Moisture redistribution and phase transitions during bread staling

Standard white breads were stored with or without crust at 25 degrees C in hermetic pouches. During two weeks of storage, the crumb moisture content a nd water activity (a(w)) decreased significantly when stored with crust. Wh en stored without crust, moisture content and a(w) remained relatively unch anged The causes of the initial fuming of both breads over zero to seven da ys were not conclusive. But when stored beyond seven days, bread stared wit h crust was significantly firmer in texture and higher in amylopectin recry stallization than bread stored without crust. Moisture redistribution from crumb to crust played a significant role. This was accompanied by a decreas e in freezable water in the bread crumb stored with crust. This loss in fre ezable water coincided with changes in the thermomechanical profile only in the case of sample stored with crust intact (and with a significant total and freezable water loss). Bread crumb stored without crust did not change in total and freezable water and showed less change in thermomechanical tra nsitions. The transition occurring at approximate to 60 degrees C (T-2) cor related with amylopectin recrystallization but it could also have been caus ed by moisture loss during the analysis. Moisture migration from crumb to c rust greatly reduced the total and freezable water in the crumb region resu lting in a significant reduction in the magnitude of the mechanical transit ion at approximate to 0 degrees C (T-1) as well as an increase in the stora ge modulus.