Effect Of High Pressure Microfluidization On Crystal Structure And Properties Of Sweet Potato Starch And Potato Starch

High pressure microfluidization（HPM）is a new type of green and environmentally friendly starch modification treatment technology.This study used sweet potato starch and potato starch as raw materials,and used the mechanism of mechanochemistry to study effect of HPM on the crystal structure of potato starch and sweet potato starch.The potato starch and sweet potato starch were treated once under different HPM treatment pressures,and the sweet potato starch was treated for different times under the condition of 40 MPa.X-ray diffraction（XRD）,laser confocal microscope（CLSM）,scanning electron microscope（SEM）,polarizing microscope（PLM）,fourier transform infrared spectrometer（FTIR）,differential scanning calorimeter（DSC）,low-field nuclear magnetic resonance tester（LF-NMR）,thermogravimetric analyzer（TGA）,rheometer（Rheometer）,and other methods were used to study effects of different HPM treatment pressures and treatment times on the crystal structure and properties of sweet potato starch and potato starch.And the related theories of mechanochemistry were used to study the influence mechanism of HPM.The main research results were as follows:（1）Effects of different high pressure microfluidized treatment pressures on crystal structure and properties of potato starch.After 40 MPa treatment,there were scratches and other destructive traces on the surface of potato starch granules,the crystallinity of starch granules and the intensity of infrared and Raman diffraction peaks decreased,while the degree of gelatinization increased,and the thermal stability decreased.The viscoelasticity,shear recovery ability,and freeze-thaw stability of the gel also decreased（stressed stress）.After 80 MPa treatment,recrystallization occured in the starch granules,the crystallinity increased,the internal structure became dense,the degree of ordering and thermal stability increased.The strength of the gel,shear recovery ability,etc.were improved（aggregation stage）.The HPM 120-160 MPa treatment damaged severely the potato starch granule morphology,the crystal structure,ordered structure,the starch gelatinization degree increased sharply,and the gel system was more susceptible to shear and frequency of the rheometer（agglomeration stage）.（2）Effects of different high pressure microfluidized treatment pressures on crystal structure and properties of sweet potato starch.After sweet potato starch was treated with a lower HPM treatment pressure（40 MPa）,its starch granule crystallinity,gelatinization enthalpy and R_1024/995decreased,thermal stability weakened,static rheological behavior and dynamic rheological behavior of the gel and the freeze-thaw behavior were affected to a certain extent,which corresponds to the mechanochemical stress stage.However,when the treatment pressure increased to 80 MPa,the inside of the starch became compact,the particle size decreased,the double helix structure was better,the free water penetration was weakened,and the disintegration resistance of the gel was improved.As the treatment pressure increased,the shearing force generated by the HPM would destroy the hierarchical structure of the starch granules,and the amylose would partially dissolve and produce agglomeration effect,resulting in enhancing rheology of the starch gel.The penetration of water molecules increased,the gel produced a rough sponge structure after freeze-thawing,and the water separation rate increased.（3）Effects of different times of high pressure microfluidization on crystal structure and properties of sweet potato starch.Compared with pressure treatment,effect of treatment times on sweet potato starch was more obvious,and the granular structure was damaged more obviously.Three times of sweet potato starch was in the transitional stage between the stress stage and the aggregation stage.The structure of starch granules was damaged,but the crystallinity and degree of order showed an upward trend,and the surface of the granules was not obvious.After 5 times of HPM treatment,the starch was in the aggregation stage,the molecules inside the starch granule were rearranged,the infrared and Raman absorption peaks and the gelatinization enthalpy increased,and the thermal stability was improved.The network within the gel have better crosslinking properties,and the gel strength and freeze-thaw stability were improved.After HPM 7-9 times treatment,gelatinization degree of the starch increased,many damaged particles agglomerated together,the particle size increased.The crystallinity and gelatinization enthalpy significantly reduced,the amylose content increased,and the starch molecules became disordered seriously.The network entanglement of the gel became less,and the gel structure was rough.It could be seen that the high pressure,shearing force,cavitation and vibration generated by the HPM led to the physical damage of the starch granules,the destruction of the crystal structure,and the dissociation of the ordered structure and molecular structure.HPM had a significant mechanochemical effect on starch granules.This research broadened the research of mechanochemistry in the field of starch modification.