Food Chemistry

734 15 Cereals and Cereal Products

Fig. 15.47.Viscosity (η,—) and tensile stress
(δ,◦—◦) of a wheat dough as well as pressure (p,•—•)
in the gas bubbles as a function of temperature during
the baking process (according toBloksma, 1990)

of texturizing quality of rye proteins (cf. 15.1.5).
Heating of a dough accelerates enzymatic re-
actions, e. g., starch degradation (cf. 15.4.2.4).
Above the “temperature optimum” (cf. 2.5.4.3)
the reactions are inhibited by denaturation of the
enzymes.
The vitamins of the B group are lost to different
extents during baking. In white bread, the losses
amount to 20% (flour type 550)−50% (flour
type 1150) of thiamine, 6–14% of riboflavin and
0–15% of pyridoxine.
Starch degrades to dextrins, mono- and disac-
charides at the relatively high temperatures to
which the outer part of the dough is exposed.
Caramelization and nonenzymatic browning
reactions also occur, providing the sweetness
and color of the crust. The thickness of the
crust is dependent on temperature and baking
time (Table 15.51) and type of baked product
(Table 15.54). The composition of some types of
bread is presented in Table 15.55.

15.4.3.3 Aroma

15.4.3.3.1 White Bread Crust

The substances which produce the aroma
profile of a loaf of French bread (baguette)
(Table 15.56) originate from the crust. They
are listed in Table 15.57. 2-Acetyl-1-pyrroline

Table 15.52.The effect of temperature on stearyl-2-

lactylate (SSL) binding in a blend of gluten and starcha

T(◦C) SSL freeb SSL boundbto

gluten starch

30 22. 06414

40 20. 06614

50 22. 06216

60 20. 0674

70 16. 0678

80 12. 0880

90 12. 0286

aBlends of 17.9 g starch, 2.7 g gluten and 0.103gSSL.

bValues in % of total SSL.

Table 15.53.Specific volumesaof bread

Bread variety ml/g

Toast bread 3 .5–4. 0

White bread 3 .3–3. 7

White mix breadb 2 .5–3. 0

Rye mix breadb 2 .1–2. 6

Rye bread 1 .9–2. 4

aSpecific volume=volume/weight.

bcf. Table 15.63.

Table 15.54.Crumb and crust ratios in different bread

varieties

Bread variety Crumb Crust

(%) (%)

Buns, rolls (50 g) 72. 527. 5

Stick (French) white bread 68. 531. 5

White bread, pan-baked (500 g) 75. 025. 0

White bread 73. 826. 2

(self-supported dough, 500 g)

Rye mix bread 73. 326. 7

(self-supported dough, 1000 g)

Rye mix bread 84. 515. 5

(pan-baked, 1000 g)

produces the roasty note in the aroma profile and

theStreckeraldehydes methylpropanal, 2- and 3-

methylbutanal the malty note. The compounds

(E)-2-nonenal and 1-octen-3-one are primarily

responsible for the fatty impression.

The aroma of a baguette is not stable. Even

four hours after the bread has left the oven, the

intensities of the malty and sweet notes in the