Study On The Extraction And Structural Properties Of Starch Blocklets From Waxy Rice

In this paper,addresses the problems of the structure of the basic constituent units of natural starch granules and their structural relationship with amylopectin and other molecules,as well as the heterogeneity and structural uncertainty of starch nanomaterials.The methods of freeze-thaw treatment combined with low temperature acid hydrolysis,ultrasonic crushing and the physical properties of the products were studied.The topic is novel that has certain theoretical value and application prospects.Using waxy rice starch as material,starch blocklets were extracted by freeze-thaw treatment low temperature acid hydrolysis and freeze-thaw treatment ultrasonic breaking method.The research focus was to reduce the damage of blocklets in the extraction process and improve the extraction efficiency.At the same time,the physical properties of the blocklets were analyzed by scanning electron microscopy(SEM),differential scanning calorimeter(DSC)and X-ray diffraction.The results show that freeze-thaw treatment and low-temperature acid hydrolysis is a low loss and high-efficiency extraction method.Although the extraction efficiency of freeze-thaw treatment ultrasonic crushing method is significantly improved,but the crystal structure of blocklets is damaged by ultrasonic.Therefore,this method can be used as the preparation method of nanomaterials,but it is not suitable for the extraction of non damaged blocklets.The specific research contents and main conclusions are as follows:(1)The method of freeze-thaw treatment combined with low temperature acid hydrolysis was used to extract the blocklets glutinous rice starch to improve the yield and reduce the damage of blocklets starch.It was found that the crystal swelling pressure produced by freeze-thaw treatment could effectively loosen the structure of starch granules.The effects of freeze-thaw treatment times on the yield and damage degree of blocklets particles were studied.It was found that with the increase of freeze-thaw times,the free rate of blocklets particles increased during acid hydrolysis at low temperature.The yield of blocklets in unit time was significantly improved,and only three times of freeze-thaw treatment was more than three times higher than that without treatment.By scanning electron microscopy(SEM),it was found that the morphology of the blocklets extracted by freeze-thaw treatment and acid hydrolysis without treatment was more complete,and the particle size distribution curve was closer to the reality of the real blocklets.(2)It was found that the efficiency of freeze-thaw treatment ultrasonic crushing was 26 times higher than that of freeze-thaw treatment acid hydrolysis.Under the condition of ice bath,25% of the starch suspension was treated by freeze-thaw,and450 W,20 k Hz,50% of the output power was ultrasonic crushing for 90 min.Through SEM observation,it is found that the blocklets particles are elliptical or spherical,with complete blocklets morphology characteristics.The average particle size is 27 nm,slightly higher than the average particle size of acid hydrolysis(22 nm),which is greatly affected by ultrasonic treatment power and concentration of starch suspension,while less affected by ultrasonic treatment time.(3)Through the analysis of X-ray diffraction(XRD)and differential scanning calorimeter(DSC),it was found that the damage degree of blocklets particles extracted by freeze-thaw treatment low-temperature acid hydrolysis method was significantly reduced,and the crystal structure was almost not affected by acid hydrolysis;however,the crystal structure of blocklets particles extracted by freeze-thaw treatment ultrasonic crushing was completely destroyed,and the relative crystallinity was about 10%,which was higher than that of original starch(42.01%)The results of XRD showed that there was only one weak crystal peak or no obvious crystal peak,almost all of them showed dispersion characteristics;FTIR analysis showed that: Although the positions of the characteristic peaks corresponding to the original starch were not changed,the strength of the characteristic peaks were weakened.In addition,the aqueous solutions of the nanoparticles extracted by the two methods showed high stability.