Study On Soluble Dietary Fiber And Properties Of Soybean Residue Extracted By Combined Fermentation And Ultrasound

Okara is often discarded as a by-product of soybean processing,resulting in waste of resources and even environmental pollution.But okara is rich in nutrients and rich in "seventh nutrient" dietary fiber.Okara dietary fiber contains insoluble dietary fiber(IDF)and soluble dietary fiber(SDF).The functionality of soluble dietary fiber is better than that of insoluble dietary fiber to a certain extent,but most of the dietary fiber in okara is insoluble dietary fiber,and the content of soluble dietary fiber is low.Therefore,increasing the proportion of soluble dietary fiber in okara dietary fiber has great development prospects.In this paper,fresh okara was used as raw materials to study and optimize the extraction process of water-soluble dietary fiber from okara by fermentation and ultrasonic treatment.Water-soluble dietary fiber,water-soluble dietary fiber extracted from okara after fermentation treatment,and water-soluble dietary fiber prepared by fermentation-ultrasonic combined treatment are SDF1,SDF2,SDF3,and SDF4,respectively.A comparative study of the properties and structural characterization of these four SDFs was carried out.In addition,the soluble dietary fiber prepared by the combined method is added to the biscuits to strengthen the nutrition of the biscuits.The result is as follows:(1)Preparation of okara soluble dietary fiberAfter the optimization of single factor experiment and orthogonal experiment,the optimal process for preparing soluble dietary fiber by fermentation-ultrasonic combined treatment can be determined.Under this optimal process,the average extraction rate of okara soluble dietary fiber was 18.06%;the extraction rate of untreated blank group okara SDF was 5.86±0.08%;the extraction rate of okara SDF after combined treatment was the original three times,which indicated that fermentation-ultrasonic treatment could significantly increase the content of SDF in okara.(2)Study on the structure of okara soluble dietary fiberThe particle size of SDF was measured,and the particle sizes of the four SDFs were SDF1>SDF3>SDF2>SDF4.Different treatment methods caused different degrees of damage to the structure of dietary fiber;in the infrared spectrum of SDF,it can be found that 3272,Absorption peaks were detected around 2925,1631,1540,1400 and 1035 cm-1,which are characteristic peaks of polysaccharides,among which the peak width of 3272 cm-1 changed,mainly due to the mechanism of ultrasonic and fermentation to destroy dietary fiber.More intermolecular hydrogen bonds,and the generation of new polysaccharide structures,resulting in the change of the peak position at 1035cm-1;in the X-ray diffraction pattern,it can be found that four SDFs have diffraction peaks near 2?=22°,indicating that the crystal structures of the four SDFs are similar,and they all have the cellulose type I crystal structure.In the DSC spectrum,it can be found that the position of the treated SDF peak has shifted,indicating that the binding ability of the treated dietary fiber to water is reduced,which is due to the destruction of the integrity of the dietary fiber particles;in the ultraviolet spectrum,four can be found.All kinds of SDF have absorption peaks around 200 nm,which are the absorption peaks of polysaccharides.(3)Functional study of okara soluble dietary fiberAfter measuring the functional properties of SDF,it can be found that the water holding capacity,oil holding capacity,swelling capacity,glucose adsorption capacity and cholesterol adsorption capacity of the treated SDF will be improved.Among them,the effect of ultrasound on the oil holding capacity of SDF is not significant;and the effect of ultrasound on the absorption of cholesterol is not obvious at pH=2(simulating gastric environment),and the cholesterol adsorption capacity of SDF is at pH= The absorption effect at 2(simulating the stomach environment)is smaller than that at pH=7(simulating the intestinal environment).The water retention capacity did not change significantly after the single factor treatment,but the water retention capacity increased significantly after the combined treatment.After joint processing,various properties of SDF have been improved to the greatest extent.(4)Production of biscuits containing SDFBiscuits without SDF,biscuits with control SDF,and biscuits with SDF after combined treatment were made,after texture measurement(hardness and chewiness),and sensory evaluation.There was no significant difference in the texture of the three biscuits,but the biscuits with the co-processed SDF had better color and texture.