| Studies have shown that dietary fiber intake can prevent and alleviate common chronic diseases such as cardiovascular disease,diabetes,and colon cancer.Whole grain bran layer or bran is a good source of dietary fiber and has higher content of dietary fiber,vitamins and minerals etc.than refined grains.In this study,10 different types of bran or bran were used as experimental raw materials to extract dietary fiber(DF)from rice bran,long grain rice bran,indica rice bran,millet rice bran,wheat bran coarse bran,wheat bran fine bran,oat bran,sweet buckwheat bran powder,buckwheat bran powder,millet bran powder,etc.The physical and chemical properties,functional properties,structural properties,and in vitro fermentation properties were studied to provide a theoretical basis for the development of food products rich in cereal dietary fiber.The theoretical basis for the development of food products rich in cereal dietary fiber.The main findings are as follows:(1)Fourier transform infrared(FTIR)spectroscopy,scanning electron microscopy(SEM)and X-ray diffraction(XRD)were used to study the structural properties such as functional groups,microstructure and molecular crystallinity of 10 different types of bran or bran dietary fibers.The SEM results showed that the dietary fibers showed dense irregular lamellar shapes with more cracks and porous surfaces.The water-soluble dietary fiber(SDF)had a loose structure and lower degree of polymerization,and it was easier to form a network structure with water molecules,glucose and fat,etc.,while the insoluble dietary fiber(IDF)showed irregular folds on the surface with a large number of cracks and small pores.the XRD results showed that the crystallinity of SDF ranged from 3.15 ～ 30.85%.The highest crystallinity of millet rice bran SDF was 30.85%,and the lowest crystallinity of oat bran SDF was 3.15%.the crystallinity of IDF ranged from 5.68 ～ 26.06%.The highest degree of crystallinity of wheat bran fine bran IDF was 26.06%,and the lowest degree of crystallinity of buckwheat hull powder IDF was 5.68%.10 kinds of dietary fibers have crystalline areas.FTIR results show that the hydrogen bonding O-H stretching vibration peak near 3380.96cm-1,buckwheat bran SDF and millet bran SDF vibration amplitude is weaker than other SDF.oat bran IDF is weaker than other IDF.in the methyl group near 2930 cm-1 and methylene C-H stretching vibration peak,IDF vibration amplitude is higher than SDF.several IDF No significant differences were found.The C=O bond vibration peak of glyoxalate near 1662.17 cm-1,buckwheat bark powder SDF vibration amplitude is weaker than the other SDF.the IDF vibration amplitude is weaker than the SDF.several IDF no significant differences.In the 1115.66 cm-1 near the polysaccharide characteristic peak,millet rice bran SDF vibration amplitude higher than other SDF,buckwheat bran vibration amplitude SDF lower than other SDF.wheat bran coarse bran IDF vibration amplitude weaker than other IDF.(2)Determination of 10 kinds of bran or bran dietary fiber water-holding,oil-holding,water absorption and swelling and apparent viscosity to study their physicochemical properties.The results showed that buckwheat bran SDF had the strongest water-holding capacity,millet bran SDF had the strongest oil-holding capacity,and wheat bran fine bran SDF had the strongest water-absorbing and swelling properties.Rice bran SDF,long grain rice bran SDF,millet rice bran SDF and sweet buckwheat bark flour SDF did not have water absorption and swelling.The apparent viscosity decreased significantly with increasing shear rate of dietary fiber,indicating that all samples had shear thinning behavior.Oat bran SDF,millet bran flour SDF,wheat bran fine bran SDF,sweet buckwheat bran flour SDF apparent viscosity decline is not significant.(3)Determination of cholesterol adsorption capacity,glucose adsorption capacity,antioxidant capacity,inhibition of amylase enzyme activity and inhibition of lipase activity of 10 kinds of bran layer or bran dietary fiber to study their functional properties.The results showed that the glucose binding capacity of the 10 SDFs ranged from 56.95 ～ 432.83 mg/g.The glucose adsorption capacity of oat bran SDF was significantly higher than the other 9SDFs.the cholesterol adsorption capacity of SDF ranged from 0.41 ～ 66.21 mol/g,and the cholesterol absorption capacity of indica rice bran SDF was the strongest at 41.56 mol/g.the cholesterol absorption capacity of millet rice bran SDF was the weakest at 26.35 mol/g.the ABTS radical scavenging rate of wheat bran crude bran SDF The total antioxidant capacity of the 10 SDFs ranged from 2.00 to 5.59 μmol/g.The ability of SDF to inhibit α-amylase activity ranged from 50.16 to 86.80%,and the ability to inhibit lipase activity ranged from37.79 to 70.67%.all 10 SDFs had a high ability to inhibit enzyme activity.(4)Fermentation with manure(4)The in vitro fermentation characteristics of 10 different types of bran layers or bran dietary fibers were studied by manure fermentation method.Oligofructose was used as a positive control,and fermentation tubes without carbohydrates were used as a blank control.The strains were taken from human feces for in vitro fermentation characterization.Spot sampling tests were performed.The p H value and the content of short-chain fatty acids(SCFAs)were detected.The results showed that the p H values of the 10 dietary fibers decreased in different degrees after in vitro fermentation.in the SDF and IDF groups,the content of SCFAs in the fermentation products of all dietary fiber samples was in the order of acetic acid > propionic acid > butyric acid,in descending order.The positive control group produced higher levels of acetic acid,propionic acid,butyric acid and total acid than the 10 dietary fibers after fermentation.All DFs showed a significant increase in acetic acid,propionic acid,butyric acid and total acid content. |
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