Research On Intermittent Microwave Drying Properties And The Process Optimization Of Water Chestnut Starch

As an important raw materials of food processing,water chestnut starch has great advantages in resources and development.At present most of water chestnut starch processing enterprises achieved heat by wood burning coal and air heating which were low efficiency,difficult health standards and affect the quality.Microwave heating has the unique characteristics such as short drying time,high efficiency energy saving,high product quality and so on,therefore water chestnut starch could dry through intermittent microwave drying.Drying characteristics,kinetics model,drying process and properties of Water Chestnut Starch were studied.Theoretical basis was provided basing on study of microwave drying starch,the traditional horseshoe starch industry technology progress were promoted and the quality of the products were improved.The main conclusions included the following aspects.(1)Wet starch intermittent microwave drying process showed the acceleration,constant speed and speed down the three stage.the higher microwave power is,the longer heating time is,the greater the drying rate is,the faster moisture content decrease,the shorter accelerating,constant speed and deceleration time is;the greater the amount of loading is,the longer the intermittent time is,the smaller the drying rate change.more slowly water content decrease,the longer the drying time is.By fitting the drying model of five kinds of classical analysis,Results showed that water chestnut wet starch intermittent microwave drying kinetics model satisfies the Page equation MR = e-ktn,,the predicted values agree well with the test results.(2)On the basis of' single factor experiment,the optimum conditions of microwave intermittent drying of water chestnut starch were determined by orthogonal test,microwave power is 210W,loading capacity is 1.47kg/m2,heating time is 14min,and intermittent time is 0.75min.(3)From the perspective of transverse relaxation time(T2)inversion spectrum of water chestnut starch water,results showed that water of the microwave dried samples before and after were the combined water,weak bound water and free water;After samples were dried by microwave in T21(0.12ms-1.52 ms),T21 peak signal amplitude was up to 98.8%,the combined water was the main.In T22(60007.62ms-10000.0ms),the amplitude of the signals were only the total signal 1.2%,ratio of weakly bound water and free water decreased significantly,some weakly bound water turned into bound water.(4)Microwave drying of Chinese water chestnut starch SEM photos showed that the particles were intact,smooth surface,large particles of the overall structure were the ellipsoid type,small spherical particle were analyzer;the particle size of D50= 8.51 ?m,D97= 22.95?m.The X-ray diffraction patterns showed that the starch structure was A type.DSC pattern showed thart the starch structure transition temperature To was 67.08?,the phase peak temperature Tp was 114.45??the endothermic peak was the melting peak of amylose and lipid double spiral crystal,the phase end temperature of Tc was 163.98??endothermic enthalpy ?H transformation is 385 J/g,the endothermic peak area was 111.945W/g.(5)Within 65-90?,solubility and swelling degree of microwave drying of water chestnut starch were increased with the increase of temperature and the transparent rate was 12.3%;Liquid volume percentage of water chestnut starch stabled in 62.2%,the viscosity was 98800 mPa·s,Viscosity fluctuation was 152.0%.Microwave water chestnut starch quality was better than starch of hot air drying.