Processing Technique And Characterization Of Tartary Buckwheat Starch-Quercetin Composite

Buckwheat is a pseudo-grass plant of genus Fagopyrum in the buckwheat family,belongingtograincrop.InChinese medicinedictionary,it's calledas“drug homologous food”.Fagopyrum tataricum Gaertner is one of the main cultivars of buckwheat and rich in polyphenols such as rutin and quercetin.It attracts wide attention due to its health functions such as antioxidant,hypolipidemic and hypoglycemic.During the processing of Tartary Buckwheat,the interaction between Tartary buckwheat starch and flavonoids can affect its physicochemical property and functional characteristics,while the mechanism is still unclear.In this thesis,Tartary buckwheat starch and quercetin were used as experimental materials,so as to explore the optimum hydrothermal conditions for the preparation of Tartary Buckwheat starch-quercetin composite.In order to provide reference for the development and production of functional products of Tartary buckwheat,Tartary Buckwheat Starch-Quercetin composite with quercetin concentration of 2.5%,5.0%,7.5%and 10.0%were prepared,its structural characteristics were analyzed via scanning electron microscopy?SEM?,X-ray diffraction?XRD?,Fourier near infrared spectroscopy?FT-IR?,and the effects of different compound degree on the aging,rheological and digestive characteristicsofTartarybuckwheatstarchweredetermined.The main contributions of this work were as follows:?1?The optimum preparation process of Tartary Buckwheat starch-quercetin composite was as follows:reaction temperature was 70?;the solid-liquid ratio was 1:10;concentration of quercetin 10.0%;water bath time was 1.5 h;pre-gelatinization time was 10 min.Under above condition,the composite rate of Tartary buckwheat starch and quercetin was 37.3%.In addition,with the addition rate of quercetin increased the recombination rate increased.Among them,the complex ratio of quercetin to tartary buckwheat starch-quercetin was26.8%,31.4%and 35.1%,when quercetin concentration was 2.5%,5.0%and 7.5%.?2?In this study,quercetin bound to the surface of Tartary buckwheat starch through hydrogen bond.The SEM results showed that quercetin attached to the surface of Tartary buckwheat starch granules.With the increase of quercetin concentration,more quercetin fused with starch granules,which increased the cross-linking between starch granules.There was no V-type characteristic peak in XRD,but there was a special peak at 2?=27.5o,indicating that quercetin did not combine to the inner helix of amylose from Tartary buckwheat,but only recombine to the outer helix of amylose and some amylopectin.In FT-IR spectra,no new peaks appeared in Tartary Buckwheat starch-quercetin composite,but with the increase of quercetin concentration,the stretching of peaks at 3500³000 cm^-1became wider,indicating that hydrogen bond was the main interacting force.When the quercetin concentration increased from 0.0%to 7.5%,the decomposition temperature of the Tartary buckwheat starch-quercetin composite increased from 310?to 318?,suggesting that the addition of quercetin could improve the stability of starch structure.?3?During processing,the transparency of Tartary buckwheat starch continued to decline.When the concentration of quercetin was lower than 5.0%,the decrease of transparency of Tartary buckwheat starch was accelerated.When the concentration of quercetin was higher than 5.0%,the result was opposite.Therefore,the transparency of Tartary buckwheat starch could be maintained by increasing the concentration of quercetin.In addition,the combination of Tartary buckwheat starch and quercetin could significantly reduce the solubility,swelling and water absorption of starch,and increased the freeze-thaw stability and oil absorption of starch,indicating that the interaction between Tartary buckwheat starch and quercetin could inhibit the aging,dissolution and expansion of Tartary buckwheat starch.The Tartary buckwheat starch after gelatinized was pseudoplastic fluid with the shear-thinning nature.The compound of tartary buckwheat starch and quercetin improved the stability,shearing resistance,elasticity and viscosity of Tartary Buckwheat starch.When the concentration of quercetin was 10.0%,Tartary buckwheat starch showed the highest shearing resistance.?4?In this study,the compound of Tartary buckwheat starch and quercetin could inhibit the digestive characteristics of Tartary Buckwheat starch,and the higher the degree of compound,the more obvious for the inhibition.When quercetin concentration increased from2.5%to 10.0%,compared with pre-gelatinized starch,the digestibility of Tartary Buckwheat starch-quercetin composite was decreased by 3.0-13.4%,rapidly digestible starch?RDS?content was decreased by 2.3-12.7%,and resistant starch content was increased by3.1-13.5%.The above results indicate that hydrogen bond was the main acting force between co-gelatinization of Tartary buckwheat starch and quercetin during.The degree of compounding was directly related with time,temperature,quercetin concentration and pre-gelatinization time,and significantly affected the processing and digestive characteristics of Tartary Buckwheat starch.Compared with the pre-gelatinized starch,the Tartary buckwheat starch and quercetin composite had higher thermal stability and non-aging,which was difficult to digest.This provided basic support for development of Tartary Buckwheat food.