Effects And Mechanisms Of Dandelion Flavonoids On In Vitro Digestive Characteristics Of Potato Starch And Noodles

Starch digestion is closely related to postprandial blood glucose levels.Dietary intervention controlling blood glucose concentrations,might be an effective and economic way to reduce the incidence of type-II diabetes and co-morbidities.Many flavonoids have been shown to decrease the rate of carbohydrate digestion and absorption by inhibiting the activity of α-amylase and combining with starch to form complexes,resulting in the lower postprandial glucose response.Dandelion is rich in flavonoids,which has many physiological activities such as anti-bacterial,antioxidation,lowering blood lipid and blood glucose levels.However,the mechanism of dandelion flavonoids inhibiting pancreatic α-amylase has not been clarified,and its effect on the dynamic digestion of starchy foods in vitro are still in the preliminary stage.This dissertation mainly investigated the inhibitory effect of dandelion flavonoids on porcine pancreatic α-amylase activity and in vitro digestive and sensory properties of starch and noodles.This work has provided a quantitative basis for the application of dandelion flavonoids as a promising pancreatic α-amylase inhibitor in the development of functional foods with lower postprandial glucose response.The main conclusions are as follows:(1)Mechanistic study on inhibition of porcine pancreatic α-amylase using the flavonoids from dandelionThe dandelion flavonoids reversibly inhibited the pancreatic α-amylase in a noncompetitive manner,and showed a greater potent inhibitory effect than acarbose.The half-inhibitory concentration(IC50)values for the dandelion flavonoids and acarbose were 0.0067 and 0.019 mg/mL,respectively.The flavonoids presented a strong ability to quench the intrinsic fluorescence of α-amylase through static quenching by forming a complex.The positive values of enthalpy and entropy change indicated that the binding was predominately driven by hydrophobic interactions.(2)Effects of dandelion flavonoids on the physicochemical properties and in vitro digestion of starch pasteIn vitro static simulated digestion results showed that the hydrolysis rate of potato starch paste decreased from 94.6%to 75.8%and the fraction of resistant starch increased from 3.4%to 23.1%with the addition of dandelion flavonoids increasing from 0%to 10%.The moduli and viscosity of starch paste decreased after the addition of dandelion flavonoids.Moreover,the crystallinity of cooked starch increased significantly and the microstructure became looser with a few more starch aggregates.These results indicated that the complex formed by dandelion flavonoids and starch could inhibit starch gelatinization and thus reduce the rate of starch hydrolysis.(3)Sensory quality and in vitro static digestive characteristics of dandelion flavonoids noodlesDandelion flavonoids and wheat flour were used as main raw materials to prepare dandelion flavonoids noodles with different proportions.The SEM(Scanning Electron Microscope)results showed that the gluten network structure of noodles was more compact and continuous showing more intact starch granules with the increase of the dandelion flavonoids added.TPA(Texture Profile Analysis)analyses showed that dandelion flavonoids significantly reduced the hardness and chewability of noodles,but had no significant effect on the elasticity.The sensory tests showed that the addition of 8%dandelion flavonoids had no significant effect on the sensory acceptability of the noodles.The estimated glycemic index of noodles was 87.3%,80.2%and 76.2%when the content of flavonoids was 0%,4%and 8%,respectively.(4)In vitro dynamic digestive characteristics of dandelion flavonoids noodles based on bionic gastrointestinal systemIn order to evaluate the effect of dandelion flavonoids on digestive properties of noodles more accurately,the physical fragmentation,gastric emptying and dynamic digestion processes of noodles were simulated using an advanced bionic gastrointestinal system.Due to the digestive fluid dilution and enzymatic hydrolysis,the modulus and viscosity of both gastric and intestinal digesta decreased gradually,but the noodle added with 8%dandelion flavonoids showed significantly higher digesta modulus and viscosity than the control group(0%).Moreover,with the addition of dandelion flavonoids increasing from 0%to 8%,the half-emptying time of the noodles was increased from 74.7 min to 87.3 min,supporting the decrease of starch digestibility from 43.9%to 25.4%and protein digestibility from 79.0%to 55.1%after 180 min digestion.In addition,the effects of particle size after simulated mastication on the in vitro dynamic digestive characteristics of the flavonoids noodles were investigated.The noodles with smaller size due to the higher chewing degree emptied faster,resulted in a higher rate and extent of starch and protein hydrolysis.This suggests that the degree of mastication may be an important factor affecting the postprandial glycemic response.