Study On Preparation And Physicochemical Properties Of Sorghum Porous Starch Using Ultra-high Pressure Assisted Enzymatic Preparation

In this study,sorghum was used as raw material to extract sorghum starch.Firstly,compound saccharinized starch was used to study the preparation of sorghum porous starch,and the optimum process parameters for enzymatic hydrolysis were determined.On this basis,ultra-high pressure technology assisted enzymatic method was used to study the preparation of porous sorghum starch,which reduced the amount of enzyme added and the enzymolysis time.By measuring the starch oil absorption rate,water absorption,solubility and expansion,and specific volume,and using scanning electron microscopy,laser particle size analyzer,differential scanning calorimeter,rapid viscosity analyzer and other detection means,the analysis of the original starch and porous starch The differences in structure and physicochemical properties explored the effects of different pressure,holding time,and starch concentration on the structure and physicochemical properties of porous starch.The experimental findings are as follows:（1）The optimum technological parameters for enzymatic preparation of porous starch for sorghum are optimized by single-factor and orthogonal experiments:nzyme ratio 1:5,substrate concentration 25%,enzyme addition amount 3%,enzymolysis time 10h,enzymolysis temperature50°C and pH 4.6,the porous oil obtained under this process condition has the highest oil absorption rate of 132.04%compared with the native starch,it increased by 92.81%;Scanning electron microscopy results showed that the pore formation effect of high-cerium porous starch was better.（2）Compared with the native starch,porous starch obtained by enzymatic hydrolysis of porous starch and ultra-high pressure assisted enzyme significantly increased the oil absorption and water absorption.At the pressure of 300 MPa,pressure holding time of 20 min and a starch concentration of 1:1,the oil absorption and water absorption of the porous starch were as high as 132.04%and91.17%,respectively.The adsorption efficiency was equal to the oil absorption rate 132.04%and the water absorption rate 91.17%of conventional porous starch.These results can show that the ultra-high pressure assisted enzyme method reduces half the amount of enzyme added and 4 hours of enzymatic hydrolysis time compared with ordinary enzymatic hydrolysis.Changing the pressure,pressure holding time and concentration of starch solution all have a significant effect on the adsorption rate of porous starch.（3）The observation and analysis of starch samples by electron microscopy showed that the original granules of sorghum sorghum were complete,round,irregular and polygonal,and the surface was smooth;the sorghum porous starch granules prepared under the best enzymolysis process conditions remained intact.Filled with honeycomb holes,moderate pore size and depth.On the other hand,pores appeared on the surface of starch granules obtained by enzymolysis after ultra-high pressure treatment.Compared with enzymolyzed porous starch,porous starch granules remained intact,the pore size was larger,the pores were evenly distributed,the number of pores was larger,and the pore forming effect was better.Treatments with different pressures,starch concentration,and pressure holding time have an effect on the structure of the starch granules,which is consistent with the results of oil absorption and water absorption.（4）The results of solubility and swelling indicate that the solubility and swelling degree of porous starch obtained by common enzymatic hydrolysis and supercritical pressure assisted hydrolysis can achieve the same effect,both significantly higher than that of the original starch,with the increase of pressure holding time.The solubility and swelling degree of porous starch first increase and then decrease.As the pressure level increases,the solubility and swelling degree of porous starch first increase and then decrease.As the concentration of starch solution decreases,the solubility and swelling degree of porous starch gradually decrease.（5）The results of specific volume measurement showed that the specific volume of porous starch prepared by enzymatic hydrolysis and ultra-high pressure assisted enzymolysis can achieve the same effect,and both are significantly higher than the native starch.Different pressures,pressure holding times,and starch concentration treatment Porous starch has a certain effect on the specific volume.（6）The results of particle size analysis showed that the values of D_4.3,D_3.2 and D₅₀ of porous starch prepared by enzymolysis and ultra-high pressure assisted hydrolysis decreased compared with the native starch,and the specific surface area significantly increased,and the ultra-high pressure assisted enzymolysis preparation.The specific surface area of porous starch is significantly increased compared to enzymatically-decomposed porous starch.With the increase of pressure level,the specific surface area of porous starch first increased and then decreased.At a pressure of 300MPa,the specific surface area of porous starch was the largest;with the increase of pressure holding time,the specific surface area of porous starch increased first and then decreased.The specific surface area of porous starch was the highest when the pressing time was 20 min.With the decrease of the concentration of starch solution,the specific surface area of porous starch decreased gradually.When the concentration of starch solution was 1:1,the specific surface area of porous starch was the largest.（7）The results of DSC analysis showed that the thermal properties and the enthalpy of the porous starch were significantly higher than those of the native starch,while the values of T_o,T_p,and T_c of the porous starch prepared by the ultra-high pressure assisted hydrolysis were significant.It is higher than the native starch,but the enthalpy value decreases.Compared with the enzymolyzed porous starch,the porous starch prepared by the ultra-high pressure assisted enzyme method has a significantly lower enthalpy.When the pressure is high,the starch is over-pressed and the non-crystalline area is destroyed.During the enzymatic hydrolysis,the crystal structure of the small granular starch is destroyed,and the double helix structure is disintegrated,resulting in a decrease in the starch value.With the increase of pressure holding time,the starch and water molecules are subjected to pressure for a long time,resulting in the dissolution of a small amount of amylose,the unstable amorphous region of the starch,and making the starch granules easier to be enzymatically digested during the enzymolysis process.After the crystalline region is completely hydrolyzed,the crystalline region of the starch granules is further hydrolyzed,the double helix structure of the starch granules is destroyed,and the enthalpy of the starch is decreased.The smaller the concentration of the starch solution,the more the starch granules are in contact with the water,and the water molecules enter.Starch granules produce water and action inside the starch and destroy the non-crystalline areas of the starch molecules.Excessive enzymolysis causes the starch granules to disintegrate,and the enthalpy decreases.（8）The results of RVA show that the viscosity parameters of porous starch prepared by enzymolysis and ultra-high pressure assisted hydrolysis are all significantly lower than those of native starch.As the pressure level increases,the viscosity parameters of porous starch gradually decrease;The viscosity of the porous starch is smaller;the smaller the concentration of the starch solution,the smaller the viscosity of the starch,indicating that the ultra-high pressure treatment reduces the shear resistance of the starch.These results can show that different pressures,dwell time,starch concentration on the porous starch The viscosity properties have a significant effect.In a word,the ultra-high pressure assisted enzymolysis can reduce the amount of enzyme added by half and the time of the enzymolysis reaction by 4 hours compared with the enzymatic preparation of porous starch.The porous starch with the same adsorption efficiency as the enzymolyzed starch can be obtained,and the ultra-high pressure can be better.Promote the enzymolysis reaction to obtain porous starch with larger pore diameter and better pore-forming effect.