Effects Of Extrusion Processing On Smash Characteristics Of Extruded Bran And Qualities Of Whole Wheat Flour

The production and consumption of whole wheat food have attracted increasing attention and interests in the world.However,whole wheat has rough taste,short shelf life and poor food production on account of adding wheat bran.Besides,because wheat bran fiber ingredients in the majority,so the wheat bran is difficult to crush to a certain size,which limits the industrial production of whole wheat flour.Therefore,to explore suitable whole wheat flour production process and improve the quality of whole wheat flour,which has great significance to the popularization of whole-grain foods.Based on wheat bran from 3B milling roller in wheat flour milling processing and common wheat bran as raw material,the processing of backfilling whole wheat flour by extrusion were investigated.First of all,the extrusion process parameters of the two materials were optimized with the expansion ratio.Then the effect of the extrusion on crush properties and molecular structure was discussed.After that,the grinding process of roller mill was studied.Finally,backfilling whole wheat flour was prepared according to the national industry standard,and their rheological properties,flavor substances and characteristics of the steamed bun and biscuit were comparative analyzed.The main conclusions are as follows:Through the single factor and orthogonal experiment,the optimum extrusion process parameters of 3B bran were as follows: extruded temperature was 160 °C,material moisture content was 19%,screw speed-frequency was 20 HZ.Considering the phenomenon of blocking and spraying material during extrusion,the optimum extrusion process parameters of the common bran were as follows: the extruded temperature was 160 °C,the material moisture content was 23%,the screw speed-frequency was 15 HZ.Comparison the expansion ratio,common bran was much lower than 3B bran,and easily to blocking,spraying and so forth during extrusion,namely the extrusion process was very unstable.By investigating the effect of extrusion on the smashing capability and molecular structure of wheat bran,it can be found that the expansion ratio of 3B bran showed a significant correlation with the sieving rate after crushing.Through the extrusion treatment,the content of hemicellulose in 3B bran and common bran was significantly decreased,the content of cellulose was not obviously changed,and the lignin content slightly fluctuated.Moreover,the free ferulic acid,soluble covalent ferulic acid,and bound ferulic acid content had undergone significant changes.Between the two materials,the content of free ferulic acid and soluble covalent ferulic acid of 3B bran with high expansion ratio was significantly higher than common bran with low expansion ratio,while the bound ferulic acid content had an inverse relationship.The characteristic absorption peaks of the two materials were significantly changed after extrusion,and the change of 3B bran was more obvious.According to the change of the characteristic absorption peaks of common bran and 3B bran,it can be seen that the internal structure include protein,lignin and hemicellulose were changed after extrusion,and some of the ester bonds were broken.Therefore,the microstructure of 3B bran had undergone significant changes.Through the optimization to get the grinding process of roller mill,and the crushed wheat bran was prepared into reconsitituted whole wheat flour according to national industry standard.Comparison the quality of three kinds reconsitituted whole wheat flour,drawing the following conclusions: There were significant differences in RVA among different whole wheat flours,the viscosity and setback value of the extruded whole wheat flour was significantly higher than the un-extruded whole wheat flour.The 3B-branextruded whole wheat flour(3B-E-W)had the highest water absorption and the lowest stability time;The trend of stability time of the two materials was similar to FQN,which was opposite to the degree of softening;The tensile indexes of whole wheat flour was basically consistent with the trend of farinograph indexes,the tensile properties of 3B-EW were the weakest,and the tensile indexes of common-bran-extruded whole wheat flour(CB-E-W)were higher than other whole wheat flour.From the farinose quality and extensibility of view,the characteristic of CB-E-W between the medium strength flour and weak strength flour,while the characteristic of 3B-E-W was closer to weak strength flour.There were significant increase in the number of volatile substances in whole wheat flour after extrusion,but some of the original flavor substances in wheat bran were lost or reduced,which could reduce the irritating odor in unextruded wheat bran.Steamed bun and crisp biscuits were as finished products,compared to the quality of the whole wheat flour,drawing the following conclusions: the specific volume of steamed bun of un-extruded materials was higher,and the L* value of extruded whole wheat steamed bun was lower while a *and b * value was higher than others;The sensory score of the un-extruded whole wheat steamed bun was lower than that of the extruded.There was no significant difference in the sensory score among the extruded whole wheat steamed bun.The rule of hardness and chewiness of this two kinds of material`s steamed bun were basically same,and the extrudeds were higher than the un-extrudeds,in addition,the hardness and chewiness of hammer mill`s products were the highest,and the elasticity and recovery of the extrudeds were significantly higher than un-extrudeds.The sensory score of crisp biscuits of the 3B-B-W was highest,while the CB-B-W was lowest.The crispy capacity of 3B-B-W better than others,it was more suitable for crisp biscuits.