Food Chemistry

15.4 Baked Products 713

Fig. 15.24.Examples of relationship between pro-
tein 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

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. TheFalling
Number test (HagbergandPerten)servesthis
aim. A piston-type mixer falls through an aqueous
flour paste. The falling time of the piston is meas-
ured for a given distance under standard condi-
tions. The results are related, among other things,
to starch granule stability in the presence of amy-
lase enzymes. Thedextrin valueshould be deter-
mined to assess amylase activity specifically. In
a method developed byLemmerzahl, 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

of themaltose value(diastatic activity). This is

a quantitative determination of reducing sugars

prior to and after incubation of a flour suspen-

sion at 27◦C for 1 h. Flours with a maltose con-

tent of< 1 .0% are regarded as weak fermenta-

tion promoters; values above 2.5% are flours from

sprouted kernels. They provide poor baking qual-

ity.

15.4.1.1.2 Physical Assays

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 develop-

ment 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-

Fig. 15.25.Farinograph (according toRohrlichand

Thomas, 1967). The apparatus consists of a ther-

mostated 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 dia-

gram of force versus time