Food Chemistry

726 15 Cereals and Cereal Products

Fig. 15.41.Fermentation process for biologically leavened dough; temperature 26–32◦C (according to
Bueskens, 1978)

15.4.2.4 Fermentation

Dough passes through several stages of fermenta-
tion in the presence of growing yeast, a biological
leavening agent (Fig. 15.41). After initial fermen-
tation, the dough is divided and scaled, then the
dough pieces are rounded-off. A short fermenta-
tion is followed by sheeting and moulded dough
fermentation. The dough acquires its enlarged fi-
nal volume in the oven. The yeast produces CO 2
and ethanol which, as long as they do not dis-
solve in the aqueous phase of the dough, expand
the air bubbles (10^2 –10^5 /mm^3 ) that arise in the
dough during kneading. The volume of a square
white loaf increases 4 to 5 fold and more during
initial, intermediate, and moulded dough fermen-
tation and 5 to 7 fold during oven fermentation.
The length of time of the fermentation varies. It
depends on flour type (cf. Fig. 15.42), seasonings
incorporated, the amount of yeast and oven tem-
perature. The flour character determines the fer-

mentation tolerance, i. e. the minimum or max-
imum time after which the fermentation has to
be stopped and the dough loaded into the oven.
Dough fermentation of a weak gluten flour is
rapid, but its fermentation tolerance is low.

Fig. 15.42.The effect of fermentation time on baking
results. (rye-mix bread with two flours which differ in
baking quality;according toBueskens, 1978)

The main dough fermentation step (cf. Fig. 15.41)

can be substantially shortened by kneading the

dough energetically and/or by incorporating fast-

acting additives (for example, a mixture of bro-

mates, ascorbic acid and cysteine) into the dough.

This provides a favorable dough structure, able

to accommodate large amounts of yeast. This is

the basis for “no-time” dough making procedures,

which provide a continuous flow of dough.

In continuously operated baking processes, the

resting times required during the working of

dough (intermediate and final fermentation) are

realized in air conditioned fermentation rooms.

The resting dough forms pass through these

rooms with a defined speed.

15.4.2.5 Events Involved in Dough Making

and Dough Strengthening

15.4.2.5.1 Dough Making

Bread dough is prepared by mixing water and

flour (70:30 w/w). Water uptake, which depends

on flour type, predetermines most of the subse-

quent reactions. A high water uptake favors the

mobility of all the constituents involved in reac-

tions, e. g., enzymatic degradation of starch into

reducing sugars (Fig. 15.43).

Observation of wheat dough development by light

or scanning electron microscopy reveals that a se-

quence of forceful changes occurs in the arrange-

ment of the water-insoluble flour proteins.

When a light microscope is used to look at

a wheat flour particle under water, practically no

protein structure is discernible (Fig. 15.44,1a). If

the particle is stretched in one direction by mov-

ing the slide cover glass against the microscope

slide, numerous protein strands with inserted

starch granules become visible. These strands are