Study On The Effect Of Thermally Induced Infiltration Of Barley ?-Glucan Microgel On Wheat Protein Aggregation And The Application

Barley accounts for the fourth largest global crop and is rich in functional beta-glucan.In recent years,studies on improving human metabolic function through diet control have been heightened.It is attributable to the increasing incidence of chronic metabolic diseases,such as coronary heart disease and type 2 diabetes.Barley ?-glucan(BBG)provides a variety of health benefits,such as lower serum cholesterol levels and attenuate postprandial blood glucose.Because of the functional activities of BBG,the U.S.Food and Drug Administration(FDA)and the European Food Safety Authority(EFSA)have approved health claims for BBG.However,BBG weaken the gluten network structure,causing a rough texture of the flour product,a sticky mouthfeel,and the volume is reduced,the color is darkened.The deterioration of the sensory quality of the flour product caused by BBG is the main limiting factor for its application in food.Therefore,to explore the mechanism of interaction between BBG and gluten protein is of great significance for the development and utilization of BBG and gluten.Firstly,BBG was obtained through the high-speed centrifugal vortex breaking(HSCV)method and the traditional method.The HSCV method can pulverize the barley cell wall during the extraction process to promote BBG dissolution,improve the extraction efficiency and shorten the extraction time.It was found that BBG solution is a pseudoplastic fluid,showing obvious shear thinning behavior,and was significantly affected by the concentration of BBG solution.Compared with the traditional extraction method,the HSCV extraction reduced the viscosity and particle size distribution of the BBG solution,and the particle content in the range of 200-500 nm reached more than 75%.Although the thermal stability of BBG extracted by the HSCV method was lowered,the HSCV method did not affect the primary structure of the BBG molecular chain.Different extraction methods influenced the rheological properties of BBG by changing the high-level structure of the BBG molecular chain and the state of molecular aggregation.The HSCV method can obviously improve the extraction efficiency of BBG and is suitable for the large-scale production of BBG.Subsequently,the effects of BBG on the pasting properties of wheat flour,the rheological properties and the thermochemical reaction process of the dough during heating were studied.The mechanism of BBG on the weakening of gluten protein was analyzed.It was found that BBG inhibited starch gelatinization at the addition of 1% to 5%,increasing the gelatinization temperature of wheat flour,and lowering its peak viscosity,tough viscosity,and final viscosity.Adding BBG to the wheat dough increased the dynamic modulus(G',G")of the dough,and tan ? showed a tendency to increase first and then decrease.During the heating process,the change of tan ? was negatively correlated with the amount of BBG addition,and BBG reduced the viscoelastic capacity of the dough after heat treatment.The different scanning calorimetry(DSC)analysis showed that the addition of BBG delayed the thermochemical reaction in the dough,and the response peaks moved to the high-temperature zone.The size exclusion-high performance liquid chromatography(SE-HPLC)results showed that the addition of BBG mainly affected the SDS extractability of glutenin and gliadin,barely affected albumin and globulin.The subunit changes of gluten were further analyzed by the sodium dodecyl sulfatepolyacrylamide gel electrophoresis(SDS-PAGE),and it was found that BBG had certain selectivity for the different molecular weight of gluten subunits.By analyzing the fluorescence microstructure of the dough during heating,it was found that BBG formed a microgel at low temperature in the dough.During heating,the BBG microgel melted and penetrated into the gluten network structure,and the thermochemical reaction process in the dough was hindered,with the starch gelatinization,protein denaturation cross-linking,etc.,delayed to higher reaction temperatures.Then,the effects of water redistribution induced by BBG on the formation of the gluten network structure were further analyzed.Rapid viscosity analysis and Mixolab results showed that BBG increased the water absorption of wheat flour and enhanced the water retention of the dough.However,the weakening degree of gluten increased and the stabilization time decreased.BBG hindered the gelatinization and retrogradation of starch in the dough.The addition of BBG increased the temperature of the weakly-bound water loss and decreased the temperature of the strong-combined water loss.Adding BBG,the total thermogravimetric analysis(TGA)mass loss of the dough was reduced by an average of 2.11%.At 50% water addition,BBG increased TGA weakly-bound water content and DSC freezable water content.However,at high water levels(60% and 70%),BBG reduced both TGA weakly-bound water content and DSC freezable water content.The low field nuclear magnetic resonance analysis(LF-NMR)results showed that at the same water addition,BBG increased the relaxation time T21 of the moisture in the dough and lowered T22.It indicated that BBG weakened the binding strength of the tightly bound water in the dough,while it enhanced the strength of the weakly-bound water in the dough so that the water distribution tended to be uniform.During the heating process,the free sulfhydryl group was activated.At a temperature below 55°C,the addition of BBG significantly reduced the concentration of free sulfhydryl groups in the dough.As the temperature continues to rise,the free sulfhydryl groups were activated,and the concentration of free sulfhydryl groups in the BBG dough decreases as the temperature increases.Finally,the direct interaction between BBG and gluten in aqueous dispersion was studied by analyzing the properties of the emulsion systems with or without extrusion.LF-NMR results showed that when excess water was added,adding BBG mainly increased the binding ability of gluten to weakly bound water in the aqueous phase.BBG significantly increased the water retention and freezable water content of extruded and raw gluten.Extrusion increased the dissolution of gluten in the homogenization process but did not increase the solubility of gluten practically.TGA analysis showed that compared with the gluten only,the thermal decomposition temperature of the BBG and gluten complex system was lower,indicating a decrease in the degree of cross-linking polymerization of gluten.The extruded BBG and gluten complex system was more uniform and finer,with higher water holding capacity,which gave the complex system a sticky taste and a chewing rebound.By weakening the gluten crosslinking with BBG and using the thickening and emulsifying properties of BBG,an innovative idea to prepare polysaccharide-gluten fat replacer was presented.