Effects Of Rolling On Structure,Properties Of Starch And Its Mechanochemical Effect

In this paper,using corn starch,potato starch,mung bean starch as raw materials,effect of rolling time on surface morphology,particle size distribution,crystalline structure,pasting properties and thermal characteristics of starch were comparatively analyzed by instrumental analysis techniques,which included scanning electron microscope(SEM),polarizing microscope(PLM),confocal laser scanning microscopy(CLSM),X-ray diffraction(XRD),fourier transform infrared spectroscopy(FTIR),differential scanning calorimeter(DSC),rapid visco analyzer(RVA)and thermogravimetric analyzer(TGA).On the basis of the previous work,the starch of three different mechanical chemical stages were selected to prepare cationic starch by wet process.The structure and properties of cationic starch were characterized and the activate mechanism of rolling on corn starch was revealed.The main results were as follows:(1)Effects of rolling on the structure and properties of corn starch.The results showed that when rolling processed for 3~9 h,rolling treatment had merely impact on double helix structure of amorphous region of corn starch granule.The CLSM results indicated that the central cavity of granule became larger and the channel was blurred after rolling treatment.In addition,some bulbous protuberances were formed on the granule surface at rolling treatment9 h.At the same time,the water solution index,welling power,transparency,peak viscosity and enthalpy presented a significant decrease(aggregation stage).As the rolling processing time increased to 12 h and 24 h,bulbous protuberances of particle surface became less obvious and the number of channels was increased.Particle size of granules was found to increase but opposite trend was found in enthalpy.At this stage,rolling destroyed the crystalline area of corn starch granules in accompany with the double helical content decreasing(agglomeration stage).(2)Effects of rolling on the structure and properties of potato starch.The results showed that the crystal structure and double helix structure of potato starch were destroyed,so that the difference between the internal crystals increased.When rolling treatment for 3~6 h,some starch granules were broke down,the fluorescent brightness weakened around the hilum and hollow structure was formed in the center of granules(loading stage).With the increasing of processing time,some bulbous protuberances were developed on the granule surface and the spherical structure was formed in the surroundings of hilum.Meanwhile,there was asignificant decline in the welling power,enthalpy,peak viscosity and gelatinization temperature(aggregation stage).As the rolling processing time increased to 12 and 24 h,particles were severely damaged and some debris attached to large particles.The CLSM results showed that the fluorescent brightness of particles became weakened,some particles were even no fluorescence phenomenon,which further illustrate the dissolution of amylose(agglomeration stage).(3)Effects of rolling on the structure and properties of mung bean starch.The results showed that the amorphous and part of the crystalline regions of mung bean starch were destroyed by rolling treatment 3~6 h(loading stage).With the increasing of processing time,recrystallization was happened inside starch granules.At the same time,some bulbous protuberances had formed on the granule surface and amylose was aggregated in the hilum area.And welling power,transparency,peak viscosity exhibited a significant decrease.Furthermore,water solution index,enthalpy and gelatinization temperature of the mung bean starch were increased(aggregation stage).As the rolling processing time increased to 12 and24 h,crystal structure had been severely damaged.Meanwhile,the particle morphology of starch underwent serious change in accompany with water solution index and transparency was increased.But opposite trends were found in enthalpy and welling power(agglomeration stage).(4)Effects of rolling pretreatment on the chemical reaction activity of cationic starch.The result indicated that the crystal structure of cationic starch was destroyed by rolling,which is beneficial for etherifying agent to penetrate inside the starch granules,so the rolling mechanical force increased significantly chemical reaction activity of the starch,and the cationic starch after rolling pretreatment could be gelatinized at room temperature.Among them,effect of the agglomeration stage(rolling treatment 12 h)was the most significant,and crystallinity degree of the cationic starch prepared at this stage was also broken most seriously.In addition,the degree of substitution,the reaction efficiency,the viscosities and the transmittance of starch at this stage were the highest,and the chemical reaction activity of starch was also the highest.