2009_Book_FoodChemistry

15.4 Baked Products 725
participate in Maillard reactions during baking,
providing the more intense aroma.
15.4.2.3 Kneading
The kneading process is characterized by the following
stages: mixing of the ingredients and seasonings;
dough development and dough plastification.
The energy input into dough kneading, the dough
properties and baking volumes are interrelated.
For each dough the baking volume passes through
an optimum which is dependent on kneading energy
input (Fig. 15.40). This optimum shifts towards
lower energy input with a flour of weak
gluten content and towards higher energy input
with flours of strong gluten content; and, as expected,
the position of the optimum can be influenced
by flour improvers. Increased additions,
especially of azodicarbonamide, to the dough result
in a successive drop in kneading energy input
(Fig. 15.40).
As the kneading energy moves away from the optimum,
the dough becomes wetter, it starts to stick
to trough walls and its gasholding ability drops
(cf. 15.4.2.5 and Fig. 15.44, 14 and 56). Dough
development of wheat flours requires close to
double the kneading time of rye flours.
The machines used for kneading are grouped according
to their performance based on kneading
time: fast, intensive, and high power kneaders and
mixers (Table 15.49). However, the groups are
not sharply divided. As the kneading speed increases,
the temperature of the dough rises (Table
15.49). Hence, cooling must be used during
kneading to keep the temperature at 22–30 ◦ Cor,
with high speed mixers, at 26–33 ◦ C. The mixer,
in a true sense, does not knead the dough, but rips
or ruptures it. This could reduce the stability of
the dough to such an extent that it could be baked
only as panbread (in which case the pan walls
support the dough) but not as bread made from
selfsupporting dough.
Table 15.49. Examples for kneading conditions in
white bread dough making
Dough mixer/ Speed Kneading Dough
kneader (rpm) time heat a
(min) ΔT( ◦ C)
Rapid kneader 60–75 20 2
Intensive kneader 120–180 10 5
High power
kneader 450 3–5
Mixer 1440 1 9
Mixer 2900 0.75 14
Fig. 15.40. Bread volume as affected by kneading energy
input (according to Frazier et al., 1979)
a Temperature rise during kneading time.