| Corn starch is a kind of low cost,green and degradable biopolymer with double helix cavity structure.The amylose molecule have a special nature of "hydropHobic inside and hydropHilic outside",which can be used as the main molecule to interact with a variety of phenolic substances with biological activity to form a phenolic acid-starch ester complex,so as to modify corn starch and give it the biological properties of phenolic acid.In this thesis,corn starch was selected to compound with ferulic acid by Novozym435 immobilized lipase catalyzed-reaction,and the substrate of the reaction was ultrasonic pretreated before the transesterification reaction.The influence of ultrasonic pretreatment substrate on the catalytic synthesis of ferulic acid starch ester was investigated,and the structure characterization and pHysicochemical properties of the product were analyzed.1.By using the substitution degree of ferulic acid starch ester as indicators,the effect of ferulic acid starch ester synthesis,the results showed that the ultrasonic pretreatment time,temperature and power were used as the single factor of the experimenton when the ultras-onic pretreatment substrate temperature was 30 min,the ultrasonic pretreatment substrate temp-erature was 60 ?,the ultrasonic pretreatment power was 600 W,ferulic acid starch ester substitution degree reached the highest value of 0.0728.Compared with the substrate without ultrasonic pretreatment,the substitutability of starch ferulic acid ester can be increased by more than 5 times.The crystalin-ity of starch was effectively degraded by ultrasonic pretreatment substrate,and ultrasonic pretreatment of the substrate can effectively degrade the crystallinity of starch,and rincrease t0,increase tc,tp and ?H.Increase,that is,ultrasonic pretreatment of the substrate can increase the amylose content in the starch molecule,increase the hot energy required to break the double helix structure of starch molecules.2.The results of structural characterization and analysis of ferulic acid starch ester were shown as follows:(1)UV spectrophotometer analysis showed that the absorption peak of the synthesized product after alkali hydrolysis was at 320 nm,while the special absorption peak of the ferulic acid standard product was at 320 nm.It was initially confirmed that ferulic acid was attached to the starch molecule.(2)FT-IR analysis showed that compared with the original corn starch,the new absorption peak of starch ferulate ester at 1728.6 cm-1 was caused by the stretching vibration of ester bond,that is,the lipase catalyzed the synthesis of starch ferulate ester.(3)nuclear magnetic resonance hydrogen spectrum testified:Ferulic acid starch ester does not appear vibration peak at the vibration peak position of ethyl ferulate,but vibration peak appears in the peak range of ethyl ferulate,which proves that the ultrasonic pretreatment substrate can be synthesized enzymatically ferulic acid starch ester.(4)SEM showed that the original corn starch has been destroyed after the ultrasonic pretreatment,ther is a depression and aperture,and a large number of ferulic acid can entered the starch molecules through the popre produced by the surface ofthe corn starch molecule,increasing contact of the hydroxyl groups in the starch double spiral pores.In addition,the generated ferulic acid starch ester lost the original shape of the starch,the structure was completely destroyed,showed a flush tomography,and a large amount of recessed holes were generated.(5)XRD analysis showed that the crystal form of the original corn starch was converted from type A to a V-type,and the phenolic acid inclusion complex was formed.(6)DSC showed that the t0,tp,tc and ?H of raw corn starch after ultrasonic pretreatment and enzyme-catalyzed synthesis of ferulic acid starch ester.Its rise is much greater than the change in starch thermal characteristics after the ultrasonic pretreatment substrate,that is,the change of enzyme catalysis on the thermal properties of starch is greater than the effect of ultrasonic pretreatment substrate on starch.3.Ferulic acid starch ester pHysical and chemical properties analysis were conducted.Compared with the original corn starch,the DPPH radical scavenging rate,water holding rate,enzyme resistant starch content,solubility and swelling degree of the ferulic acid starch ester prepared by ultrasonic pretreatment of substrate were increased by 4.69%,26.2%,13.86%,4.12%,3.53%respectively.But the drainage rate decreased by 2.6%,while the viscosity and iodine absorption capacity were lower than that of of the original corn starch.It is concluded that ferulic starch ester synthesized by ultrasonic pretreatment substrate has the physical and chemical properties of higher water holding,higher enzymatic hydrolysis resistance,relatively high swelling degree,lower viscosity and stronger freeze-thaw resistance. |
PDF Full Text Request