| Starch,widely found in rice,is an important source of energy for the human body.Indica rice,a traditional staple food in China,is an important variety of rice.In recent years,indica rice has attracted attention because it is easily digested quickly in the intestine and affects the regulation of blood sugar in the human body.Resistant starch can regulate human blood sugar by reducing the decomposition rate of starchy foods in the small intestine,and then regulating the blood glucose response.After entering the colon,it can be decomposed and utilized by the intestinal flora to produce small molecular metabolites such as short-chain fatty acids,amino acids,ceramides,etc.,which can reshape the host intestinal flora and have a protective effect on the intestinal tract.The formation of resistant starch with different structures is closely related to the natural varieties and processing methods,and these factors also affect the way resistant starch is used in human body.At present,studies on different types of resistant indica rice starch mainly focus on the structure and digestive characteristics.However,there are few studies on the fermentation of resistant indica rice starch in intestinal tract,its effect on intestinal flora,and its relationship with starch structure and digestion.This topic mainly studies the physical and chemical structure,degradation process and products,and intestinal flora characteristics of different types of resistant indica rice starch formed by different cooking methods in the simulated digestive tract environment in vitro.Firstly,the preparation conditions of different resistant indica rice starches were determined with the content of resistant starch as a factor,and its physical and chemical structural properties such as fine structure and long-short-range order were characterized by XRD,SEM,FT-IR and other instruments.Then,the in vitro simulated digestion and simulated colonic fermentation models were used to study the digestion process of resistant indica rice starch in the human body,the production of glucose and short-chain fatty acids was measured,and a kinetic model was introduced to characterize the digestion and fermentation characteristics of resistant indica rice starch;Characterize structural changes during the process.Finally,16 S r DNA was used to characterize the changes of intestinal flora during the simulated fermentation process,so as to study the corresponding relationship between resistant starch structure-starch human digestion-colon flora change-human health benefits,and the physiological function of resistant indica rice starch The improvement of the evaluation system provides a certain reference.The research found that:(1)The intestinal digestion process of the four samples conformed to the firstorder reaction kinetic model;the LOS model showed that there were two different digestible components in the four samples;the digestion rates of RS2,RS3 and RS5 were all lower than those of IRS;RS2 The C∞ value of two natural resistant indica rice starches,IRS and RS3,was higher than that of RS3 and RS5,two artificially produced resistant indica rice starches.The fermentation of four samples mainly produced acetic acid and propionic acid.The addition of RS2,RS3 and RS5 significantly promoted the production of SCFAs and inhibited the production of isobutyric acid,while RS2 and RS5 inhibited the production of propionic acid.(2)The four samples all have different remarkable structures.The degree of polymerization and crystallinity of IRS and RS2 are higher,the crystal type is type A,and the degree of double helix of RS2,RS3 and RS5 is higher than that of IRS.After simulated digestion in vitro,all sample particles became regular crushed stones,showing V-shaped crystals;simulated digestion reduced the degree of polymerization and order of all samples,and two different particle size distributions appeared;RS2,RS3 and RS5 were in the Less ordered after digestion.After in vitro fermentation,a large number of gullies,cracks,fragments,protrusions and depressions appeared on the particle surface of all samples,and there were obvious pore structures.The simulated fermentation significantly increased the order degree of all samples and made the hydrated particle size single.RS2,RS3 and RS5 were in The orderliness after digestion is higher.(3)The in vitro simulated fermentation of IRS reduces the overall abundance and diversity of the flora,while RS2,RS3 and RS5 can improve this situation,resulting in greater changes in the overall flora and promoting the community of intestinal flora diversity.The addition of RS2,RS3,and RS5 significantly increased the abundance of Bacteroidota,Desulfobacterota,Proteobacteria,and Deferribacterota at the phylum level,and decreased the abundance of Firmicutes,Fusobacteriota,and Deinococcota;at the genus level,it significantly increased the abundance of Leuconostoc,EscherichiaShigella,and Lactiplantibacillus The abundance of probiotics such as Bifidobacterium and Bifidobacterium inhibits the abundance of Megamonas,a marker of dysbiosis.Studies have shown that resistant starch can significantly improve the structure of intestinal flora and have beneficial effects on the human body.(4)Starches with lower order degree,double helix degree and crystallinity,high hydration particle size and polymerization degree are more likely to be used by bacteria such as Bifidobacterium and Lactiplantibacillus;bacteria such as Bacillus and Escherichia-Shigella are related to the production of total SCFAs There is an obvious positive correlation,different bacterial groups in the colon use resistant starch to produce different acids;starches with lower order,double helix degree,crystallinity and digestibility tend to produce more acid in the intestine.There are more short-chain fatty acids;starch with lower particle size and DP value tends to produce short-chain fatty acids with slightly longer chains such as propionic acid,butyric acid and isobutyric acid. |
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