Inhibition Of Rutin And Quercetin On The Digestion Of Buckwheat Starches And Dried Noodles In Vitro

Low-glycaemic index(GI)diet can effectively prevent the development of chronic diseases,such as diabetes,cardiovascular disease and obesity.Buckwheat,as a low-GI food material,has received increased attention for its nutritional benefits.Polyphenols(rutin and quercetin),as the main active substances in buckwheat,have been reported to significantly inhibit starch digestion.Importantly,the current researches were mostly carried out from the perspective of inhibition on enzymes,and few researches were focused on the effect of starch structure and the interaction between starch and polyphenols.Therefore,the relationships between the fine structure of starch and the inhibitory effects of polyphenols on the digestion of starch in vitro were analyzed in this study.And the interactions between polyphenols and starch were also investigated.The inhibitory mechanism of polyphenols inhibiting starch digestion was explored from the perspective of starch structure and the interaction.On this basis,the effects of rutin and quercetin on the digestion and quality of noodles were furtherly analyzed in vitro.The results may help to provide theoretical basis and contribute to the application of polyphenols in low-GI noodles.The main contents and results were as follows:(1)The inhibition of rutin on the digestion of different Tartary-buckwheat starches was analyzed via an in vitro digestion model.The relationship between the starch fine structure and digestion inhibition on different Tartary-buckwheat starches was then investigated.And the interaction between rutin and starch was analyzed by measuring the transparency of the gelatinized starch solutions.The results showed that there was no significant difference of the inhibition of starch digestion among the Tartary buckwheat,common buckwheat and wheat with rutin addition.However,considerable differences in digestion were observed among different Tartary-buckwheat starches.The inhibitory effects of rutin on starch digestion were negatively correlated with the content of long amylose chains,but positively correlated with that of short amylose chains and amylopectin chains(p<0.05).Rutin was easily to interact waith short amylose chains during cooking.Both the inhibition on the digestion of Heifeng-NO.1(TS1)and the interaction were strongest when 2%of rutin was added.Therefore,starch fine structure mainly led to the difference in the inhibition of rutin on starch digestion in vitro.There was an optimal amount of rutin addition to inhibit starch digestion.The interaction between rutin and starch was one of the mechanisms explained the inhibition of rutin on starch digestion.(2)The inhibition of rutin and quercetin on the digestion of different starches from Tartary buckwheat was investigated in vitro.The interaction between polyphenols and starch was then analyzed by measuring the physical and chemical properties of the starch,such as iodine binding capacity,transparency,and Fourier transform infrared spectroscopy.There was no significant difference in the inhibitory effect on the digestion of TS1 between rutin and quercetin in vitro after 2%polyphenols were added.However,quercetin exists stronger and inhibitory effect on the starch digestion than rutin in other experimental groups.The influences of rutin and quercetin on the absorbance of the starch-iodine solution were strongest in the 540 nm?660 nm(p<0.05).The thermal behavior of polyphenols-starch complex was assessed using Differential Scanning Calorimetry(DSC),and no significant endothermic peaks were observed during the range of 20??150?.The formation of hydrogen bonds between starch and polyphenols was confirmed by a slowing and shifting phenomenon around3428?3197 cm^-1 in FT-IR spectra.And these changes were more obvious after rutin addition.The influnce of polyphenols on the transparency of gelatinized starch solution was attributed to both the types of starch and polyphenols and its ratio.Therefore,the interaction between polyphenols and starch affected the inhibition on starch digestion,significantly,which was one of the main reasons to display the difference in the inhibition of starch digestion by rutin and quercetin under different conditions.Importantly,rutin was easier to interact with starch(mainly amylose)through hydrogen bonds as compared with quercetin.(3)The recombinant noodles were made by mixing rutin and gluten with tartary buckwheat starch or wheat starch.The inhibition of rutin on digestibility of different noodles was then investigated.The fortified noodles were made by adding rutin or quercetin to wheat flour.And then the digestibility,qualities and starch pasting properties of enhanced noodles were analyzed.There was no significant in the digestion of noodles between wheat starch and buckwheat starch reconstituted noodles under 2.5%and 5%rutin fortification.The differences between the rutin and quercetin enhanced noodles were relatively small when polyphenols were added at 1%-3%.But the inhibition of quercetin on digestion of noodles was significantly stronger than that of rutin when the addition amount was above 3%.The optimal addition of rutin was 3%,but the stronger inhibition effect on digestion of cooked noodles after higher amount of quercetin was added.There was no significant difference between e GI value of 3%quercetin fortified noodles with that of 70%buckwheat noodles.The processing quality of both rutin and quercetin fortified noodles could meet the industrial production requirements of noodles.And the cooking quality and eating quality of the fortified noodles were significantly better than those of miscellaneous grain noodles(p<0.05).Besides,the effect of rutin on the quality of noodles was significantly lower than that of quercetin.Therefore,wheat flour can be used to replace buckwheat flour to produce low-GI noodles with rutin or quercetin addition.And the quality of fortified noodles was significantly better than commercially miscellaneous grain noodles.