Preparation Mechanism Of Dietary Fibre From Soybean Okara With Submerged Fermentation

In this study,the difference of soybean okara dietary fibre prodution fermented by fine breeds of edible fungi was investigated.Depand on the best edible fungi breed,the effects of culcure medium and fermentation conditions on the content of soluble dietary fibre(SDFs)and the quality of dietary fibre was investigated.The compositions and structures of SDFs were analyzed by UV,IR and HPLC.The biological activities of SDFs were studied,their antioxidant activities were compared.The physical and chemical properties of IDFs were studied.Finally,the changes of the fermented IDFs in different particle size processed by super fine crushing were researched.The main results and findings were shown as follows:1.The enzymes produced by liquid state fermentation of edible fungi and their effects on the main nutrients of soybean okara were studied.Results showed that there were statistically significant differences in the growth speeds and enzyme properties among different edible fungis.Pleurotus ostreatus has the fast growth rate and high protein availability,as well as higher activity of exo-1,4-β-D-glucanase,lower activity of endo-1,4-β-D-glucanase and β-1,4-D-glucosidase,which led the increased content of SDF to 20.49%.It showed significant difference from the other four kinds of edible fungis,and the content of SDF was 4.39 times higher than soybean okara.2.Effects of VB1 and inorganic salt on the content of SDF and the quality of DF were investigated.Results showed that the KH2PO4,FeSO4 and VB1 influenced the content of SDF and the quality of DF positively as well as the MgSO4 and CaCl2 influenced the content of SDF and the quality of DF negatively.The optimal fermentation medium was determined:of 8 g/L KH2PO4,0.6 g/L FeSO4 and 0.8 g/L VB1 in soybean okara of 30g/L.3.The culture conditions of fermentation temperature,fermentation time and inoculum quantity influenced the content of SDF and the quality of DF effectively.The influence of fermentation temperature,time and inoculum quantity all curves fitted well with Guass equation.By the analyzing results,the optimal culture condition was obtained.Under the condition of fermentation temperature 19 ℃,fermentation time 8 d and inoculum quantity 13%,the most content of SDF and the best quality DF was obtained.4.The molecular weight of SDFs was analyzed by high performance size exdusion chromatography(HPSEC).The soybean okara SDF contained two main parts which molecular weight was 198.87 kD and 5.32 kD.The fermented soybean okara SDF contained three main parts which molecular weight was 139.34 kD,0.95 kD and 0.03 kD.The monosaccharide compositions of SDFs were analyzed by high performance liquid chromatography(HPLC)after derivative reactions.The monosaccharide composition and molar ratio of soybean okara SDF was D-Xylose:L-Arabinose:Galacturonic acid:D-Mannose:L-Rhamnose:D-Galactose:D-Glucose:L-Fucose=3.25:2.81:2.42:2.32:2.31:2.17:2.09:0.39,but no Ribose.The monosaccharide composition and molar ratio of fermented soybean okara SDF was D-Galactose:L-Arabinose:D-Xylose:D-Mannose:L-Rhamnose:Galacturonic acid:D-Glucose = 6.37:3.43:2.65:2.35:2.20:2.15:1.95,but no L-Fucose and Ribose.With the infrared spectrums of SFDs,we found that the components of the two kinds of SDFs exhibited typical absorption peaks of sulfuric acid group and P-glycosides bond in the 4 000 cm-1～400 cm-1 range,which showed that they were polysaccharide.The results of the antioxidant capacity test showed that the reducing power and the scavenging ability of solubl on 1,1-diphenyl-2-picrylhydrazyl radicals,hydroxy radical and superoxide radicals of fermented soybean okara SDF were all stonger than soybean okara SDF.5.Using scanning electron microscope(SEM)to observe the surface morphology of the IDFs,we found that the fermented soybean okara IDF had more aperture,larger specific surface area and looser structure than the other two kinds of IDF.The water-holding power of fermented soybean okara IDF was 6.23 g/g which was 11.85%higher than soybean okara IDF.The swelling force of fermented soybean okara IDF was 6.23 g/g which was 11.85%higher than soybean okara IDF.The oil-holding power of fermented soybean okara IDF was 2.53 g/g which was 80.71%higher than soybean okara IDF.The sodium cholate adsorption capacity of fermented soybean okara IDF was the highest followed by soybean okara IDF.The cholesterol adsorption capacity of fermented soybean okara IDF and soybean okara IDF was higher at pH 7.0 than pH 2.0 and fermented soybean okara IDF was the highest followed by soybean okara IDF.As the particle size of fermented soybean okara IDF reducing,the water-holding power,swelling force and the oil-holding power of fermented soybean okara IDF all curves fitted well with Guass equation,while the sodium cholate and cholesterol adsorption capacity increased first and kept gentle then.