Chemistry Reference
In-Depth Information
properties compared with yeasted dough.
183
During this proteolysis, mainly HMW glutenin
subunits are broken down, leading to increased glutenin solubility and reduced ability for
network formation.
184
The effects of proteases are strongly dependent on bread-making methods used, on flour
quality and on the presence of other functional ingredients. In a short process, the effects of a
protease on mixing requirements were found to be negligible, whereas effects on volume and
bread score were strongly dose dependent: at low dose rate there was a clear improvement in
volume and bread score, whereas, at especially higher dose rates, overall bread score greatly
reduced.
185
On the other hand, in a sponge and dough system, proteases greatly reduced
mixing time.
186
In shelf stable bread systems, proteases reduced the firmness of the crumb
more than other enzymes and also reduced moisture migration.
187
In both cases, effects of
these proteases on dough volume were limited, but proteases had a strong reducing effect on
crumb firmness and bread score.
185, 186
Most of the effects mentioned are derived from modification of the gluten proteins. Limited
proteolytic hydrolysis with a degree of hydrolysis (DH) of 0-5%, leads to an increase in gluten
solubility, in combination with an improvement of the emulsifying and foaming properties
of the gluten. The released soluble peptides had decreased functional properties.
188
Proteases can have major disadvantages. The action of the proteases is not limited in time,
they continue after mixing and weaken the dough structure in time. This phenomenon in-
creases the risk of weakening the dough and increases the stickiness of the dough. Sometimes
their action is even enhanced by the pH drop during fermentation. The use of proteases in
baking requires strict control of the bulk fermentation and proofing conditions of the dough.
Almost all proteases are inactivated during baking. Especially care should be exercised when
using neutral Bacillus proteases and papain, which should be dosed very carefully as over-
dosing will slacken the dough too much. This may result in dough collapse before baking or
a lower bread volume and a more open crumb structure. Particularly in Europe, where the
flours are weaker than in the US or Canada, the risk of overdosing a protease is very much
present. Furthermore, proteases also increase stickiness because by hydrolytic action, water
is released from the gluten. This means that in practice proteases are little used in bread
making in Europe.
6.6.2.2
Freshkeeping
Proteases have also been investigated in relation to freshkeeping. As mentioned above, there
are several ingredients (emulsifiers, fats, mono- and oligosaccharides) and processing tools
(specific amylases) known to retard bread staling. As there was not always a good correlation
between starch structure and staling, other flour constituents were also investigated. The role
of flour proteins in the crumb firming process has been studied but it was found that they
were less important than starch.
189
Nevertheless, upon using an intermediate thermostable or thermostable protease in baked
goods a pronounced effect on crumb softness and on retarding the staling of baked products
was found.
190
The enzymes used had specific characteristics; no adverse effect on dough
rheology, on crumb structure or the volume of the resulting bread; low activity at room
temperature; and a relatively high optimum temperature. Such an activity pattern guarantees
limited protein breakdown at temperatures encountered during mixing and proofing and
higher breakdown in the early stage of the baking process. The enzymes used showed similar
effects on a range of baked products.
