Bubble growth and collapse in pre-fermented doughs during freezing, thawing and final proving

The formation of large bubbles was observed by MRI during freezing. This was attributed to the compression of gases in a structure that cannot globally deform (due to the frozen shell), the consecutive rupture of dough films and the coalescence of neighbouring bubbles. The fraction occupied by these large bubbles was consistent with the hypothesis of thermal contraction, though this was not the only mechanism in play. Conversely medium-sized bubbles initially present in the dough did not grow during freezing, suggesting that maximum stress was dependent on location. These large bubbles were suspected to contribute greatly to dough collapse just after thawing since they were still present in the thawed dough, but in an elongated form. Collapse was related to delayed expansion during the second fermentation stage. The longer the duration of the first fermentation stage, the more collapsed the dough structure became just after thawing and the coarser the dough structure was at the end of the second fermentation period. (C) 2010 Elsevier Ltd. All rights reserved.