Effect Of Rolling On Structures,properties Of Starch And Mechanism Of Assisted Preparing High Quality Acetylated Starch

In this study,sweet potato starch,cassava starch and pea starch were used as raw materials.X-ray diffraction（XRD）,confocal laser scanning microscope（CLSM）,scanning electronic microscope（SEM）,polarizing light microscope（PLM）,fourier transform infrared spectroscopy（FTIR）,laser confocal micro-Raman spectroscopy（LCM-Raman）,differential scanning calorimetry（DSC）,low-field nuclear magnetic resonance（LF-NMR）,thermogravimetry（TGA）,rheometer（Rheometer）,rapid visco analyzer（RVA）and other methods were used to study the effect of different rolling treatment time on the structures and physicochemical properties of native starch.And the acetylated starch with low degree of substitution was prepared to investigate the effect of rolling treatment on the quality of acetylated starch.The mechanism of rolling on the quality of acetylated starch was analyzed according to the related theories of mechanochemistry.The main results on the structures and physicochemical properties of native starch and the quality of acetylated starch were as follows:（1）Effects of rolling treatment on the structures,physicochemical properties of sweet potato starch and the quality of acetylated sweet potato starch.After 2 h of rolling treatment,compared with unrolling treatment starch,the crystallinity reduced and the diffraction peak at17.8^°level disappeared,the T₂value and storage modulus increased,gelatinization enthalpy and apparent viscosity decreased,and thermal stability weakened（stress stage）.After 5 h of rolling treatment,the apparent viscosity was declined,while the thermal stability of starch grew.Compared with that of 2 h of rolling treatment,the crystallinity increased,starch molecular in crystalline region was highly ordered,value of T_2,2disappeared（aggregation stage）.After 7-18 h of rolling treatment,the crystallinity,gelatinization enthalpy,apparent viscosity and thermal stability significantly declined,while the value of T_2,1increased,the bulges and holes appeared on fracture surface of some starch granules（agglomeration stage）.After 2 h and 7 h of rolling treatment,the reaction efficiency increased to 74.45%and 75.40%respectively,and other qualities（solubility,swelling power and peak viscosity）of acetylated sweet potato starch increased prominently.However,the quality（solubility,swelling power and peak viscosity）of acetylated sweet potato starch after 5 h of rolling was very poor.（2）Effects of rolling treatment on the structures,physicochemical properties of cassava starch and the quality of acetylated cassava starch.After 2 h of rolling treatment,the cracks appeared in the central cavities,crystallinity,gelatinization enthalpy and apparent viscosity decreased,T₂value and particle size increased,and thermal stability weakened（stress stage）.After 8 h of rolling treatment,crystallinity,gelatinization enthalpy and apparent viscosity increased,the starch molecular in crystalline region was more ordered,while storage modulus decreased,value of T_2,2disappeared（aggregation stage）.After 12-18 h of rolling treatment,the crystallinity,gelatinization enthalpy,apparent viscosity and thermal stability significantly decreased,T_2,1values and particle size increased,a large number of small particles were attached to large particles,the appearance of starch granules was seriously damaged（agglomeration stage）.After 2 h and 12 h of rolling treatment,the reaction efficiency of the acetylated cassava starch increased by 71.61%and 72.77%respectively,and other qualities（solubility,swelling power and peak viscosity）were significantly improved.However,the quality of acetylated cassava starch after 8 h of rolling was very poor.（3）Effects of rolling treatment on the structures,physicochemical properties of pea starch and the quality of acetylated pea starch.After 2 h of rolling treatment,particle size increased,crystallinity,gelatinization enthalpy and apparent viscosity decreased,the small water peak with large fluidity appeared in the graph of transverse relaxation time（T₂）and the thermal decomposition rate increased（stress stage）.After 6 h of rolling treatment,crystallinity and gelatinization enthalpy increased,storage modulus,particle size and apparent viscosity decreased,T_2,2values disappeared（aggregation stage）.After 8-18 h of rolling treatment,the crystallinity,apparent viscosity and thermal stability significantly decreased,while value of T_2,1increased,starch granules were seriously deformed,growth rings,central cavities and elongated hilum regions were blurred and even disappeared（agglomeration stage）.After 2 h and 8 h of rolling treatment,the reaction efficiency increased to 76.56%and73.09%respectively,and other qualities（solubility and swelling power）of acetylated pea starch increased prominently.However,the quality（solubility and swelling power）of acetylated pea starch after 6 h of rolling was very poor.Therefore,Rolling treatment could produce significant mechanochemical effect on starch granules,improve the chemical activity of starch,and then improve the quality of acetylated starch.This study provides a simple and effective method for the preparation of high quality acetylated starch,and lays a theoretical foundation for the future study of advanced equipmen for the preparation of high quality modified starch.