Study On The Granule Property And Gelatification Of Chinese Water Chestnut

Chinese water chestnut is an abundant and special resource in china, and Chinese water chestnut starch (CWCS) has good gelling character and functional property, which exceeds many other starches. Comparing to corn starch and cassava starch, exploitation and reports on CWCS is so poor in China, although China is one of the original places of water chestnut. Modern methods and theory of polymer science were used to investigate and illuminate CWCS gel. Granular structure, gelatinization, retrogradation with different water content and digestibility related to gelatinization were also studied. The thesis affords experimental and theoretical evidences on CWCS for understanding and utilizing the starch, so it is of great importance. The main results are as follows:CWCS was extracted by water. The purity of CWCS was identified to be high with correlative analysis. The content of amylose in CWCS is 27.3% by colorimetry. Scanning electron micrographs (SEM) show that the CWCS granules are oval or multangular with the average size about 8μm, the surface of which are smooth and level off. The size of CWCS granule determined by laser diffraction analysis is consistent with that of SEM. X-Ray diffraction pattern suggests that CWCS is C-type and similar to A-type. The degree of crystal is 25.57%.Compared to cassava starch and corn starch, CWCS has the smallest gelatinization enthalpy, highest viscosity and best freeze-thaw resistance. The swelling power and solubility, transparency and sedimentate property are between cassava starch and corn starch. Gelatinized and retrograde CWCS have great difference in in vitro digestibility. The hydrolysis rate of retrograd CWCS is one third of that of gelatinized CWCS.To study CWCS gel, dynamic rheometer, texture profile analysis, SEM and X-ray diffraction were used, and the results are as follows:CWCS gel is a good elastomer with high viscosity. 8% concentration is the critical point of gel net formation. Temperature has more effect on the high concentration CWCS gel. The influence of temperature is obvious above 50℃, but there is slight effect when it is below 50℃. For texture testing, the CWCS concentration, gelling temperature, the amount of sodium chloride, sucrose, glycerol monostearate, citric acid have different influences on the gel hardness, springiness, cohesiveness and gumminess. There is much difference between the freeze-thaw CWCS gel and normal CWCS gel, but little difference among the CWCS gel with different freeze-thaw times. The CWCS gel changed from irregular to ordered shape with regular holes after freeze-thaw. The gelatinized CWCS could form new crystal structure when it retrograded at room temperature and under freezing-thawing, but no much difference. Cassava starch and corn starch have the same results.