Relationship between firming and water mobility in starch-based food systems during storage

Magnetic resonance imaging (MRI) and pulsed nuclear magnetic resonance techniques were used to study the water mobility in sweet rolls during storage. Different fractions of water with distinguishable molecular mobility were identified. MRI provided information on the spatial distribution of water content and of water mobility. During storage, moisture migrated from the crumb to the crust, which was associated with the firming of the crumb. A spatial redistribution of water mobility within the sample was also observed. As storage time increased, the mobility of the less mobile water fraction decreased; whereas the mobility of the more mobile water fraction increased upon staling, suggesting a redistribution of water mobility within the water molecules in the samples. A relationship between water mobility and staling was discussed.