| This acticle taked the ultramicro bran(average particle size of 40 μm) as raw material,Compared with coarse bran(average particle size of 349 μm) and medium size bran(average particle size of 138 μm) on the aspect of the dissolution characteristics of flavonoids, the ability of cation exchange, the removal of harmful ions and the antioxidant activity of flavonoids. Substituted the three distinct particle sizes of the wheat bran with six ratios which contained 0%, 5%, 10%, 5%, 20% and 25% 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 flour products and flavor characteristics and sensory evaluation. In addition, preliminary study on the retrogradation effect of ultramicro bran steamed buns. Give the result as follows.The functional properties of ultrafine bran were changed. Compared with coarse bran and medium size bran, The water retention capability in ultramicro bran was decreased with 0.32g/g and 0.5g/g respectively, the oil holding capacity was decreased with 0.34g/g and 0.61g/g respectively;the water swilling capacity was decreased with 0.35 m L/g and 0.79 m L/g respectively, the flavonoids content in ultramicro bran extract was increased with 0.77‰ and 0.39‰ respectively, When the adsorption time reached 1.5 hours, the NO2—scavenging rate of ultramicro bran was increased by 10.18% and 5.29% respectively, the ability of adsorbing Pb2+,Cd2+,Hg2+ was rised by 30.1% and 24.9%, 31.6% and 12.7%, 9.6% and 15.2% respectively. When the adsorption time reached 1.5 hours, the adsorption capacity of ultramicro bran on bile sodium decreased 3.27 mg/g and 1.21 mg/g respectively. The cation exchange capacity decreased slightly.With the increasing of wheat bran which increased dough water absorption and the time of formation begins to decrease and then increases, stable time showed a downward trend, and the stable time decreased slowly as measuring by farinograph. At the same time, extension area was raised initially and then reduced, decreased extensibility, and increased maximum resistance initially and then reduced as measuring by extensograph. And when the content of bran is less, ultramicro bran showed advantages. The observation to dough microscopic structure from scanning electron microscope showed that the substitution level of 10% of ultramicro bran dough, its internal structure is relatively uniform and dense, but the substitution level of 25% of ultramicro bran dough, it can be fully filled in the gluten protein matrix. The extension of the whole network structure is changed by the dietary fiber swelling, solid degree increased, it lead to the steamed bread specific volume has shrunk. And when the content of bran is more, ultramicro bran showed disadvantages to dough obviously.Supplementing wheat bran to flour which makes the quality of steamed buns and bread has a different degree of decline. Although medium size bran than superfine bran and coarse bran is more suitable for flour production, but ultramicro bran in functional properties has more advantages, the nutrients are more conducive to the body’s absorption and utilization. Combine with the rheological properties, texture characteristics, sensory evaluation and nutritional properties of dough, the final assessment of the substitution level of 10% of ultramicro bran had good influence on steam buns and bread relatively.The flavor compounds of bran steamed buns were studied, the result showed that the total amount of flavor were increased and kinds of flavor substances increased after bran was added, such as alcohols, esters, ect. The increase of the material helps to form bran steamed buns special flavor. Superfine bran due to more small particles, cell wall broken more completely, physical contact with the yeast more fully, so bran would produced more and more type and quantity of flavor compounds in the process of fermentation and steaming, but it also have difference between different particle size of wheat bran.The experiment through the TPA, DSC, NMR method were used to disscuss the bran steamed buns retrogradation mechanism preliminary, the results showed that superfine bran to add plays a positive role on steamed buns abate retrogradation. In the process of aging, adding bran makes the hardness of steamed bread becomes larger, the elasticity and the recovery is reduced. In the late aging bran steamed buns quality and structure characteristics of changing trend lower than the blank group, the enthalpy value of the substitution level of 10% of ultramicro bran steamed buns is relatively smaller, indicates that the retrogradation degree is small. NMR results showed that bran contains a large number of non-starch polysaccharides, their strong water absorption effect of bran steamed buns have affected T2 relaxation time and T2 peak area. With aging time becomes longer, T2 relaxation time and proton density A2 are reduced. Bran steamed buns A21 is bigger than blank group, but A22 is smaller. For bran steamed buns, the peak area was negatively correlated with bran particle size and T21, and the peak area of T22 is positively related. |
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