2009_Book_FoodChemistry

734 15 Cereals and Cereal Products
Table 15.52. The effect of temperature on stearyl-2-
lactylate (SSL) binding in a blend of gluten and starch a
T( ◦ C) SSL free b SSL bound b to
gluten starch
30 22.0 64 14
40 20.0 66 14
50 22.0 62 16
60 20.0 6 74
70 16.0 6 78
80 12.0 8 80
90 12.0 2 86
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 to Bloksma, 1990)
of texturizing quality of rye proteins (cf. 15.1.5).
Heating of a dough accelerates enzymatic reactions,
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 disaccharides
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.
a Blends of 17.9 g starch, 2.7 g gluten and 0.103gSSL.
b Values in % of total SSL.
Table 15.53. Specific volumes a of bread
Bread variety
ml/g
Toast bread 3.5–4.0
White bread 3.3–3.7
White mix bread b 2.5–3.0
Rye mix bread b 2.1–2.6
Rye bread 1.9–2.4
a Specific volume = volume/weight.
b cf. Table 15.63.
Table 15.54. Crumb and crust ratios in different bread
varieties
Bread variety Crumb Crust
(%) (%)
Buns, rolls (50 g) 72.5 27.5
Stick (French) white bread 68.5 31.5
White bread, pan-baked (500 g) 75.0 25.0
White bread 73.8 26.2
(self-supported dough, 500 g)
Rye mix bread 73.3 26.7
(self-supported dough, 1000 g)
Rye mix bread 84.5 15.5
(pan-baked, 1000 g)
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
produces the roasty note in the aroma profile and
the Strecker aldehydes 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