2009_Book_FoodChemistry

15.4 Baked Products 721
(cf. 4.2.4.4.7) into volatile carbonyl compounds
in the crust. Bread aroma is enhanced, as is the
crust color, by a build-up of melanoidin compounds
from nonenzymatic browning reactions.
15.4.1.4.6 Salt
The taste of bread is rounded-off by the addition
to dough of about 1.5% NaCl. As with other
salts with small cations (e. g., sodium fumarate
or phytate), the addition of NaCl increases dough
stability. It is assumed that this is due to the
ions masking the repulsion between one charged
gluten protein molecule and another of like
charge. This allows a sufficiently close approach
of one molecule to another, thus hydrophobic and
hydrophilic interactions can occur.
15.4.1.4.7 Emulsifiers, Shortenings
Flour baking quality is positively correlated to
the content of polar lipids, particularly glycolipids
(cf. 15.2.5). Further improvements in
dough properties, baking results and end-product
freshness or shelf life (cf. 15.4.4) are gained
by adding emulsifiers to the dough, e. g., crude
lecithin (cf. 3.4.1.1), mono- and diacylglycerides
or their derivatives in which the OH-group(s) is
esterified with acetic, tartaric, lactic, monoacetyl
or diacetyl tartaric acid (cf. 3.3.2 and 8.15.3.1).
The hypotheses presented in 15.2.5 are under
discussion to explain this effect in the baking
process.
Addition of triacylglycerides (shortenings) generally
reduces the end-product volume, but there
Table 15.46. The effect of shortening on baking volume
Wheat flour
Baking volume (ml) a
Without With 3%
shortening
shortening
I 64.5 81.0
II 73.3 71.8
III b 51.6 46.3
a Baking test performed on a small scale (10 g flour).
b Flour of poor baking quality.
are exceptions depending on the wheat variety. As
illustrated by flour I in Table 15.46, addition of
3 % shortening provides a substantial increase in
baking volume. Emulsifiers are also added to the
dough to delay the aging of the crumb (cf. 15.4.4).
15.4.1.4.8 α-Amylase
Flours contain very small amounts of sugars
which are metabolizable by yeast (cf. Table
15.30). Addition of sucrose or starch syrup
at 1–2% to dough is advisable to maintain favorable
growth of yeast and therefore to provide CO 2
needed for dough leavening. Uniform leavening
over an extended time improves the quality of
many baked end-products; the crumb structure
acquires finer and more uniform porosity, while
the crust has greater elasticity.
Flours derived from wheat without sprouted
grains have some β- but very little α-amylase
activity (cf. 15.2.2.1). Thus, only a small amount
of starch is degraded to fermentable maltose by
handling dough. An insight into the extent of
starch degradation is provided by the maltose
value (cf. 15.4.1.1.1). Addition of α-amylase in
the form of malt flour or as a microbial preparation
increases the flour capacity to hydrolyze the
starch.
The activity of α-amylase as well as the levels of
maltose and glucose increase in the germination
of cereals; hence, addition of flour from malted
grains enhances the growth of yeast in dough.
However, the addition of malt to flours with weak
gluten may not be expedient because of the proteolytic
activity of the malt. α-Amylase preparations
free of proteolytic activity are available
from microorganisms (cf. 2.7.2.2.2).
Examples in Table 15.47 illustrate the effects of
α-amylse from various sources on baking quality.
While malt and fungal amylases show similar
effects, the heat-stable α-amylase from Bacillus
subtilis, with its prolonged activity even in the
oven, may be easily used to excess. Products
formed by the activities of α- andβ-amylases
are also available as reactants for nonenzymatic
browning reactions. This favorably affects the
aroma and color of the crust. α-Amylases are
added to flour not only to standardize the baking
properties, but also to delay the aging of the
crumb (cf. 15.4.4).