACS was obtained. The optimized reaction conditions of synthesizing the high substituted ACS in the acetic acid with the p-toluenesulfonic acid (PTSA) as a catalyst are:reaction temperature,70℃; reaction time,150min; the weight of PTSA (mPTSA),0.3g; the VAA/Vacetic acid,1:1.According to these reaction conditions, the optimal DS of2.85of high substituted ACS was obtained. The structure of ACS was characterized by Fourier Transform Infrared Spectroscope (FTIR), X-Ray Diffractometer (XRD), Differential Scanning Calorimeter (DSC) and Scanning electron microscope (SEM). The results showed that the high, medium and low substituted ACS can be synthesized by the NCS with AA in different reaction conditions.2. The low substituted ACS and NCS were heated to forming the starch gels. The solubility, swelling power, clarity, freeze-thaw stability, retrogradation and the stability of the viscosity that could be affected by DS were discussed. The results showed that the low substituted ACS can be used as the food thickener in the food industry.3. The drug loaded ACS nanoparticles were synthesized by the nanoprecipitation with the ACS with three different DS1.85,2.64and2.85. The structure of the drug loaded ACS nanoparticles was characterized by FTIR, XRD and SEM. The factors which include the DS, the weight ratio of the ACS to the ibuprofen (mACS/mIBu) and the volume ratio of the water to the acetone (VH2O/Vacetone) could affect the EE, diameters and drug release of the drug-loaded ACS nanoparticles were investigated. The results showed that the medium and high substituted ACS can be used for the encapsulation of the hydrophobic drugs (IBU) and potentially applied in the pharmaceutical industry.