Studies On Effects Of Bran Particle Size On Chinese Steamed Bread Quality

Wheat bran were passed through different grinders to process into four distinct particle sizes including as coarse, medium, fine and minute. Substituted them with four ratios which contained 0%,10%,20% and 30% for wheat flour respectively to do the research in order to investigate the effects of bran particle size on rheological properties of dough and quality of steamed bread, and finally to obtain the appropriate particle size and ratio in steamed bread with bran. The affecting mechanism was discussed, the rational adding amounts of bran and additives were determined, and the optimum formulations for improving quality of steamed bread with bran were develped.The decreasing of bran particle size which added into steamed bread dough systems, increased dough water absorption slowly and raised weakness, reduced initially and then raised development time, and had big change on stable time as measuring by farinograph. And at the same time, decreased extensibility, reduced maximum resistance initially and then increased, and generally increased energy as measuring by extensograph. Dough water absorption rate, development time and weakness increased with the raising of substitution level, while stable time decreased. Extensibility dropped, maximum resistance decreased first and then raised, and energy reduced with the increasing ratios of bran. Dough containing fine and minute particle size bran exhibited more strength than dough containing coarse and medium bran as measuring by the extensograph.The steaming experiment showed that the volume and specific volume reduced with the decreasing of bran particle size, while they also deteriorated as the bran substitution level increased, so did the quality of steamed bread. But the sensory evaluation demonstrated that dough containing medium and fine particle size bran had higher appearance scores than the ones with coarse and minute bran. The ones with coarse and minute particle size bran gained lower inner structure scores than the ones with medium and fine bran, and they were difficult to accept for customers. Smaller particle size bran had better appearance which was smoother and had better mouth feeling, but it would have bitter taste when the particle size of bran was too small. The specific volume, appearance scores, inner structure scores and total scores of steamed bread with bran all decreased significantly with the increasing of bran substional ratio. So, the medium particle size and substitution level of 20% of bran was the best for customers by evaluating it's nutrition, acceptance and processing properties.The objective of improving the quality of wheat bran which had medium particle size and substitution level of 20% incorporated with steamed bread, one-factor and orthogonal experiments were conducted and we gained the best scheme as follows:3% gluten,0.15% CSL-SSL,15 mg/kg xylanase and 4mg/kg lypase. They improved the specific volume and sensory evaluation score of steamed bread with bran 0.53mL/g and 17.8 scores, respectively.In the system of wheat flour with bran, pericarp particles were part of the problem which provided little coherent and continuous dough structure from the observation to dough microscopic structure from scanning electron microscope. Gum materials facilitated stringing of small starch granules and their adherence to large granules. And starch containing in flour with bran was more important than the one in basic flour. Dough with bran had less capacity of expanding starch than basic flour dough system and it also had lower fermenting property. Additing improver could not only modify the quality of dough with bran, but also improve the character of steamed bread with bran.