| The degree of substitution of the esterified starch prepared by the traditional process is lower.Microwave method was introduced into the chemical modification process of starch to improve the degree of chemical reaction and obtain starch with high degree of substitution.Wheat starch and potato starch were used as raw materials,and the starch was treated with600 W microwave.And the esterification reaction of microwave starch or raw starch of potato and wheat was carried out respectively with acetic anhydride and glacial acetic acid(1: 1)as esterifying agent to obtain the corresponding esterified starch.And the structure and physical and chemical aspects of the system analysis of modified starch and the nature of the original starch.The main results are as follows:(1)After the wheat starch was treated by microwave,the starch granules expand and the volume increases.The surface of the granules become rough,and the surface of the starch appeares sag,small holes and fine cracks,but the starch shape does not change.But potato starch granules ruptures,the surface of the particles appeares depression and pores and starch shape changes,being amorphous shape.The polarized crosses of the ruptured starch are distorted or disappear.But the polarized cross of the broken potato starch is distorted or disappears.The crystallinity of wheat starch is reduced,but the crystal form does not change,and it is still type A.The crystallinity of potato starch increases,and the crystal structure changes,from the original B-type structure into C-type structure.The solubility and swelling of microwave starch at 50 ℃ are higher than that of the original starch.However after 60 ℃,the starch begin to gelatinize,the solubility and swelling degree of starch increase,but lower than that of the original starch.The solubility of microwave potato starch is higher than that of the original starch at 50 ℃ and 90 ℃,which is lower than that of the original starch at60-80 ℃,and the swelling degree is higher than that of the original starch at 50 ℃,but lower than that of the original starch at 60-90 ℃.After microwave treatment,the final viscosity and setback of wheat starch decrease,while the setback and final viscosity of potato starchdecrease.Microwave irradiation reduce the transparency,peak viscosity,minimum viscosity,breakdown and enthalpy of wheat and potato starch,but the gelatinization temperature increased.(2)The degree of substitution of potato starch and wheat starch increased with the increase of esterifying agent,and the degree of substitution and acetyl content of starch after microwave treatment were higher than that of original starch.After the esterification of the original starch,some small depressions occurred on the starch surface,the polarized cross of the starch was distorted,the cross center area was missing,the starch grain boundaries became blurred;and the microwave starch was aggregated into irregular large particles;The polarized cross becomes blurred,and the polarized cross of the aggregated particles disappears.The crystallinity of esterified starch and microwave esterified starch is decreasing,but the crystal structure has not changed.The solubility,swelling and transparency of the esterified starch of wheat increased with the increase of the esterifying agent.The solubility of the original potato esterified starch increase at 50-70 ℃,decrease at 80 ℃,while the microwave esterified starch gradually increase.After the esterification of wheat starch,the gelatinization temperature and enthalpy of starch decreased,while the gelatinization temperature of microwave esterified starch was also decreased,but the enthalpy was basically unchanged.The microwave esterification of potato Gelatinization temperature is basically unchanged,the thermal enthalpy is basically increased.(3)When the addition amount of the esterifying agent is 12%,the degree of substitution of microwave starch is the largest,and it is added to wheat and the potato starch.The hardness,elasticity and cohesion of the starch gel are reduced. |
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