Effects of glycerol and moisture redistribution on mechanical properties of white bread

Effects of glycerol and moisture redistribution on mechanical properties of bread were investigated. Firmness increased in all bread crumb over storage time but firming rate was dependent on the initial moisture content, storage method (stored with and without crust), and the presence of glycerol. Faster firming was observed when bread crumb had low initial moisture content and high glycerol level, and was stored with crust. The effect of glycerol was more pronounced when stored with crust, suggesting a critical role of water loss. Firmness showed a good correlation (r(2)=0.95) with the scale factor (C-1) from a mathematical model. Recoverable work rapidly decreased in first three days of storage and then remained relatively unchanged thereafter. Hardening of aged bread (but not fresh bread) by glycerol may be explained by local dehydration of bread polymer due to osmotic dehydration or competition for water, which in turn promote more rapid amorphous network formation but less amylopectin recrystallization.