1998

Räsänen, Janne

The baking properties of prefermented frozen doughs were examined with frozen storage times up to 14 days at -20°C. Different types of flour, prefermentation times, water contents, and hydrocolloids were investigated. The factors used to explain the observed improvements were yeasted dough rheology, pore structure, and water state. The deterioration in loaf properties was observed to fall into two categories: those due to freezing and subsequent thawing (freeze-thaw stability), and those occurring over longer frozen storages (frozen storage stability). Shorter prefermentation time (25 vs. 40 min) improved the freeze-thaw stability of frozen doughs and increased the loaf volumes on average by 20%. In the same way the baking properties became more independent of flour quality, and extra-strong flours were not needed to achieve loaf volumes similar to those of fresh baking. In the pore structure studies, shorter prefermentation time was observed to change the structure for more even. Smaller air bubbles with thicker cell walls were not so sensitive to ice crystal damage. Shorter prefermentation time did not significantly improve the frozen storage stability of prefermented frozen doughs. The major decrease in loaf volumes during frozen storage occurred during the first week, after which there was little change. For the achievement of fresh-like loaf properties after 14 days frozen storage, lower water contents were needed (2 per-centage units reduction from the fresh baking optimum). The role of water became clear in the analyses of water state in frozen doughs. The self-diffusion coefficient and the amount of liquid phase increased during frozen storage because of ice crystal growth, but the increase could be minimized by reducing the water content and adding hydrocolloids. Thus, the major deteriorations in prefermented frozen doughs are caused by ice crystals. When shorter prefermentation time was combined with reduced water content, yeasted dough rheology after frozen storage was similar to that of fresh dough.