Preparation method of soluble dietary fiber prepared from lotus rhizome nodes

The invention discloses a preparation method of a kind of soluble dietary fiber prepared from lotus rhizome nodes. The preparation method comprises following steps: step A, drying lotus rhizome nodes: washing and drying fresh lotus rhizome nodes, grinding, sieving, and adjusting water content; step B, extruding and puffing: carrying out an extruding process with a double screw extruding and puffing machine; step C, extracting soluble dietary fiber by an ultrasonic-assisted alkali-enzyme method: step a, grinding the lotus rhizome node powder, which has been extruded and puffed, then sieving, dissolving the lotus rhizome node powder in water, adding alpha-amylase at the same time, and controlling the temperature in a certain range to carry out hydrolysis reactions; step b, adjusting the pH value of the liquid after hydrolysis, and placing the liquid in an ultrasonic washing machine to extract; step c, adjusting the pH value of the extract obtained in the step b, carrying out a centrifugation treatment, discarding the slag, collecting the supernate, adjusting the pH value of the supernate, adding ethanol to participate, carrying out a centrifugation treatment, filtering, and drying so as to obtain the SDF product. The preparation method has the advantages of easy and practicable method and simple operation, combines the modification through extruding and puffing and extracting method through the ultrasonic-assisted alkali-enzyme together, thus the modification time of SDF is shortened, the extraction rate of SDF is increased, and the processing property and physical and chemical properties of the product are prominently improved.