Part-Baked Products - Minimally Processed Foods - page 149

Evaporation-condensation will continue until the temperature of the whole
crumb has achieved 100 °C (Wagner et al. 2007 ; Purlis and Salvadori 2009 ). During
baking, the internal temperature of the dough reaches up to 100 °C, and three impor-
tant changes take place in the dough properties. These are dough expansion (volume
increase to 4-5-fold of its initial volume), a predominantly elastic crumb, and inter-
connected cell formation (Singh and Bhattacharya 2005 ). The early stages of baking
plays a signifi cant role in determining the resultant loaf volume and bread quality
(Fan et al. 1999 ). In the initial stages of baking, dough forms a bubbly structure with
an almost uniform density. The material surrounding the bubbles is initially liquid.
In the later stages of baking, material properties of the matrix changes, and rela-
tively negligible changes occurs at the end of the baking process. As the tempera-
ture inside the dough increases, the pressure inside the bubbles rises due to the water
evaporating and therefore the dough expands (Jefferson et al. 2007 ).
One of the objectives of baking is to obtain a particular colour on the surface of
baked products. The surface colour, texture and aroma play a signifi cant role in
producing quality baked products. For this reason, surface colour may be consid-
ered a critical index of baking (Zanoni et al. 1995a ). During baking, the water con-
tent of crust decreases and the temperature of the surface can exceed 100 °C and
Maillard and caramelization reactions develop colour and desired fl avours (Vanina
et al. 2009 ). The surface colour is also called as surface browning (i.e. yellow-gold
colour formation) (Fig. 8.2 ). Since browning can be easily monitored during the
baking process by in-line sensors, it is can be used as a control parameter to observe
the extend of process (Purlis and Salvadori 2007 ; Purlis 2010a , b ). Figure 8.3 shows
the formation of browning (i.e. crust colour) at an oven temperature of 250 °C.
Another factor that determines the baking time is starch gelatinization during
baking. Many starch granules may remain intact and their irregular shape depends
Fig. 8.2 Surface color of bread baked at different time and temperature (Purlis 2010b )