Study On The Modification Of Sweet Potato Dietary Fiber By Compound Enzyme And The Functional Properties Of Products

In this paper,sweet potato dietary fiber(SPDF)was modified by compound enzyme,and the physical and chemical properties,microstructure,antioxidant activity of modified sweet potato dietary fiber(M-SPDF)and it's functional effects on human intestinal flora and Caenorhabditis elegans(C.elegans)were studied.It provides a scientific basis for the comprehensive utilization of sweet potato and the development of dietary fiber functional products.The main results are as follows:(1)Using sweet potato dietary fiber(SPDF)as raw material and soluble dietary fiber(SDF)yield as index,SPDF was modified by cellulase and xylanase,and the modification process was optimized by orthogonal experiment.It is concluded that the best process combination of compound enzymatic modification of sweet potato dietary fiber is as follows:the amount of cellulose is 1.2%,the amount of xylanase is 1.6%,enzymatic hydrolysis time is 30min,ratio of material to liquid is 1:11(g/mL).Under these conditions,the maximum yield of SDF is 8.84%.Compared with natural sweet potato dietary fiber,the SDF content of modified dietary fiber increased significantly.(2)The microstructure of SPDF and M-SPDF was observed by scanning electron microscope(SEM).It was found that the particles of SPDF were larger,the structure was dense,and the particles such as protein and starch were attached to the surface,while the particles of M-SPDF became smaller,the structure became loose and the pores increased obviously.Through the study of the physical and chemical properties and antioxidant activity of M-SPDF,the results showed that compared with SPDF,the water-holding capacity(WHC)and water-absorbing swelling capacity(WSC)of M-SPDF decreased significantly,but the oil-holding capacity(OHC)increased significantly.At the same time,the ability of scavenging DPPH was significantly improved,the antioxidant activity was significantly enhanced.(3)The in vitro fermentation of human faeces was studied by using SPDF and M-SPDF as substrates,fructooligosaccharides(FOS)as positive control and no carbon source as black control,respectively.The effects of M-SPDF on the function of human intestinal flora were studied by observing the changes of pH value of fermentation broth,intestinal flora and their metabolites SCFAs at different time points(0h,12h,24h,36h).The results showed that the growth of Bifidobacterium and Lactobacillus in the human feces fermentation group supplemented with MSPDF was significantly higher than that in the SPDF fermentation group,while the growth of Enterobacter and Enterococcus in the human feces fermentation group was significantly lower than that in the SPDF fermentation group.Compared with BC group,the value of pH in fermentation broth of SPDF group,M-SPDF group and FOS group decreased significantly,and after 36 h fermentation,the total content of SCFAs was M-SPDF group>SPDF group>BC group>FOS group,and the content of different SCFAs in fermentation system was acetic acid>propionic acid>butyric acid.The above results showed that the compound enzyme modification significantly enhanced the probiotic effect of sweet potato dietary fiber on intestinal flora.(4)Taking Caenorhabditis elegans(C.elegans)as model organism,the effect of M-SPDF on the lipid deposition of C.elegans was studied,and the lipid-lowering effect of M-SPDF was initially explored.The results showed that:The addition of L-SPDF,L-M-SPDF,H-SPDF and H-M-SPDF to culture C.elegans(N2)in Nematode Growth Media(NGM)culture medium could reduce the content of TG in C.elegans.The lipid-lowering ability of M-SPDF was significantly higher than that of SPDF.When the concentration of 10mg/mL was added,the triglyceride(TG)content of SPDF group and M-SPDF group decreased by 82.69%and 86.46%,respectively.These results indicate that both SPDF and M-SPDF can reduce the TG contentin C.elegans,but M-SPDF has a better effect,and this effect has a dose-dependent effect on the sample concentration.