Fermentation time and fiber effects on recrystallization of starch components and staling of bread from frozen part-baked bread

Staling of white wheat bread produced from frozen part-baked bread (PBB) of different fermentation times (90-120-420 min) and fiber contents (6% wheat bran and 6% wheat bran +2% inulin) was studied. Volume, texture, crumb and crust water content, water activity and crumb thermal properties (including Tm′ and Tg′) were measured after thawing and final baking. The results confirmed that typical freezing temperatures may not ensure the glassy state of the unfrozen phase of PBB, which may accelerate staling of final breads. The evolution of starch retrogradation, quantified by DSC, and of the crust and crumb water contents were analysed and related to the aging of bread. Firmness and cohesiveness values were used to quantify the extent of staling. Avrami equation was fitted to staling data with R2 coefficients above 0.9 in all cases. Bread characteristics and staling kinetics were significantly affected by fermentation time and fiber, particularly inulin. Inulin promoted amylopectin recrystallization and delayed the water movement from crumb to crust during staling. The combined effects of recrystallization and water loss in the starch fraction explained firming and cohesiveness loss kinetics.