Effects of wheat bran particle size on rheological properties of whole-wheat dough

In the study,wheat bran was ground by superfine grinding with various strengths,and then added into straight grade flour according to flour extraction rate( 70%) to obtain whole- wheat flour( WWF).The average particle sizes of four wheat bran after superfine grinding were 327,209,144,45 μm,respectively. The influences of wheat bran particle size on the rheological properties of whole- wheat dough( WWD) were investigated.The analysis of viscosity showed that the peak viscosity,trough,final viscosity and setback of WWF were significantly increased as wheat bran particle size reduced. The farinograph analysis indicated that as the wheat bran particle size reduced,the water absorption of WWF was remarkably increased,but the stability time was decreased and the softening degree was enhanced.Extensograph analysis showed that fermentation time could affect the effects of wheat bran particle size on the dough gluten network structure; in the stages of extension and formation of gluten network( 45~90,90~135 min),smaller wheat bran particle size could promote the compactness of gluten network but reduced the extensibility. Oscillatory rheological properties analysis indicated that as wheat bran particle size decreased,the elastic modulus and viscous modulus of WWD showed a downward trend,but still higher than the control group within the scanning range of frequency.Based on the obtained results,it can be speculated that the decreased wheat bran particle size promoted the separation between starch granules and bran layer and facilitated the distribution of wheat bran fiber,but caused more steric hindrance during the development of gluten network and inhibited the binding between the protein molecules and the interactions of gluten matrix with starch granules.