Effects Of Radio Frequency/Microwave Annealing Treatment On The Structural And Physicochemical Properties Of Potato Starch

Potato staple foodization is a national strategy.Potato with high starch content is a high-quality starch resource.Potato starch is which is high in viscosity and good in transparency.However,in practical industrial applications,starch is also limited by its own conditions?weak gel strength,low gelatinization temperature?,which needs to be modified for the practical application of the food industry.Traditional physical modification methods such as annealing treatment and heat moisture treatment modified starch by heat conduction,which often requires a lot of time and energy.Different from the traditional heating method,the radio frequency/microwave heating of the substance is completed by molecular friction and metal ion conduction,which have the advantages of uniform heat distribution,fast heating speed and low energy consumption.In this study,potato starch was annealing by microwave and radio frequency.The effects of moisture content and treatment time on the structure and physicochemical properties of potato starch were discussed and the mechanism was discussed.The main results are as follows:?1?After radio frequency annealing treatment,the granules affected rare flaws/fractures were observed on the surface,and even the melting and cracking of some small particles,could be clearly observed by a scanning electron microscope?SEM?.Partially missing and deformed also appeared in the polarized cross.The increased of water content had a protective effect on starch granules,and the damage of starch morphological structure gradually decreased with the increasing water content.However,longer processing time will cause more serious damage to the starch structure.The crystal form of potato starch with different water content changed from B to C type after radio frequency annealing treatment without concern the processing time.The crystallinity of starch increased with the water content increasing and decreased with the treatment time increasing.Radio frequency annealing treatment does not create new chemical groups in the starch,but changes the peak width and intensity of the infrared absorption peak.The volume average particle size(d_?4,3?)and surface area average particle size(d_?3,2?)of starch decreased with increasing water content and increasing significantly with the prolongation of treatment time.The changes in amylose and resistant starch?RS?content are consistent with crystallinity.Structural changes lead to physical and chemical properties change.The iodine blue value,iodine-binding capacity,water holding capacity,peak viscosity?PV?,breakdown value?BV?,transparency,solubility,swelling power,termination temperature?T_c?,enthalpy value??H?and consistency coefficient of starch increased with the water content increasing,but the trough viscosity?TV?,final viscosity?FV?,setback value?SB?,storage modulus?G??,loss modulus?G??and flow characteristic index gradually decreased as the water content increasing.Longer treatment time will increased the iodine blue value,water holding capacity,TV,FV,SB,G?,G?and consistency coefficient of starch.PV,BV,transparency,solubility,swelling power,T_c,?H and flow characteristic index decreased with increased processing time,and the treatment time had no effect on iodine-binding capacity and gelatinization temperature.?2?The regularity of starch morphology,molecular structure,amylose content,resistant starch content,viscosity,transparency,solubility,swelling power,G?,G?,consistency coefficient and flow characteristic index after microwave annealing treatment is consistent with the radio frequency annealing treatment while the different water content and microwave treatment time have no effect on the crystal form and particle size distribution of potato starch.The effect of water content on the iodine-binding capacity of starch was not significant,and the treatment time increased the iodine-binding capacity of starch,but decreased the water holding capacity of starch.When the starch has the same water content,the iodine blue value,water holding capacity,PV,BV,transparency,solubility and swelling power of the radio frequency annealing starch sample are higher than those of the microwave annealing starch,while the crystallinity,d_?4,3?,d_?3,2?,amylose content,RS content,iodine-binding capacity,TV,FV and SB of the microwave annealing starch are higher than those of the radio frequency annealing treatment.When starch is treated at the same time,d_?4,3?,d_?3,2?,amylose content,iodine blue value,water holding capacity,TV and FV of the radio frequency annealing starch samples were higher than those of microwave annealing treatment,while the microwave annealed starch samples had higher crystallinity,RS content,PV and BV than the radio frequency annealed starch samples.In summary,the effect of radio frequency/microwave on the physical and chemical properties of starch is similar to that of traditional annealing treatment,the advantages are fast processing,short time-consuming and low energy consumption.After radio frequency/microwave annealing treatment,the transparency,?H and water holding capacity of starch were greatly affected.The crystallinity and viscosity properties of starch after radio frequency/microwave annealing treatment were quite different.