Technology for extracting and preparing high-purity raffinose from defatted wheat germ

A process for preparing high-purity raffinose from defatted wheat germ, the method comprising the following steps:

• (1) conducting percolation extraction of the defatted wheat germ using aqueous alcohol, and collecting percolate containing raffinose, wherein the percolation extraction comprises the following sub-steps:
• loading percolation columns with the defatted wheat germ, then adding aqueous alcohol with a volume concentration of 60%˜90%, percolating 20˜60 minutes at 40˜80° C. at constant pressure continuously with a flow velocity at 0.5˜3 times of the volume of defatted wheat germ every hour, and collecting percolate containing raffinose at an exit until the volume of percolate being 3˜5 times of the volume of the defatted wheat germ;
• (2) concentrating percolate of the step (1) to remove alcohol, dissolving solid substance in deionized water followed by filtering to remove insoluble substance, extracting the filtrate with an organic solvent and concentrating an aqueous phase to obtain a decolored solution, wherein the volume of solution after the dissolving solid substance is 15%˜35% of the percolate volume;
• (3) processing the decolored solution of the step (2) through a microporous membrane of a drainage, diluting the processed solution with water to obtain a pretreatment liquid with 50˜150 mg/mL solid concentration, and desalinating the pretreatment liquid by electrodialysis to obtain a desalination solution, wherein the process of the electrodialysis consists of the steps of:
• circulating the pretreatment liquid as concentrated phase, pure water as diluted phase and Na2SO4 polar water in an electrodialysis instrument and desalinating for 2˜3 hours under constant voltage and velocity, wherein the mass concentration of Na2SO4 is 3%˜8% and the volume ratio among the polar water, the pretreatment liquid and pure water is 0.25:1:(1˜3);
• (4) separating the desalination solution of the step (3) with a simulated moving bed, and collecting flow material containing raffinose, followed by concentrating to obtain a supersaturated syrup, wherein the simulated moving bed equipment has four areas, containing 2˜4 chromatographic column in each area, wherein the fixed-bed adsorbent of the chromatographic column is acidic (Ca) ion exchange resin or (Na) ion exchange resin, using water as an eluent;
• wherein the adsorbent has crosslinking degree of 2%˜8% and pore size is 100˜400 mesh;
• wherein the operation conditions of the simulated moving bed equipment:
• the switching time is 30˜90 seconds, and velocities of flow in area I, area II, area III and area IV are 0.67˜0.86, 0.44˜0.70, 0.47˜0.79 and 0.41˜0.60 mL/min, respectively;
• and wherein isothermal operation is used in the simulated moving bed equipment and the column temperature is 60˜80° C.;
• and
• (5) crystallizing the supersaturated syrup, followed by drying to obtain white crystallized raffinose, wherein the process of the crystallization comprises the steps of:
• dissolving the supersaturated syrup of the step (4) in alcohol at 60˜90° C., and then reducing temperature to 25˜40° C., inducing crystallization by adding some raffinose, filtering after crystallizing for 12˜36 hours, and obtaining pure raffinose with a purity of 98% or higher after drying in a vacuum oven at 30˜50° C.