| Starch is an important industrial material. Thermal treatment will have effects on physical property of starches. The mechanism and application of thermal treatment on starch physical property and enzyme resistance is studied in this dissertation.1. The transparency, digestibility and freeze-thaw stability of starches have decreased after HMT Due to the formation of resistant starch. There are some differences among them. The swelling power and solubility showed an increase after autoclaving. But when the temperature goes high the increase becomes slow.2.There are some changes in starch granule appearance through HMT treatment. The granule appearance of maize starch and mung bean starch has undergone little transformation, but the granule of potato starch has changed a lot which shows some characteristics of non-crystal materials. These changes result in the low extraction rate of resistant starch. The SEM pictures of starches treated under excessive water show all the appearance properties of three starches have disappeared. The granule appearance differences of different starches can't be judged from SEM pictures. The X-Ray diffraction (XRD) plot of starches treated under excessive water shows that the crystallization has changed in varying extent. Disappear and emergence of some peaks is the results of the treatment. There is a strongest peak and a sub-strongest one at the position of 17(2θ ) and 14(2θ ) respectively. The intensity of peaks has increased compared with native starches. These all show the crystallization has rearrangement after autoclaving. The enzyme resistance of treated starches is due to the forming of new crystallization. The degree of crystallization is not proportional to the content of RS. The enthalpy of starches treated under excessive water decreases. When treated under excessive water the starch granule has undergone a gelatinization and retrogradation process which led to the collapse of starch granules. Short amylose chains of different starches have joint together to form crystalline which result in a high extraction rate of RS.3.Under balance moisture, the DSC plot shows that the peak shifts to high temperature and the enthalpy increases in the first place and then decreases. Starch treated in excessive water with a high content of RS has a high enthalpy value.4.Water content, temperature, autoclaving time, drying temperature and time, cooling and freezing time, etc. have effects on the extraction of resistant starch(RS) when starches treated in excessive water. The pH value has no effect on the extraction of RS. The optimum conditions and RS extraction rate of potato starch, maize starch, and mung bean starch concerning RS extraction are as follows: 70% water content, autoclaving temperature 140℃, autoclaving time 70min, and drying temperature 60 ℃ with 1.51% RS; 70% water content, autoclaving temperature 140℃, autoclaving time 70min, and drying temperature 60℃ with 4.83% RS; 70% water content, autoclavingtemperature 140 ℃, autoclaving time 50min, and drying temperature 70 ℃ with 5.83% RS.5.The rheologyical property of flours enriched with RS will be changed according to the amounts of adding. When the content of RS is below 10% the rheological property of flours shows little change. The quality of RS enriched staple foods should be improved. The effect of RS on the texture property of steamed bun produced in the north of China shows that RS has a marked influence on the hardness and springiness of steamed bun. The more of the RS, the worse of the texture property is. But RS has little influence on the specific volume of steamed bun. The edible property of RS enriched steamed bun will be improved with the join of quality improving agents. The optimum formula of quality improving agents has been developed.
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