The influence of dietary fibres on bubble development during bread making

Dietary fibre is a common and important ingredient of a new generation of healthy food products which is experiencing rapidly increasing consumer demand. Dietary fibre increases the nutritional value of bread but usually at the same time affects rheological properties of dough and, in turn, the sensory properties of the resulting bread. The effect of fibres on bread baking performance has not been fully explored. Our investigation concerned the potential use of soluble and insoluble dietary fibres in wheat bread technology. The influence on dough rheological behavior, leavening and baking performance was studied. Doughs prepared from wheat flour containing various amounts of fibres were submitted to a lubricated squeezing test and to small amplitude oscillatory measurements. Bubble evolution during leavening and baking phases was studied by measuring the variation in time of the total volume of the sample by means of image analysis. Experimental evidence of the different behaviour of the doughs and bread, with fibres added, are presented and discussed. In general, the addition of insoluble fibres causes the dough’s strength to increase, mainly at high fibre content. By contrast, the presence of soluble fibres reduces the resistance of dough to large deformation. A negative effect of fibres on leavening is observed. The highest volume increase of the baked bread corresponds to the dough with the lowest content of fibres. The experimental evidence suggests some interesting conclusions: a) results from rheological measurements agree with those of macrostructure analysis and b) the functional role of fibres in bubble evolution depend on both the fibre source and fibre contents.