2009_Book_FoodChemistry

720 15 Cereals and Cereal Products
Fig. 15.37. The effect of a proteinase preparation on resistance
to extension (in extensogram units) of a wheat
flour dough (according to Sproessler, 1980). Proteinase
preparation: 1 fungal, 2 papain, and 3 bacterial. U Hb
proteinase activity units determined with hemoglobin
as a substrate
Fig. 15.36. Farinograms. Effect of L-cysteine hydrochloride
on a flour with strong gluten (according to
Finney et al., 1971). A control (no addition), B cysteine
added (120 ppm)
of the dough decreases and the extensibility
increases (cf. Table 15.42). Decreases in dough
development time and dough stability, as shown
in farinograms (Fig. 15.36), clearly reveal the
addition of cysteine. Flours with strong gluten
and with optimum levels of cysteine also show
a favorable increase in baking volume since,
prior to baking, the gas trapped within the dough
can develop a more spongy dough. The action of
sodium sulfite is similar to that of cysteine.
15.4.1.4.5 Proteinases (Peptidases)
Proteinase preparations of microbial or plant origin
are used for dough softening (cf. 2.7.2.2.1).
Their action involves protein hydrolysis, i. e.,
gluten-protein endo-hydrolysis. Their effect on
dough rheology, therefore, depends on the nature
of the enzymes and the activity of the preparations
towards gluten proteins. This is shown
in Fig. 15.37. Despite equal hydrolase activities
with hemoglobin as a test substrate, a fungal
proteinase degrades gluten to a lesser extent
and consequently causes a smaller decrease in
dough resistance to extension in comparison to
a bacterial enzyme preparation. Also, the latter is
more effective than papain.
Fungal proteinases, because of their low enzyme
activity and, therefore, high dosage tolerance,
are suitable for optimization of flours containing
strong gluten, used for bread and buns. However,
bacterial enzymes are preferred in production of
biscuits and wafers since they degrade gluten
to a greater extent, providing accurate flat
dough pieces with high form stability. Bacterial
enzymes are also preferred for the desirable
end product qualities of porosity and breaking
strength.
Data are shown in Table 15.45 for white bread
prepared with and without papain. There is
a rise in the content of both free amino acids
in the crumb and volatile carbonyl compounds
in the crust when proteinase is used. As long
as proteinases are active in a baking process,
they release amino acids from flour proteins,
which are then changed via Strecker degradation
Table 15.45. Effects of papain addition in white bread
making (values in µmole/g dry matter)
Constituent Without With
papain papain
Free amino acids Dough 183 186
Crumb 182 272
Crust 10 15
Volatile carbonyl
compounds Crust 158 217