| Studies have shown that dietary fiber(DF)has a positive impact on health by reducing the risk of a number of chronic diseases.Numerous epidemiological studies have consistently found that high dietary fiber intake is associated with a reduced risk of cardiovascular disease,type 2 diabetes,and colorectal cancer.However,they are still not consumed enough in the human diet.New high-fiber ingredients may make it easier for consumers to increase their fiber intake.Fruits,vegetables,grains and legumes are rich sources of dietary fiber.Dietary fiber,especially from grains,is ubiquitous in our diet.The flaxseed shell is a fibrous by-product of the flaxseed oil industry,which is usually used as feed or discarded directly.With the increasing demand for flaxseed,a large number of flaxseed shells have been discarded,resulting in considerable waste of resources and environmental problems.In this paper,flaxseed shell was used as the research material,and different particle sizes of flaxseed shell powder were obtained by ultrafine grinding.The physical and chemical properties and functional characteristics of flaxseed shell powder with different granularity were preliminarily studied.The effects of different particle sizes of shell powder on bread baking characteristics were studied.The characteristics of in vitro digestion and fermentation of flaxseed polysaccharide in shell powder and the effects on intestinal flora were discussed.The main findings are as follows:(1)Superfine grinding can significantly reduce the particle size of the powder,and the D50 decreases from 231 μm to 9.26 μm.The Brunauer-Emmett-Teller(BET)of ultrafine powder increases with the decrease of particle size.The BET of ultrafine powder increases by about 5 times compared with that of coarse powder.Crystallinity index(CI)increases first and then decreases with the decrease of particle size,and the maximum value is at SG3.With the decrease of particle size,L*value increased significantly,while B * value and A * value decreased,indicating that the color variable of the powder became pale.Compared with OS,the Oil holding capacity(OHC)of ultrafine powders decreased by about 1.66 times,while Water solubility index(WSI)increased slightly,but the changes between the superfine powders are not significant(P>0.05).As the particle size decreases,Water holding capacity(WHC)and Swelling capacity(SC)both increase first and then decrease.SG5 has the largest WHC,and SC has the largest in SG3.The intrinsic viscosity and apparent viscosity of shell powder decreased significantly with the decrease of particle size(P<0.05),and the apparent viscosity of coarse powder was the lowest.The apparent viscosity of P-OS was the lowest,and the apparent viscosity of polysaccharides extracted from the ultrafine flaxseed shell powder decreased significantly with the decrease of the particle size of shell powder.In addition,the monosaccharide composition of the polysaccharide extracted from different particle sizes of flaxseed hull powder changed,and the molecular weight distribution of the polysaccharide was quite different.(2)Compared with the coarse powder,the dissolution rate of phenolic substances in the ultrafine flaxseed shell powder was significantly increased.The extraction yield of polyphenols was almost twice that of crude powder(OS),but there was no significant difference between ultrafine powder(P>0.05).Superfine grinding significantly promoted the dissolution of lignans,and the extraction rate reached the maximum of 5.06 mg/g after 3h grinding.The finer flaxseed shell powder extract had stronger antioxidant activity in vitro.The IC50 value of sample SG9 to clear DPPH is the lowest,which is 1.03 mg/m L.The IC50 value of sample SG7 to clear ABTS is the lowest,71.89 ug/m L,and when the average particle size is less than or equal to 11.12 μm,the in vitro antioxidant activity of shell powder is the best.In terms of in vitro hypoglycemic activity,the glucose adsorption capacity and dialysis delay index of ultrafine powder were significantly higher than those of coarse powder.Shell powder crushed for 5 hours has the best glucose absorption capacity,and the maximum dialysis delay index reaches30.11%.When the average particle size was 23.44～14.96 μm,shell powder had the best hypoglycemic activity in vitro.(3)When dietary fiber of flaxseed shell was added,the specific volume,cohesion,resilience and elasticity of bread were significantly decreased,while the hardness and chewability of bread were significantly increased(P<0.05).Compared with the addition of flaxseed shell coarse flour,the addition of ultramicron flour had little effect on the specific volume,hardness,chewability,cohesion,resilience and elasticity of bread.Compared with the addition of coarse flour,the L* of the bread with the addition of superfine powder increased,and the a* and b* decreased,indicating that the color of the bread became brighter and lighter.Coarse flour has the lowest sensory evaluation score.Choosing the crust flour crushed for 3h(SG3)to add to the bread has little effect on the bread quality and is generally within the acceptable range.(4)Flaxseed polysaccharides were studied by simulated digestion(saliva,simulated gastric juice and intestinal juice)and in vitro fermentation,and the effects of Flaxseed polysaccharides on intestinal microflora were studied using high-throughput sequencing technology.The results showed that the upper digestive tract had no effect on Flaxseed polysaccharide(FSP),and the molecular weight and reducing sugar content of FSP did not change.FSP could not be digested by digestive juice from gastrointestinal tract and could reach the large intestine safely.After FSP anaerobic fermentation,the p H of the system decreased significantly,the concentration of total carbohydrates decreased significantly,and the concentration of reducing sugar increased first and then decreased.The total amount of short chain fatty acids(SCFA)increased significantly,and butyric acid,propionic acid and acetic acid were the main components.16 S r RNA analysis showed that there were significant differences in intestinal microbial community structure between FSP treatment and control group.FSP fermentation significantly reduced the ratio of Firmicutes/Bacteroidetes(F/B),and increased the relative abundance of Phascolarctobacterium,Clostridium,Sutterella,Ruminococcus and Bautia.The results showed that FSP significantly altered the composition of intestinal flora and could be developed as a functional food beneficial to intestinal health. |
PDF Full Text Request