Effects Of Rutin And Querctin On The Physicochemical Properties Of Tartary

Food is a complex system co-existed with various components,and the interactions of these components will affect the structures and functions of food matrixes,thus posing influences on the colors,flavors,nutritions and textures of food system.Phenolic compounds have been reported to enable to interact with starch,thus affecting the physicochemical properties of starch,including gelatinization properties,retrogradation properties,processing properties and in vitro digestibilities,which plays a critical role in regulation the producting and nutritional qualities of starch-based products.Tartary buckwheat is a great source for functional foods with high contents of polyphenols.Rutin and quercetin are the most representative phenols and responsible for the bioactive function in the Tartary buckwheat flour and products,while starch is the most predominant constituent of Tartary buckwheat flour and plays a significant role in the processing of Tartary buckwheat products.These two components are supposed to interact with each other in the Tartary buckwheat food matrix during processing thus changing the physicochemical properties of Tartary buckwheat starch(TBS),including gelatinization properties,retrogradation properties,rheological properties and in vitro digestive properties.The studies involved with phenol-starch interactions and their effects on physicochemical properties of Tartary buckwheat starch can give us some positive guidances on improving the processing properties and nutrition properties of Tartary buckwheat.Therefore,in our study,we chose the two most representative phenols in Tartary buckwheat—rutin and quercetin,and evaluated their effects on physicochemical properties of Tartary buckwheat starch in a model system and analyzed the interaction between phenols and starch.The main conclusions are as follows:(1)Rutin and quercetin significantly reduced the peak and final temperatures and enthalpy of TBS during gelatinization,but these reductions in T_P(by 1.0°C and 1.3°C in average,respectively),T_c(by 4.3°C and 4.5°C in average,respectively),andΔH(by 3.8 J/g and 3.9 J/g in average,respectively)were independent with the concentrations of two additives.(2)Rutin and quercetin significantly increased the trough and final viscosity,whereas reduced the breakdown value(by 23-34 RVU and 20-32 RVU respectively,compared to the control),indicating that these two additives can maintain the thermostability of paste.These two phenols also reduced the luminousness of TBS paste,which indicated that two additives facilitated the cross-linking of starch granules.The morphology of gelatinized TBS was altered with the presence of rutin and quercetin,which tended to form a crossed flaky structure.(3)The iodine-binding capacity of TBS showed no significant difference co-cooked with rutin and quercein,which implied that the interaction between rutin/quercetin and TBS was physically weak-binding force.(4)Rutin and quercetin increased the aging temperatures while reduced the aging enthalpy of TBS(by 4.8~5.0 J/g and 3.7~4.6 J/g,respectively)compared to the control,indicating that rutin and quercetin significantly retarded the retrogradation of TBS.But the crystallization of starch was not affected.The texture analysis showed that rutin and quercetin dramatically reduced the hardness and cohesiveness while increased the adhesiveness of starch gels.Improved water-holding capacities of starch gels co-cooked with two additives were observed in LF-NMR test,and rutin and quercetin greatly altered the morphology of TBS gels,which could help to develop a looser gel matrix with larger cavities compared to native TBS gels.(5)Rutin and quercetin lowered the swelling power of TBS,while improved freeze-thaw stability of TBS.Additionally,two additives increased the yield stress and consistency coefficient,decreased flow behavior index and the areas of thixotropic circles,improved the viscosity,elasticity and structural stability of starch matrix.(6)The in vitro digestibility of starch showed that rutin had no significant effect on the digestibility of TBS under given concentration,and quercetin was found to increase RS contents by 30.4%-77.2%compared to the control.