Proofing
Thawed dough pieces should be left to proof before
baking, just like the fresh ones, either for a certain period
of time or until they obtain the desirable volume.
Proofing is mainly attributed to the action of yeast which contributes to many changes that are collectively
termed dough maturing or ripening. Properly matured
dough exhibits optimum rheological properties (optimum
balance of extensibility and elasticity) as well as
good machinability and produces bread with desirable
volume and crumb characteristics. During dough
maturing several reactions occur. As yeast is fermented
alcohol and carbon dioxide are produced among other
products. Because alcohol is water-miscible and since
appreciable amounts are formed, it influences the colloidal
nature of the flour proteins and alters the interfacial
tension within the dough. Additionally, carbon
dioxide partly dissolves in the aqueous phase of the
dough and forms weakly ionizable carbonic acid, which
lowers the pH of the system. Carbon dioxide production
also contributes to dough distension (Beuchat, 1987).
Growth of gas cells depends in part on cell size. Greater
pressure is needed to expand a small gas cell than a larger
one, and it is possible that the smallest bubbles will
not expand at all. Gas cells stabilization and gas retention
are of considerable interest as they fairly determine
crumb structure and volume of wheat bread. In the case
of frozen fermented doughs, gas cell structure
significantly affects frozen storage stability. A dough
that contains a large number of small bubbles with a
narrow size distribution and thick walls will be more
stable than a dough that contains bubbles with less
uniform size distribution and thin walls surrounding the
larger bubbles (Autio & Laurikainen, 1997). Proof time
for frozen-thawed dough is necessarily longer than that
for conventional dough (Table 2). This is due to the
lower dough temperature at which thawed pieces reach
the proof box, and to a certain loss of dough gas retention
power and yeast activity caused by the freezing process