Investigating effects of bran particle size on dough rheology using a modelling approach based on the Chopin Mixolab

This work extends the Mixolab modelling approach for understanding arabinoxylan fibre effects in breadmaking to conventional fibres, psyllium and wheat bran, used at higher levels, and applies the approach to investigate the effects of bran particle size on Mixolab parameters. The approach allows effects of flour removal, fibre replacement and water adjustment on Mixolab parameters to be distinguished. Psyllium was replaced for flour at levels of 2, 4 and 6%, and Coarse, Medium and Fine wheat bran at levels of 5, 10 and 15%. Linear models were adequate to describe flour, fibre and water effects over these wide ranges of substitution. Psyllium had larger effects than wheat bran on Mixolab parameters; psyllium absorbed 2.7 times its own weight in water, and increased water absorption by 2% at 1% replacement, while bran absorbed around its own weight in water and increased water absorption by about 0.37% at 1% replacement. Bran particle size had only small effects on Mixolab parameters, in agreement with most previous workers, with suggestions of consistent patterns of effects on C2 and C4, which may relate to how bran particle size affects rates of water release from bran during heating. It is concluded that bran particle size effects in bread predominantly arise during the rapid expansion that occurs during proving and baking, which is not mimicked by the Mixolab. Extending the modelling approach to data from instruments that measure dough expansion and from baking trials could give more precise understanding of the mechanisms of fibre effects in breadmaking.