The bubble size distribution in wheat flour dough

This paper reports, for the first time, the use of non-invasive microcomputed tomography (μCT) to unambiguously determine the bubble size distribution in doughs made from strong breadmaking flour. The doughs studied were comprised of two types of dough made of two different formulae in order to yield distinct consistencies, one being a stiff dough and the other one being a slack dough. Reconstruction and three-dimensional visualization of the internal structure of the dough was accomplished at a resolution of 10 μm3 per voxel, making possible to resolve gas bubbles as small as 10 μm in diameter. Morphological characterization of the stiff and slack doughs indicated that they entrained bubbles whose size distributions were well defined by a two-parameter lognormal distribution, with geometric mean xg and geometric standard deviation σg. The bubble size distributions in the stiff and slack doughs were found to have similar geometric means, 100 and 109 μm, but quite distinct geometric standard deviation, 1.79 and 1.62, respectively. An analysis of anisotropy of bubble cross-sections (circles 10-μm thick) suggested that the small bubbles entrained in the slack dough were deformed during sample preparation to a greater extent than in the stiff dough, up to a size of 180 μm. Also, the stiff dough entrained a smaller void fraction and fewer bubbles per unit volume than did the slack dough. Furthermore, the distance between adjacent bubbles was obtained, indicating that the bubble separation distribution was normally distributed, with the stiff and slack doughs having a mean separation of 338 and 460 μm and standard deviation of 88 and 156 μm, respectively. Overall, this paper shows how the bubble size distribution in dough can be determined using X-ray microcomputed tomography, opening the possibility to gaining a more comprehensive insight into the aeration phenomenon in wheat flour dough.