Chemistry Reference
In-Depth Information
Table 7.1
Comparison on the use of bacterial protease,
L
-cysteine and SMS in a Marie-type biscuit.
Biscuit characteristics
Density (g/cm
3
)
Processing aid
Dose
Length (cm)
Reference
0
29.2
1.30
16 800 PC kg
−1
Bacterial protease
29.5
1.21
L
-cysteine
80 ppm
29.5
1.21
SMS
220 ppm
29.7
1.22
L-Cysteine hydrochloride can be used as an alternative to SMS and is permitted for use
in biscuit production. However, due to its relative high cost in use compared with SMS it is
not routinely used.
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The use of protease to modify gluten quality has been known for quite some time.
Standardized protease tablets from
Aspergillus sp.
are available and can be used in cracker
sponges in order to increase dough extensibility. This allows cracker manufacturers tight
control over dough consistency.
67
Compared to sulphite, proteases work in a different way since they hydrolyze the inner
peptide linkages of gluten proteins, whereas SMS increases extensibility by breaking the
disulphide bonds. The texture of the biscuits obtained will also be more open and tender.
Compared to sulphite, enzymes are pH, temperature and time dependent; therefore dosage
should be higher in the case of cool doughs than with hot doughs. Additionally, pH increase
due to carbonate present in the biscuit dough may lower the enzymatic activities.
Different types of proteases can be used in order to hydrolyze the gluten network; however,
the most common practice is the use of a bacterial protease, for example originating from
Bacillus amyloliquefaciens
.
The comparison of SMS, L-cysteine and bacterial protease in a Marie-type biscuit is
shown in Table 7.1. Marie-type biscuits have been prepared according to a typical recipe.
After 25 min kneading at 35
◦
C, the dough has been laminated, cut-off and baked for 5 min at
280
◦
C. Finished biscuits have been cooled down for 30 min at room temperature before final
dimensions have been measured. As can be seen in Table 7.1, the final biscuit dimensions
obtained from dough containing bacterial protease match the dimensions obtained from
dough prepared with 80 ppm L-cysteine, and closely similar to the dough prepared with
220 ppm SMS.
However, microbial proteases will not be easy to manage with their continuous action
over time, not allowing the manufacturers a degree of freedom with regard to the resting time
of dough.
In 1997, it was proposed by Souppe
et al
.
70
that the use of an oxidation-sensitive protease,
such as papain, in combination with an oxidizing enzyme (such as glucose oxidase) producing
an oxidizing agent, can enable biscuit manufacturers to mimic the effect of sulphite in dough.
By using a protease that may be only active at the beginning of the dough preparation,
shrinking of the dough may be reduced and more regular sizes of baked products, such as
biscuits, can be obtained. The action of the protease can then be substantially decreased
when the concentration of the oxidizing agent has reached such a level that inactivation of
the protease will take place. This will be of particular benefit when left-over dough is fed
back into the system as rework.
From Fig. 7.5(b), it is clear that papain hydrolyzes the gluten to such a degree that the
resulting dough is not suitable for biscuit baking. The combination of papain and glucose
