Study On Preparation Of High-purity Phytosterol By Magnetic-induced Crystallization

Phytosterols have many physiological functions and are widely used in the fields of food,medicine,chemical industry and so on.The different purity of mixed phytosterols and monomer sterols have different applications.High purity phytosterols are mostly used in the pharmaceutical industry.High-purity monomer sterol can also be used as standard reference substance.Industrial production of high-purity phytosterols was mainly by solvent crystallization,which was time-consuming,large amount of solvent use,and uneven quality.In this study,soybean oil deodorizer distillate were used as raw materials to separate and extract phytosterols.Based on the structural and magnetic properties of sterol molecules,an external magnetic field was introduced to induce crystallization in order to improve the crystallization rate of sterol and obtain high-quality and high-purity mixed phytosterols.Based on the study of magnetic induction technology for the preparation of high-purity mixed phytosterols,combined with the difference of properties between stigmasterol and ?-sitosterol,the magnetic-induced crystallization technique was applied to the extraction of stigmasterol monomer and the added value of the product was increased.The magnetic induced crystals were characterized by scanning electron microscopy(SEM),thermal differential analysis(DSC),X-ray diffraction(XRD),fourier transform infrared spectrometry(FT-IR)and so on.The difference between magnetic induced crystallization and traditional solvent crystallization was compared.The mechanism of the magnetic field induced crystallization was verified and explored by the determination of the solubility,viscosity and surface tension of the crystallization solution system.The main results were as follows:1.The extraction of mixed phytosterols was carried out by the magnetic-induced crystallization technique.75.30% of crude sterol was obtained by the esterification pretreatment method from the soybean oil deodorizer distillate,which was used as the raw material for magnetic-induced crystallization.The optimum technological conditions were as follows: the crystallization solvent was the mixed solvent of ethyl acetate and methanol-water,the solid-liquid ratio was 1:30,the amount of the methanol water was 6%,the magnetic field strength was 0.6 T,the crystallization process was always carried out under the magnetic field condition,and the crystallization time was42 minutes.A refined mixed phytosterols with a purity of 98.43% and a recovery of91.61% can be obtained after 1 h of nourishing crystal time.Compared with the mixed phytosterol crystals without magnetic field,the crystallization time of mixed phytosterols was shortened from 96.2 min to 42.0 min,the purity of mixed phytosterols was increased from 92.50% to 98.43% and the recovery rate increased from 69.65% to91.61% under the magnetic field of 0.6T.Through the structure characterization of sterol crystal,it was found that the structure and functional group of the mixed phytosterol crystals with magnetic-induced crystallization have no change,and its melting range became shorter,the melting enthalpy was increased,the optical purity was increased and the crystallinity was increased.The results show that the magnetic field can shorten the crystallization time and improve the purity,recovery and crystal quality of sterol.2.The extraction of stigmasterol monomer was carried out by the magnetic-induced crystallization technique.86.26% crude sterol was obtained by the esterification pretreatment method from the soybean oil deodorizer distillate,which was used as the raw material for the separation of stigmasterol.The better technological conditions were as follows: the crystallization solvent was cyclohexanone,the ratio of solid-liquid ratio was 1:6,the nourishing crystal temperature was 25 ?,the nourishing crystal time was 2h.A high purity stigmasterol monomer with a purity of 98.38% and a recovery of10.29% can be obtained under the magnetic field of 0.6 T,while a high purity stigmasterol monomer of more than 98% can be obtained by double recrystallization without magnetic field.Through the structure characterization of stigmasterol monomer,it was found that the structure and functional group of the stigmasterol monomer were not changed,and the melting point of the monomer was also within a reasonable range.However,the crystallinity increases,the surface of the crystal was more compact,the melting range became shorter,the melting enthalpy was increased and melting point was increased.The results show that magnetic-induced crystallization can promote the separation of stigmasterol and ?-sitosterol,and the aggregation of stigmasterol.The crystallization time was reduced and the recovery rate was increased and the quality of stigmasterol monomer was also better.3.The solubility,viscosity and surface tension of sterol solution decrease with the increase of magnetic field intensity.The results show that the magnetic field can weaken the effect of hydrogen bond,resulting in the decrease of solubility and surface tension of the system,while the magnetic field reduces the activation energy of the solution itself and increases the internal energy of the system,which leads to the decrease of theviscosity of the system.These changes can enhance the crystallization and purification process of phytosterol.It is inferred that the increase of purity and recovery of mixed phytosterols under the action of magnetic field is related to the effect of hydrogen bond,and the increase of purity of stigmasterol monomer is related to the molecular polarity and hydrogen bond strength of different sterols.