The Release And Nutritional Functional Properties Of Bound Polyphenols From Carrot Dietary Fiber During In Vitro Digestion And Colonic Fermentation And Its Application In Yogurt

Polyphenols are reactive secondary metabolites abundant in plants that have well-known antioxidant capacity and biological activities in prevention of chronic diseases including diabetes,obesity,inflammation.Polyphenols were divided into two categories according to their solubleness,one is free polyphenols(FPP)collected by aqueous–organic extraction,the other is bound polyphenols(BPP)remaining in the previous extract,which tightly linked to dietary fibers(DF),proteins,etc.via esters and ether covalent bonds,hydrophobic bonds and/or hydrogen interactions.The overwhelming most of researches on functional and biological properties of polyphenols tend to focus on the bioactivity of FPP,which may be just the tip of the iceberg.DF is carrier of abundant polyphenols and the potential benefits of this special substances has attracted growing attention.It is supposed that BPP associated with DF hardly released and absorbed into gastrointestinal tract.Subsequently,they arrive to large intestine,where they were fermented by bacterial flora along with DF,it is indistinct that whether the same BPP were liberated from DF under physiological conditions of digestion and what biological activities they have.Moreover,there is not exist any available study to compare the effects of different physical modified treatments on the properties of carrot soluble dietary fiber(SDFs)(microwave,ultrasonic,and high-pressure cooking treatments)and further investigate the properties of yogurts supplemented with different modified SDFs.Hence,this study investigated the composition from carrot dietary fiber and its in vivo and in vitro antioxidant activity,and researched systematically the release and metabolism of bound polyphenols from carrot dietary fiber and their potential activity under in vitro digestion and colonic fermentation,and explored the microstructural,rheological behavior and sensory property of yogurt supplemented with carrot soluble dietary fibers prepared by three physical modified treatments.1.Qualitative analysis of bound polyphenols from carrot dietary fiber(CDF-PP)was performed by ultra-performance liquid chromatography equipped with an electrospray ionization and quadrupole time-of-flight mass spectrometry(UPLC-ESI-QTOF-MS/MS).Eleven organic acids,nine hydroxybenzoic acids and derivatives,six hydroxycinnamic acids and derivatives,four phenolic alcohols and derivatives,three flavonoids and derivatives,seven esters and derivatives,two other compounds,were detected by matching their retention times,secondary mass spectrometry fragment information with authentic standards or literature data.Nine main compounds of CDF-PP were quantified by HPLC-ESI-QQQ-MS/MS.The results showed that the content of p-hydroxybenzoic acid was the highest(117.65μg/g DW),followed by vanillic acid(53.55 μg/g DW),and the lowest was gallic acid(0.71 μg/g DW).Furthermore,in vitro antioxidant activity was determined by different kinds of assays,including DPPH,ORAC,PSC,demonstrated that CDF-PP could scavenge radicals in a dose dependent manner.Moreover,CDF-PP exhibited significantly reactive oxygen species(ROS)scavenging activity in living Caenorhabditis elegans.2.The bound polyphenols released by fecal fermented process(30.43%)from CDF were higher than digested process(0.89%).26 polyphenols and their catabolites were detected,and the microbial pathways of primary polyphenols were proposed.Furthermore,the significant disintegration of sheet-like structure of CDF after in vitro fermentation compared with the digestion treatment.The released polyphenols exhibited higher antioxidant capacity and α-glucosidase inhibitory activity.The microbe community structure was regulated by fecal fermented CDF through decreasing Firmicutes to Bacteroidetes ratio,improving relative abundance(RA)of beneficial microbiota and suppressed RA of various harmful microbiota.3.Yogurt supplemented with different modified carrot soluble dietary fibers(SDF),including without treatment-SDF(W-SDF),microwave treatment-SDF(M-SDF),ultrasonic treatment-SDF(U-SDF)and high-pressure cooking treatment(H-SDF),were named as W-SDF yogurt(WY),M-SDF(MY),U-SDF(UY),H-SDF yogurt(HY)respectively.Structural and functional characteristics of SDFs were evaluated and then their effects on rheological,microstructural and sensory properties of yogurt were systematically investigated.SEM displayed that the surface of U-SDF and M-SDF were roughened with small holes.U-SDF and W-SDF possessed higher Mw,water-holding,cholesterol absorption capacities and reddish and yellowish colour.Moreover,the addition of SDFs into yogurt resulted in stabilizing of structure,increasing of viscosity,consistency index,pH,and decreasing of flow index,titratable acidity,syneresis percent.UY and WY exhibited greater stability compared with others.Additionally,UY showed the highest overall acceptability than others.