Study On The Effects Of Highland Barley Flour On Dough Properties And Bread Qualities And Its Mechanisms

Highland barley,which has high nutritional value,is rich in several bioactive components such as β-glucan and polyphenolics.The bread is one of the common staple in life with good palatability and high market share.Adding highland barley flour to bread can aggrandize the nutritional value of bread and extend the industrial chain of highland barley.Using highland barley flour and high gluten wheat flour as main raw materials,this paper focused on the effects of highland barley flour on bread qualities and functional properties,meanwhile explored the interaction mechanisms between intact highland barley flour(HBF)and dough as well between de-endogenous β-glucan highland barley flour(D-β-HBF)and dough,thus providing theoretical basis for the application of highland barley flour on bread.The main conclusions obtained are as follows:(1)The influence of highland barley flour(HBF)on the quality of bread was studied by means of chromatic aberration,specific volume,texture properties and sensory evaluation.The color of bread gradually darkened as for increasing the amounts of highland barley flour.And compared with plain bread,the a* value and ΔE value of bread enhanced after adding highland barley flour.Moreover,the specific volume,elasticity,resilience and cohesiveness of bread lessened while the addition of highland barley flour augmented,and the hardness was positively correlated with additional proportions of the highland barley flour.In the meantime,the smell and taste of bread with 20% addition of highland barley flour were more favorable,as though the appearance and structure needed improvements.(2)The effects of highland barley flour(HBF)on the content of functional components,antioxidant capacity and in vitro digestibility of bread were researched.The results demonstrated that the contents of total polyphenolics,total flavonoids and β-glucan in bread had positive correlations with the addition of highland barley flour,and it could significantly elevate the scavenging ability of bread for DPPH and ABTS free radicals by adding highland barley flour.Through the results of in vitro digestion,it was indicated that highland barley flour could reduce the amounts of fast-digesting starch,the quantity of slow-digesting starch in bread was elevated on the contrary,and meanwhile the in vitro digestibility of starch in bread with 10% addition of highland barley flour was lower than that of starch in plain bread.(3)The chromatic aberration,water and oil holding capacity and gelatinization properties of the highland barley flour(HBF)blending wheat flour were analyzed.The addition of highland barley flour degraded the brightness of composite flour whereas sharpening the water and oil holding capacity.And by raising the amounts of highland barley flour,the gelatinization temperature,peak time,viscosity and setback of the composite flour reduced.(4)The effects of highland barley flour(HBF)on dough were studied by analyzing texture characteristics,microstructure and dynamic rheological properties.The hardness and resilience of composite dough heightened significantly with the increased addition of highland barley flour(p<0.05).Similarly,the results of dynamic rheological properties presented that the storage modulus(G′)and loss modulus(G″)of the composite dough gradually elevated by the incremental addition of highland barley flour.However,the network structure of gluten protein in dough gradually roughened and collapsed with the addition of highland barley flour,which was revealed by scanning electron microscope,and starch granules were damaged simultaneously.(5)The effects of highland barley flour(HBF)on gluten protein were investigated.With the increase of the highland barley flour proportions from 0% to 30%,the gluten content in the dough of composite flour(highland barley and wheat)decreased significantly(p<0.05),and the total sulfhydryl content reduced,part of the disulfide bonds were converted into free sulfhydryl groups simultaneously.In SEM results,evident cleavages were observed in the gluten network structure at 30% addition of highland barley flour.Besides,the β-sheet and α-helix structures,which were the secondary structure of gluten protein,transformed into disordered structure.And in the thermodynamic results of gluten protein,its peak temperature increased when highland barley flour was added at 10% and 20%,while which decreased at30% addition.(6)The influence of de-endogenous β-glucan highland barley flour(D-β-HBF)on the characteristics of dough was analyzed.After adding D-β-HBF into wheat flour,the peak viscosity,valley viscosity and final viscosity of mixed flour were higher than those adding highland barley flour(HBF).And the contents of total sulfhydryl group and disulfide bonds of gluten protein in dough with D-β-HBF flour blends were lower than those with HBF flour blends at the same addition.Compared with the gluten protein at the same addition of HBF in dough,D-β-HBF lessened the content of β-sheet structure in gluten protein,whereas the content of disordered structure elevated.In the meantime,the peak and final temperature of gluten protein,impaired with raised addition of D-β-HBF.The results above indicated that compared with the addition of HBF,the network structure of gluten protein in dough mixed with D-β-HBF was more unstable.