2009_Book_FoodChemistry

712 15 Cereals and Cereal Products
Table 15.40. Concentration of SH- and SS-groups in
flour of different wheat cultivars
Cultivar SH SS SS/SH
µmole per g flour
Kolibri 1.15 12.5 10.9
Caribo topfit 0.88 12.2 13.9
Strong Canadian wheats 0.95 13.4 14.1
Inland wheat I a 0.75 10.2 13.6
Inland II a 1.05 12.6 12.0
Canadian Western Red Spring
Wheat (CWRS) 1.26 12.9 10.2
a Marketed flour blendings.
cultivar, Table 15.41). Gluten swelling power
is assessed by a sedimentation value as recommended
by Zeleny. In this test, flour is suspended
in an aliquot of a mixture of lactic acid (3.8g),
isopropanol (200 ml) and water (800 ml). The
higher the volume of the sedimented gluten and
starch, the better should be the baking quality of
the flour.
For a given wheat cultivar, grown under similar
climatic and soil conditions, the baking volume
correlates with the protein content of the flour
(Fig. 15.24). A similar linear relationship is not
readily attainable for flours from different cultivars,
as evidenced by the very different slopes of
the regression lines.
The parameters involved here are those described
in Section 15.2.1.4 as responsible for the properties
of gluten. These include type, amount,
and degree of polymerization of the HMW and
LMW subunits of glutenin as well as the ratio
gliadin/glutenin.
On the whole, the structure of wheat gluten
has been so far evaluated to be able to describe
variety-specific differences in the technological
properties.
Wheat cultivars differ in the content of their thiol
and disulfide groups (Table 15.40). This implies
that the stability of a dough may be strongly
influenced by a SH/SS exchange between a low
molecular weight SH-peptide and gluten proteins.
This also implies that a positive correlation
Table 15.41. Baking quality data of some wheat flours
Wheat cultivar a
Monopol Nimbus Maris
Huntsman
Protein (% dry matter) b 13.2 11.6 11.8
Wet gluten (%) 35.1 24.7 34.3
Farinogram c
Water absorption (%) 59.2 54.8 59.8
Dough development time (min) 5.0 1.0 2.0
Dough stability (min) 5.0 1.5 0.5
Mixing Tolerance Index d (FU) 30 80 130
Extensogram e
Area (dough strength, cm 2 ) 143 75 17
Resistance of the dough to extension (EU) 700 680 110
Extensibility (mm) 170 92 100
Baking test
Dough surface somewhat wet to normal normal wet, gluey
Dough elasticity normal somewhat short weak
Baking volume (ml) 738 630 510
a Wheat cultivars with breadmaking quality corresponding to very good (“Monopol”), average (“Nimbus”) and
poor (“Maris Huntsman”).
b Factor N × 5.7.
c Explanation in Fig. 15.26; dough consistency: 500 FU.
d Measured after 10 min in Farinogram units (FU).
e Explanation in Fig. 15.29.