| The castanea mollissima blume was used to analyze its carbohydrates and digestionresistan features with chemical method and instrument HPLC. It also studied the extracting technology of chestnut starch and determined its content of amylose, amylopectin and the main chemicals. Finally, it discussed the physical and chemical properties of chestnut starch and the preparation technology of its resistant starch and the construction features of the resistant starch with instrument DSC, FT-IR, XRD. The following are the main conclusion:1. The chestnut contains 35.77% total starch, including 30.16% amylose, 69.84% amylopectin, 8.66% total soluble sugar, 3.97% reducing sugar, the rhamnose and the raffinose. The fresh chestnut contains 27.44% resistant starch, accounting for 68.93% of the total starch. Stored 24 hours, the cooked chestnut contains 5.46% resistant starch, accounting for 13.36% of the total starch. The chestnut has a high content of raffinose and resistant starch, which cause the chestnut being indigestible and developing its physiological function.2. The technology of extracting starch and removing protein for chestnut is:①chestnut kernel crushing;②b eating;③f iltering with a sieve;④g etting starch;⑤a djusting pH value to 8;⑥depositing on standing;⑦e xhaling the upper mixture;⑧repeating the step⑤to⑦;⑨d rying at 60℃;⑩getting chestnut starch. With this method, we can get the pure and coloury starch relatively. The starch granules of chestnut takes on obround, round and polygon and its diameter is 1.08-9.22um, the maximum length is 16.96um and its amylose content is 30.16%, amylopectin content is 69.84%. The starch paste of chestnut has strong degree of swelling and good freeze-thaw stability, but it has low transparency and its ageing resistance can't compare with potato starch.3. Through the method of hydrolyzing by pullulanase and the method of gelatinization and ratrogradation subsequently, it can get the high content resistant starch. The optimum condition of preparing resistant starch with pullulanase is: the concentration of starch slurry is 8%, pH value is 4.5, temperature is 50℃, dosage of enzyme is 40U, the time of enzymolysis is 10h, the time of gelatinization is 10min with 90℃and the time for cold storage is 24 hours. With this method, the resistant starch content can reach 30.34%. The optimum condition of preparing resistant starch by autoclaving method is: the concentration of starch slurry is 25%, the time for autoclaving treatment is 50min, the time for cold storage is 6 hours and the pH value is 6. With this method, the resistant starch content reaches 17.16%.4. The instrument analysis shows that the resistant starch does not come into being new group. Forming resistant starch is because of its physical modification, not the change of its chemical structure. Compare infrared atlas of resistant starch and amylose, it nearly has no differences at characteristic absorption peak of their functional group. X-ray Diffraction atlas shows that resistant starch has crystal, comparing with amylose, it shows obvious differences at peak position and peak value. So it explains that the molecular structure of primary starch has been reformed after disruption causing the change of the crystalline structure of resistant starch. The TG, DTG and DSC curve of chestnut starch and resistant starch shows that the temperature of intense decomposition for chestnut starch is 311.6℃, while the temperature of crystal melted for resistant starch is 304.9℃, which lower than chestnut starch. So this phenomena shows that it has different type of crystal between chestnut starch and resistant starch. The chestnut starch is stable below 240℃and it can not be disintegrated, while the resistant starch can keep the crystalline structure stable below 290℃.In a word, the chestnut starch is easy to become resistant starch, which cause the chestnut being indigestible and found a good way to make deep processing of chestnut starch. It provides the scientific reference frame for chestnut development and utilization.
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