2009_Book_FoodChemistry

15.4 Baked Products 713
of the maltose value (diastatic activity). This is
a quantitative determination of reducing sugars
prior to and after incubation of a flour suspension
at 27 ◦ C for 1 h. Flours with a maltose content
of <1.0% are regarded as weak fermentation
promoters; values above 2.5% are flours from
sprouted kernels. They provide poor baking quality.
15.4.1.1.2 Physical Assays
Fig. 15.24. Examples of relationship between protein
content of flour and bread volume (according to
Pomeranz, 1977). United States winter wheat cultivars:
1 Chiefkan, 2 Blackhull, 3 Nebred. The regression lines
are based on numerous sample analyses
The instruments widely used in practice for
the determination of the rheological properties
of dough can be divided into recording dough
kneaders and tensile testers. Dough development
is followed with a Brabender farinograph
(Fig. 15.25), with which measurement is made
of the volume of water absorbed by the flour
in order to make a dough of predetermined
consistency (normal consistency). A plot of
dough consistency versus time is recorded, as
shown in Fig. 15.26.
In addition to the water absorption, the shape of
the farinogram is used to characterize a flour. Var-
between the contents of SH- and SS-groups in
flour, or their ratios, would be reflected in baking
quality. However, low correlation coefficients of
about 0.6 have been found. This corresponds to
the observation (15.4.1.4.1) that the relationships
are much more complex and cannot be grasped
by means of an easily determinable characteristic
quantity.
Of all enzymes in flour, quality control is aimed at
the determination of amylase activity. The Falling
Number test (Hagberg and Perten) servesthis
aim. A piston-type mixer falls through an aqueous
flour paste. The falling time of the piston is measured
for a given distance under standard conditions.
The results are related, among other things,
to starch granule stability in the presence of amylase
enzymes. The dextrin value should be determined
to assess amylase activity specifically. In
a method developed by Lemmerzahl, the extent
of standard dextrin hydrolysis in the presence of
flour extract is measured. The fermentation power
of a flour (cf. 15.4.1.6.1) involves determination
Fig. 15.25. Farinograph (according to Rohrlich and
Thomas, 1967). The apparatus consists of a thermostated
mixer or kneader (1), its blades are driven by
an electromotor (2). The reaction torque acts through
a lever system (4) of analytical balance precision on the
indicator scale (5) simultaneously recorded on a strip
chart recorder (6). The movement of the lever system is
damped by an oil dash pot (3). The farinogram is a diagram
of force versus time