Effect Of Ultrasound On Structures And Properties Of Starch And Mechanism Of Preparing Octenyl Succinic Anhydride Modified Starch

In this study,cassava starch and pea starch were used as raw materials.Cassava starch and pea starch were treated for 20 min under certain ultrasonic power respectively.Besides,cassava starch was treated for a certain time under 500 W ultrasonic power respectively.X-ray diffraction?XRD?,confocal laser scanning microscope?CLSM?,scanning electronic microscope?SEM?,polarizing light microscope?PLM?,Fourier transform infrared spectroscopy?FTIR?,Fourier transform Raman spectroscopy?FTIR-Raman?,differential scanning calorimetry?DSC?,low-field nuclear magnetic resonance?LF-NMR?,thermogravimetry?TGA?,ultraviolet visible spectrophotometry?U-VVis?,rheometer?Rheometer?,rapid visco analyzer?RVA?and other methods were used to study the effect of different ultrasonic treatment power and time on the structure and physicochemical properties of cassava starch and pea starch.And the mechanochemical effect of different ultrasonic treatment stages on starch granules were further explored by ultrasonic cavitation experiments.In addition,octenyl succinic anhydride modified starch with low degree of substitution was prepared under 0,100,300,400 and 600 W ultrasonic power conditions respectively.The effect of ultrasonic treatment on the quality of octenyl succinic anhydride modified starch was studied,and the mechanism of ultrasonic treatment on the quality of octenyl succinic anhydride modified starch was analyzed by mechanochemical theory.The main results were as follows:?1?The effect of different ultrasonic treatment power on the structure and properties of cassava starch.After ultrasonic treatment at 100 W,the crystallinity,thermal stability and the ratio of 1047 cm^-1/1022?cm^-1 of cassava starch decreased,the content of starch granules changed,and starch granules were easy to gelatinize?stress stage?.After 300 W ultrasonic treatment,some bulges formed on the surfaces,the ratio of A₆₈₀/A₅₄₅ decreased,the thermal stability,gelatinization enthalpy and the ratio of 1047 cm^-1/1022?cm^-1 increased?aggregation stage?.After ultrasonic treatment at 400-600 W,starch granules were seriously deformed and the adherent fragments increased,the crystallinity,thermal stability and the intensity of Raman spectrum peak decreased significantly.And the hysteresis area and the amylose content increased,and starch granules needed less energy to break the double helix structure?agglomerating stage?.?2?The effect of different ultrasonic treatment time on the structure and properties of cassava starch.After ultrasonic treatment for a short time,the crystallinity and thermal stability of cassava starch granules decreased,the hysteresis area and amylose content increased,the gelatinization enthalpy decreased.Starch granules began to enter the stress stage.After ultrasonic treatment for 8 min,T_2,2 disappeared,the internal structure of starch granules became orderly,the thermal stability and gelatinization enthalpy increased,and the internal aggregation of starch granules was spherical structure,which was consistent with the aggregation stage of mechanochemical effect.After ultrasonic treatment for 32-60 min,the crystallinity and thermal stability of starch granules decreased significantly,the content of amylose increased significantly,the damaged starch molecules arranged disorderly,the particle sizes increased,and the appearance of starch granules was seriously damaged.This stage was the agglomeration stage.?3?The effect of different ultrasonic treatment power on the structure and properties of pea starch.After ultrasonic treatment at 100 W,part of amorphous area and microcrystalline structure of pea starch granules were destroyed,the crystallinity and thermal stability decreased,pores and central cavities began to become blurred?stress stage?.After ultrasonic treatment at 250 W,the crystallinity increased,the thermal decomposition rate decreased,and the gelatinization needed more energy?aggregation stage?.When the ultrasonic treatment power increased to 400-550 W,the crystallinity,thermal stability and gelatinization enthalpy of starch granules decreased significantly,the amylose content increased,the intensity of Raman spectrum peak decreased,the hysteresis area and particle sizes increased,starch granules were seriously deformed and starch molecules were highly disordered?agglomeration stage?.?4?The effect of different ultrasonic treatment power and time on cavitation effect.With the increase of ultrasonic treatment power and time,the consumption of sodium thiosulfate increased,that was,the amount of iodine released in the potassium iodide solution increased,and the color of emulsion constantly deepened.This indicated that the ultrasonic cavitation yield increased with the increase of power and time,and the ultrasonic cavitation effect became violent.The damage degree of tin foil also showed that the larger the ultrasonic force was,the more serious the damage to tin foil was,the more and larger the holes were.That was to say,the larger the cavitation effect produced by ultrasound.?5?Preparation of octenyl succinic anhydride modified starch by ultrasonic-assisted treatment and its effect on quality.Ultrasonic treatment was beneficial to the homogeneous reaction of esterifying agent and starch molecules,and to the improvement of chemical activity of starch and the quality of octenyl succinic anhydride modified starch.The degree of substitution,reaction efficiency,solubility,swelling power,viscosity and the enzymatic resistance of octenyl succinic anhydride modified starch were significantly improved in the stress stage and agglomeration stage,the gelatinization temperature decreased significantly,and the chemical activity of starch granules was higher.Therefore,the quality of octenyl succinic anhydride modified starch prepared by ultrasonic-assisted treatment was improved in the two stages.While the quality of octenyl succinic anhydride modified starch decreased in the aggregation stage.