Physicochemical Properties And Polysaccharide Structure Analysis From Solid-state Fermented Wheat Bran By Fungi

Wheat bran is an available and abundant by-product of the wheat flour processing industry and is rich in various nutrients such as dietary fiber,protein,minerals,phenols and vitamins.Among them,dietary fiber,especially soluble dietary fiber(SDF),has a certain preventive effect on obesity,hypertension,diabetes,hyperlipidemia,heart disease and cardiovascular and cerebrovascular diseases.Cerebrovascular disease has a certain preventive effect.Therefore,the rational application of SDF in wheat bran has attracted more and more attention.People have focused on the study of phenolic substances in wheat bran and the methods of extrusion,crushing and enzymatic hydrolysis to improve the extraction rate of SDF,while the use of fungi solid-state fermented wheat bran to improve the extraction rate of SDF and the structure of fermented wheat bran polysaccharides have not been paid attention to.In this paper,three fungi(Isaria cicadae Miquel,Cordyceps militaris and Inonotus obliquus)were used to ferment wheat bran in solid state to improve the extraction rate of SDF,and the physicochemical properties,flavor and antioxidant activity of fermented wheat bran were determined.The fermented wheat bran polysaccharide was isolated,extracted and purified,and its structure and thermal stability were analyzed and studied.In this paper,three kinds of fungi were used for solid-state fermentation of wheat bran.The fermentation conditions were 50%water content,10%inoculum,and 27℃.With the fermentation time,the SDF extraction rate,flavonoid content,polyphenol content,alkyl resorcinol,p H,swelling capacity,water holding capacity and oil holding capacity of fermented wheat bran were measured.The change trend of strength and antioxidant capacity.The results showed that with the prolongation of fermentation time,the nutrients and antioxidant capacity of fermented wheat bran increased first and then decreased,and reached the highest value on the sixth day after comparison.Therefore,the flavor and microstructure of the fermented wheat bran on the sixth day were determined,and the flavor was analyzed by electronic nose and GC-MS.The results show that the formation of some aroma components in fermented wheat bran is beneficial to the aroma of food.The SDF of IC fermented wheat bran was extracted by water extraction and alcohol precipitation,and the protein was removed by Sevag method.The two polysaccharides,FWBP-1 and FWBP-2,were purified and analyzed by high performance liquid chromatography using an OHpak SB-805 HQ gel column.The test results show that the weight-average molecular weight of FWBP-1 is 3.62×10~6Da,and the Mw/Mn is 1.01;the weight-average molecular weight of FWBP-1 is 3.31×10~6Da,and the Mw/Mn is 1.02;indicating that FWBP-1 and FWBP-2 have better purity.The GC-MS results showed that FWBP-1 was composed of mannose,glucose and galactose with a molar percentage of 34.73:23.15:42.12;FWBP-2 was composed of mannose,glucose and galactose with a molar percentage of 41.33:23.13:35.54.FT-IR results indicated that FWBP-2 contained uronic acid.The experimental results of periodate oxidation,Smith degradation,methylation and 2D NMR showed that:FWBP-1 has T-D-α-Glcp(22.54%),1→2-α-D-Manp(14.02%),1→4,6-α-D-Galp(11.11%),1→2,3,4-β-D-Galp(28.70%)and1→2,3,4-β-D-Manp(23.64%)Five glycosidic bonds,FWBP-2 has T-D-α-Glcp(26.42%),1→2-α-D-Manp(18.04%),1→4,6-α-D-Galp(9.48%),1→2,3,4-β-D-Galp(22.39%)and1→2,3,4-β-D-Manp(23.67%)five glycosidic bonds.The triple-helix structure analysis showed that both sugars had triple-helix structure.The results of morphological analysis confirmed that the surface structures of FWBP-1 and FWBP-2 were different.The surface of FWBP-1 was composed of sheets and strips,while the surface of FWBP-2 was composed of rod-shaped and spherical particles.