Study On The Invitro Activity Of Dietary Fiber In Bamboo Shoots And Composition Changes

Bamboo shoot is the enlarged buds of bamboo.It is rich in nutrients,including cellulose,amino acids,minerals,protein,vitamins,etc.Dietary fiber in bamboo shoots can be divided into soluble dietary fiber(SDF)and insoluble dietary fiber(IDF).This study analyzed the differences in physical and chemical characteristics and microscopic characteristics of five bamboo shoot dietary fibers,and explored the effects of insoluble dietary fiber on human intestinal flora and short-chain fatty acid content after in vitro fermentation.In addition,this article also studied the changes in enzyme activity and the expression of related genes related to dietary fiber content and components.The main findings are as follows:(1)In this study,enzyme extractable soluble dietary fiber and insoluble dietary fiber were prepared from five kinds of bamboo shoots.The insoluble dietary fiber content of Phyllostachys pubescens was 3.46%(fresh weight),and the soluble dietary fiber content of Fargesia spathacea was 1.97%(fresh weight).The insoluble dietary fiber of bamboo shoots performed better than the corresponding soluble dietary fiber in the aspects of water holding capacity,oil holding capacity,swelling capacity,and water binding capacity.Scanning electron microscopy showed that the apparent structure of insoluble dietary fiber was loose and porous,while the soluble dietary fiber was smooth and compact.This also confirmed that the absorption effect of insoluble dietary fiber was better than that of soluble dietary fiber.The soluble dietary fiber and insoluble dietary fiber of the Fargesia spathacea were significantly better than other bamboo shoots in the adsorption of cholesterol.XRD results showed that the proportion of amorphous regions in the structure of soluble dietary fiber of Fargesia spathacea was relatively high.Infrared spectroscopy showed that the content of lignin in the insoluble dietary fibers of bamboo shoots was rich and the structure was orderly.(2)The changes in the number of specific flora and short-chain fatty acid content of insoluble dietary fiber of Phyllostachys praecox were studied in vitro fermentation.The results of physiological and biochemical changes are as follows: Under 48 h and 37? anaerobic culture conditions,the insoluble dietary fiber would be continuously fermented by the intestinal flora.After 48 h of fermentation,the insoluble dietary fiber degradation rate reached 51.2%.The amount of Lactobacillus and Bifidobacterium in human intestinal flora fermentation broth has increased.The content of total bile acids in fecal ammonia in the intestine was reduced compared to the control.After 48 h of insoluble dietary fiber fermentation,acetic acid concentration in the intestinal flora is highest which was better than the control group;the content of propionic acid also increased compared with the control;The content of insoluble dietary fiber content of valeric acid,isovaleric acid,isobutyric acid,propionic acid,butyric acid and acetic acid was higher in the intestinal flora than in the control group.Although the total acid content increased after adding dietary fiber,it did not significantly change the proportion of intestinal flora fermentation products.(3)In order to explore the changes of dietary fiber in bamboo shoots,Phyllostachys praecox were stored at normal temperature(25?)and low temperature(4?)respectively,and investigate dynamic changes in the enzyme activities and relative gene expression correlated with the content and components in dietary fiber.The results showed that under normal temperature conditions,the bamboo shoots had been yellowed and rotted after being stored at 6 d;the bamboo shoots were yellowed and rotted when they were stored until the 24 d under low temperature storage conditions;when stored at normal temperature at 6 d The relative content of SDF and IDF was 48.57% and 75.72% respectively.After 24 d of low temperature storage,the relative content of SDF and IDF was 53.68% and 86.94% respectively.The physical and chemical properties of dietary fiber did not change significantly during the storage.When stored at room temperature at 6 d,the lignin content increased from 11.21 mg/g to 43.83 mg/g;when stored at low temperature for 6 d,the lignin content was 13.22 mg/g,and the lignin content increased to 26.31 mg/g at 24 d.The total amount of amino acids did not change much under low-temperature storage conditions,and it showed a slow downward trend under normal temperature conditions.On the 6 d,the amino acids decreased by 21.78% at normal temperature storage.PAL,POD,CAD and C4 H enzyme activities all showed a significant upward trend with longer storage time.The enzyme activity at room temperature storage was higher than that of low temperature storage.By reducing the bamboo shoot dietary fiber changes related enzyme activity,low temperature decrease the production of dietary fiber.In the low-temperature storage environment,as the storage time increases,the number of genes whose differential expression is down-regulated continuously increases.The degree of gene down-regulation was the most obvious when stored at 24 d,and there was slight difference between the groups of up-regulated genes.The number of up-regulated genes was relatively least when stored at 12 d.The relative expression of LAC-10,POD-10,HCT-10,CAD-10 and CCR-10 genes showed an overall upward trend at 4?,while the relative expression of COMT-10 gene has declined.