Effect Of Persimmon Powder On Breadmaking Quality And Study On Mechanism Of Persimmon Tannin-Gluten Interaction

The effect of persimmon powder on breadmaking quality,antioxidant capacity and postprandial glucose of bread was investigated in this study.The processing propertries of wheat flour enriched with different levels of persimmon powder and the mechanism of persimmon tannin-gluten interaction had been studied using Farinograph,Extensograph,Controlled Stress Rheometer,DSC,FT-IR and FT-Raman.The main results were shown as follows:1 Effect of persimmon powder on breadmaking quality,antioxidant capacity and postprandial glucose of breadPersimmon powder significantly(p<0.05)increased the antioxidant capacity of bread measured by DPPH,ABTS and FRAP assay,and the antioxidant capacity was positively correlated with the total phenol content in bread.Persimmon powder had a great impact on postprandial glucose of bread.It decreased the real-time blood glucose and AUC(Area under curve)significantly,and persimmon tannin was the key bioactive component in persimmon powder.Although the high addition of persimmon tannin enriched bread with a typical persimmon flavor,it significantly(p<0.05)decreased the baking quality of bread.For example,the specific volume,springiness,resilience and mean cell area of bread decreased significantly,and the hardness and cell density increased significantly with the enhancement of persimmon powder.While all the bread added with persimmon bread were acceptable.Bread enriched with persimmon powder was a good way of supplying dietary bioactive antioxidants,and regulating the digestion of carbohydrate in bread,as well as preventing type II Diabetes.2 Effect of persimmon powder on processing propertries of wheat flour and dough microstructurePersimmon powder significantly(p<0.05)decreased dough stability,extensibility,and increased the degree of softening index and the resistance to extension.Results of creep-recovery tests showed that persimmon powder not only decreased dough elasticity,but also increased dough viscosity,which indicated that the viscoelasticity of the dough was decreased.Although persimmon tannin was the main component of softening dough in the persimmon powder,it strengthened the wheat gluten at relatively low amount of addition.The microstructure of the dough was completely changed with the enhancement of persimmon powder.The results of SEM showed membrane-like gluten network in dough was transferred into mesh-like structure and part of the gluten protein fiber was fractured indicating the wheat gluten lack of the capacity to enmesh starch granules and hold gas.DSC results showed that persimmon powder interacted with both starch and gluten in dough.3 Mechanism of persimmon tannin-gluten interactionPersimmon tannin may affect the structure and the formation of gluten in two ways:Firstly,persimmon tannin blocked the cross-linking and aggregation of glutenin molecules by reducing disulfide bonds into free thiol and decreasing the stability of disulfide bridge,which affected the formation and viscoelasticity of wheat gluten.Secondly,the addition of persimmon tannin converted the compact gluten protein into loose structure by hydrogen bonds,leading to the gluten protein molecules(glutenin,gliadin)into a relatively "isolated" state.It was difficult for the dough enriched with persimmon tannin to form a viscoelastic gluten network under the co-function of covalent bond,hydrogen bonds,hydrophobic and so forth.Therefore,the dough showed poor viscoelastic and processing properties when the the enrichment amount of persimmon tannin was relatively high.