Effect Of High Pressure Homogenization On Starch Structure,Properties And Its Mechanochemical Effect

In this research,corn starch and mung bean starch were used as raw materials,and they were processed under 100 MPa 1,3,5,7 times,respectively.In addition,corn starch was processed at the homogenizing pressures of 20,60,100 and 140 MPa successively to analyze the changes of microstructure and physicochemical properties.The mechanochemical effect of high pressure homogenization on starch were revealed.In this study,the structure and physicochemical properties of starch modified by different homogenizing conditions were analyzed by scanning electron microscope(SEM),confocal laser scanning microscopy(CLSM),polarizing microscope(PLM),X-ray diffraction(XRD),rapid visco analyzer(RVA)and differential scanning calorimetry(DSC),etc.And the relationships and mechanisms between structure and properties were revealed.The results showed that:(1)The microstructure of starch modified by different homogenizing times under 100 MPa were destroyed.and physicochemical properties of starch had changed significantly.Compared with mung bean starch(C type pattern),the common corn starch(A type pattern)was more likely to be destroyed and the mechanochemical effect of physical modification were more obvious.Corn starch was loading stage at the homogenizing times of 1 under 100 MPa,The sub-crystalline regions and crystalline regions of starch granule were destroyed when the homogenizing times was 3 to 5.In addition,There were spherical structure and corn starch entered into the aggregation stage.The channel structure and spherical structure showed a significant decreasing and corn starch entered into the agglomeration stage at the 7times of high pressure homogenizing treatment.Whereas,the amorphous of the mung bean starch was destructed at 1 to 3 times of homogenizing treatment,the degree of expansion and gelatinization temperature were decreased at 5 times of homogenizing treatment.Besides,the amorphous of the mung bean starch granule was damaged seriously and starch granules began to accumulate.At the 7 times of high pressure homogenizing,the gelatinization temperature and weight loss rate increased obviously,Whereas,the transmittance and maximum weight loss temperature showed a significant decreasing,the crystal structure was destroyed significantly and agglomeration effects occurred in starch granules.(2)Different homogenizing pressures had different mechanochemical effect on the amorphous,sub-crystalline regions and crystalline regions of corn starch granule,and typical aggregation and agglomeration effects occurred successively in starch granules.There were spherical structure with the increase of pressure from 20 to 100 MPa,and this phenomenonwas most obvious at the pressure of 100 MPa.In addition,the starch granules began to accumulate at this stage.When the homogenizing pressure was 140 MPa,the channel structure and spherical structure showed a significant decreasing.At the same times,polarization cross was damaged and corn starch entered the agglomeration stage.Compared with corn starch modified by different homogenizing times under 100 MPa,the granule structure and properties had changed weakly.Therefore,the effects of physical modification were more obvious by improving the homogeneous times at the pressure of 100 MPa.(3)High pressure homogenization pretreatmen destroyed crystal structure of cationic starch and improved the chemical reaction activity of starch.And this phenomenon was the most pronounced at the stage of aggregation.At this stage,the peak viscosity,transmittance and chemical reaction activity of cationic starch were also highest.In addition,the degree of substitution(DS)and reaction efficiency(RE)increased by 43.80% and 43.86%,respectively.Therefore,the starch of aggregation stage will be the best choose to prepare the cationic starch.