Preparation And Properties Of Rice Cationic Starch With Pulsed Electric Field

In the rice production process,a large amount of broken rice is produced for various reasons,but its chemical composition(especially starch and protein)is almost the same as that of intact rice.The utilization of efficiency broken rice is extremely low,resulting in waste of resources.With the development of science and technology,people pay more and more attention to the utilization of resources,and this promote the application of rice starch.In addition,the reprocessing and utilization of stockpiles for the storage period is also a big problem that needs to be solved urgently.Natural rice starch is insoluble in cold water,and the physical and chemical properties of starch paste are also insufficient,which limits its industrial application.The research on the modification of rice starch has given it unique functions and characteristics and expanded the application range of rice starch,which is also a research hotspot in various starch fields in recent years.In this paper,rice starch was used as raw material to prepare low-substituted cationic starch by wet electric method after treating rice starch by pulse electric field,and the physicochemical properties and reaction mechanism of the sample were analyzed.The pulsed electric field was used to pretreat rice starch,and the effects of pulsed electric field on the structural characteristics and physicochemical properties of starch granules were studied from two aspects:different electric field strengths and different effective treatment times.Scanning electron microscopy(SEM)revealed that the surface of the starch particles was damaged by the electric field.Infrared(FTIR)characterization and X-ray diffraction(XRD)characterization results indicate that pulsed electric field treatment of rice starch does not introduce new functional groups,nor does it alter the crystalline structure of starch,and is a physical modification treatment.After the pulsed electric field treatment,the transparency of the rice starch paste was increased from 6.2%to 32.4%,the precipitation rate decreased from 58.31%to 22.53%,and the retrogradation and freeze-thaw stability were improved.Wet-processed cationic starch with low degree of substitution was prepared and the samples were characterized and analyzed for physicochemical properties.The results show that the pulsed electric field treatment can increase the degree of substitution of cationic starch.When the pulsed electric field intensity is 6 kV/cm and the treatment time is 1200 μs,the degree of substitution of cationic starch increases from 0.0219 to 0.0246.The structure of the prepared cationic starch samples was characterized by SEM.It can be seen that the higher the electric field intensity,the greater the degree of substitution and the larger the particle aggregation;the infrared spectrum results show that the cationic starches are at 575 cm-1 and 1082 cm-1.The characteristic peaks of starch at 1156 cm-1 appeared at 1494 cm-1,indicating that the starch had been modified by etherification.X-ray diffraction analysis showed that the starch retained its original crystal after cationization.The characteristic peaks of the structure indicate the starch cationization process.The pulsed electric field does not introduce new characteristic peaks.At the same time,it also shows that the cationic starch with low degree of substitution is prepared and the reaction mainly occurs in the amorphous region.The influence of pulsed electric field treatment on the apparent activation energy of the etherification reaction was studied.The substitution degree of the cationic starch was used as an indicator and was obtained at different temperatures and different reaction times,the apparent activation energy of the chemical reaction was then calculated based on the kinetic equation of the etherification reaction.The results show that the etherification reaction conforms to the reaction mechanism of the secondary reaction kinetics.After 1200μs treatment at 6kV/cm,the cationization reaction was carried out.The apparent activation energy decreased from 50.216 kJ/mol to 37.579 kJ/mol,which was a decrease of 12.637 kJ/mol.