Preparation And Properties Of Cross-linked / Ultrasonic Enzymatic Hydrolysis Starch

In this thesis, self-made native yam starch (NYS) was used as raw materials. Optimal condition was obtained by single factors and orthogonal test and the optimal conditions of extraction of enzymatic hydrolysis starch (EYS) were pH5.5, temperature 55 ?, enzyme dosage 4%, time 22h, and ratio of alpha amylase and glucoamylase 1:8. The hydrolysis rate was 68.78%, and the methylene blue adsorption rate was 87.56%under the provided condition. Chemically modified yam starches were include: 1)cross-linked starch (CS1-CS4) was prepared with 2%-8% three sodium phosphate; 2)cross-linked enzymatic hydrolysis starch (CES1-CES4) was cross-linked starch (CS1-CS4)modified with alpha amylase and glucoamylase ; 3) ultrasound starch (US1-US4) was prepared in water with sonicate at frequency of 25-80kHz; 4) ultrasound enzymatic hydrolysis starch (US1-US4) was ultrasound starch (US1-US4) modified with alpha amylase. The particle morphology, particle size distribution, gelatinization properties, and viscosity of starches were studied by using scanning electron microscope (SEM), particle size analyzer,Rapid Viscosity Analyzer (RVA),differential scanning calorimeter (DSC) and other technical means.In comparison with the native yam starch, the surface of enzymatic hydrolysis starches were appeared significant pore with rough surface. It was observed that the median diameter of the enzymatic hydrolysis starch by the laser particle size analyzer was 16.31?m, less than 22.79?m of raw starch, and the specific surface area was larger than that of the raw starch, which was consistent with the methylene blue adsorption rate and SEM.DSC and RVA showed paste enthalpy and viscosity of EYS were decreased compared with NYS. The crystalline types is still C-type, however, the relative crystallinity increased,indicating that the enzyme function mainly in the non-crystalline regions of the starch hydrolyzed starch. FTIR showed the intensity of characteristic absorption decreased after reaction, and the peak shape, in the 1150 cm-1 was C-O which was redshift from 1163cm-1 to 1158.74cm-1.Cross-linked starch granule appeared depression with smooth surface. The median diameter of starch basically remained unchanged with the volume fraction of STMP increase. Tp value of gelatinization temperature increased. However, the gelatinization parameters showed an inverse trend, and the viscosity (peak,breakdown and setback viscosity) was lower than NYS. It was discovered that both the maximum weight loss temperature and relative crystallinity of cross-linked starch decreased. The chemical bond P-O and P=O absorption peak were occered. Hydrolysis rate and adsorption rate increased obviously of enzymatic cross-linking starch.The adsorption rate of starch was not changed obviously while the rate of hydrolysis increased with the increased of ultrasonic frequency in ultrasound starch. The surface part of the starch granules became rough, where was occurred some small holes and grooves.The polarization property was not changed. The particle size was smaller while the specific surface area was larger slightly. The enthalpy of paste was decreased and the viscosity(peak, breakdown and setback viscosity) was lower and smaller. The maximum weight loss temperature increased, and the relative crystallinity increased. After the enzymatic hydrolysis of starch, the adsorption rate and hydrolysis rate of starch increased rapidly.Surface of the starch granules became coarser than NYS. The enthalpy and viscosity of the paste decreased. The relative crystallinity increased, but the crystalline type of ultrasound enzymatic hydrolysis starch was not changed.