Biomedical Engineering Reference
In-Depth Information
Fig. 8.3
Browning profi le of
bread baked at 250 °C
(Zanoni et al.
1995a
)
on the available water and temperature of baking (Aissa et al.
2010
). A complete
starch gelatinization in the crumb should be considered the fi rst quality index of soft
baked products, such as breads and cakes. If starch gelatinization does not occur
during the baking, the quality (i.e. texture and appearance) of the product cannot be
ensured. For this reason, the degree of gelatinization is also used as a baking index
(Zanoni et al.
1995b
).
8.3
Staling of Baked Products
Bakery products during storage are subjected to several changes and affect the qual-
ity of the products ranging from staling to total spoilage. The shelf life of these
products is defi ned as the time when quality losses do not exceed a tolerated level
and it can be decisively infl uenced by its storage conditions (Karao
lu et al.
2008
).
Bread and similar baked products have a limited shelf life. Physicochemical
changes such as staling, textural changes, and microbiological spoilage (i.e. yeast,
mould, bacterial growth) shortens the shelf life. Staling is defi ned as “almost any
change, sort of microbiological spoilage, that occurs in bread or other products, dur-
ing the post baking period, making it less acceptable to the consumer” (Smith et al.
2004
). For this reason, considerable attention has been focused in controlling the
staling of baked products (Bechtel
1953
; Karao
ğ
lu and Kotancılar
2006
).
Staling involves the softening of the crust and the hardening of the crumb. The
softening of the crust is a consequence of the migration of water from the crumb to
the crust. However, the hardening of the crumb is more responsible for staling and
it is a complex phenomenon where multiple mechanisms are involved (Ronda
et al.
2011
). The staling is a process of chemical and physical changes such as
moisture redistribution, drying, starch retrogradation, increased fi rmness as well as
loss of aroma and fl avour (Karao
ğ
lu et al.
2008
). Cereal fl our constituent of bakery
products, contains carbohydrates, proteins and lipids or fats. Since starch is the
ğ
