2009_Book_FoodChemistry

714 15 Cereals and Cereal Products
ious indices have been defined (cf. Fig. 15.26);
usually they refer to doughs with a maximum
consistency of 500 FU.
Flours with strong gluten absorb more water
and show longer dough development and stability
times than do flours with weak gluten
(Table 15.41). Corresponding results are obtained
with the Swanson and Working mixographs.
A standardized piece of dough is stretched with
the hook of a Brabender extensograph until the
piece breaks (Fig. 15.27). As shown in Fig. 15.29,
a graph of force (resistance to extension) versus
stretching distance (extensibility) provides information
about the stability of a dough, its gasholding
capacity and fermentation tolerance. Of the
examples given in Table 15.41, the “Monopol”
cultivar obviously has strong gluten. The “Nimbus”
cultivar has short gluten, as reflected by its
low extensibility. The “Maris Huntsman” cultivar
has a very weak gluten, as shown by the low resistance
of its dough to extension and also by its
low extensibility, and very small extension area.
Similar results are obtained with the Chopin extensograph
or alveograph used widely in France.
A piece of dough mounted on a perforated plate
is blown into a ball. The pressure in the ball of
dough is plotted against the time (cf. Fig. 15.28).
In contrast to the Brabender extensograph, the
dough is extended in two dimensions. As in the
extensogram, the resistance of the dough to extension
and its extensibility are obtained from the
maximal height and width of the alveogram.
Fig. 15.27. Extensograph (according to Rohrlich and
Thomas, 1967). The cylindrical piece of dough (1) is
fixed by dough clamps (3) and placed on the balance
fork (2). Themotor(4) of the stretching unit (5) is
then started. The arm moves downward into the dough
and extends it at constant speed. Simultaneously, the
forces opposing the stretching action are transmitted
through the lever system (6) to the balance system (7).
This is coupled to a recording arm of the strip chart
recorder (8). The fork of the balance system is coupled
to an oil damper (9) to reduce the recoil
Fig. 15.28. Alveogram (cf. text)
Fig. 15.26. Farinogram. The following data are pertinent
for quality assessment of flour: A dough development
time, B dough stability (dough consistency does
not change), C decrease in dough consistency after
a given time, here 12 min. FU: farinogram units
15.4.1.1.3 Baking Tests
Direct information about the baking quality
of a flour is obtained from baking tests under
standardized conditions. Baking volume (cf. Ta-