Study On Chemical Composition Variation Of Wheat Flour Particles With Different Size And Its Effect On Flour Quality And It's Regulation

Particle size is one of the important parameters that affect the quality of wheat flour.During the process of milling,wheat grains will be splited in different ways under different processing processes(grinding process and tempering pattern),which lead to the changes in particle size and chemical composition distribution of wheat flour particles,thereby affecting the quality of wheat flour.In the present study,through investgating the wheat flour particles size distribution,bulk chemical composition,surface chemical composition of wheat flour particle with different sizes and the relationship with the quality of wheat flour,the variation regulation of chemical composition and surface chemical composition of wheat flour particle with different sizes and the correlation between them were revealed.The quality changes caused by the change of particle size distribution and chemical composition of flour particles were explained from the molecular point.Ultimately,the quality of flour was regulated by the change of conditioning and grinding methods.This project has important value and guiding significance for deeply understanding the structure of wheat endosperm,explaining the quality difference of wheat flour with different particle size,guiding the flour recombination in wheat processing,adjusting the flour quality and so on.In order to explore the distribution rule of the bulk chemical composition and surface chemical composition of flour particle with different sizes,the microstructure and chemical composition characteristics of flour particle with different sizes obtained under the same grinding conditions were examined and the correlation between the bulk chemical composition and surface chemical composition of wheat flour was analyzed.The results of microstructure and chemical composition analysis both showed that the particle structure,protein composition and starch composition of flour particle with different sizes were significantly different.The content of gluten protein was higher in the fine particle,indicating that the large and medium flour particle might be from inner layer or central endosperm of wheat.Amino acid analysis showed that the distribution of glutamate in flour particle with different sizes was contrary to most amino acids.While X-ray photoelectron spectroscopy(XPS)analysis showed that the surface composition of flour particle with different sizes was significantly different and had no correlation with bulk chemical composition.The particle size distribution of wheat flour will effect wheat flour quality.The gluten quality characteristics,dough rheological properties,dough fermentation characteristics,dough microstructure and steamed bread quality characteristics of wheat flour with different particle sizes under the same grinding condition was analyzed,and the contribution of wheat flour with different particle sizes to steamed bread quality was studied by item deficiency particle size method.The results showed that the wet gluten content,gluten index,formation time,stability time,powder quality index and the viscosity of dough of the large and medium particles were higher than those of fine particle.The medium flour particle had more sulfhydryl groups,and the network structure of dough was clear and dense,and the continuity of gluten network was better.Furthermore,the disulfide bond,weakening degree,gelatinization temperature,and the color of steamed bread of medium particle flour was higher than that of large particle flour.After fermentation for 40 minutes,the hardness of medium particle flour dough had greater decrease than that of large and fine particle flour;the hardness,stickiness and chewability of steamed bread with medium particle flour was significantly lower than that of large and fine particle flour,while the recovery of steamed bread with medium particle flour was higher than that of steamed bread with large and fine particle.Wheat flour with particle sizes of38?48 ?m,25?38 ?m and 104?112 ?m had the greatest influence on the adhesion,recovery and cohesion;hardness,chewing degree and stickiness;and elasticity of steamed bread,respectively.In order to investigate the effect of tempering pattern on particle sizes distribution and quality characteristics of flour,the particle sizes distribution,chemical composition,dough and steamed bread quality of wheat flour under different tempering conditions was analyzed.The results showed that the content of wheat flour with fine particle increased with the increasing of water content,while wheat flour with large particles decreased;the content of dissolved protein had no obvious change,but the total protein content and the ratio of amylopectin to amylopectin decreased.When the addition amount of water was15.5%,the dough had greatest hardness and the smallest adhesion;the steamed bread had the smallest adhesion and recovery.The cohesion,adhesive and chewiness of steamed bread were the smallest when the amount of water added was 16.5%.With the increase of conditioning temperature,the content of fine particle in wheat flour decreased,while the content of large particles increased;the content of glutelin,stability time and tensile resistance was higher at 35?,while the ratio of amylopectin to amylopectin and weakening degree were lower at 35?;wheat flour had the highest gelatinization viscosity and the dough had the smallest hardness at 45?.Under vacuum conditioning,the proportion of fine particle was higher than large particle.The contents of albumin,gliadin,globulin,total protein,damaged starch and the ratio of amylopectin to amylopectin in wheat flour under vacuum tempering were lower than those of conventional conditioning,while the glutelin content was higher than that of conventional conditioning.The gelatinization viscosity,dough formation time,weakening degree and cohesion of steamed bread were larger than those of conventional conditioning,while tensile resistance,dough hardness,viscidity and chewability of steamed bread were lower than those of conventional conditioning.In order to investigate the effect of grinding process on the particle sizes distribution and chemical composition of wheat flour,the change of particle size distribution and the difference of composition of wheat flour under different grinding conditions were analyzed.The results showed that the particle sizes of wheat flour was mainly distributed in the range of 95 ?m?112 ?m,and under A grinding process,the amount was higher than that under B process,while the distribution of flour in other particle size range under B grinding process was slightly more than that under A process.The content of total starch in wheat flour with different particle sizes under A grinding process was higher than that under B grinding process,and the content of damaged starch and protein was lower than that under B grinding condition.The distribution of total protein,albumin,globulin and glutelin was more in large particle flour,and the glutamine content under B grinding condition was higher than that under A grinding condition.Gliadin was mainly distributed in wheat flour with particle sizes ranging from 95um?112um.The distribution of chemical composition on the surface of wheat flour particles was different with the change of grinding conditions.