Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2157718
GIST-BROCADES B.V.
2706S
IMPROVEMENT OF BREAD DOUGHS
The present invention relates to improvement of
doughs for baked products, especially bread doughs. In
particular, it relates to use of enzymes, e.g. in the form
of a bread improver composition, to improve the properties
5 of such doughs.
Conventional bread improvers are complex mixtures
containing various functional ingredients such as oxidizing
and reducing agents (e.g. ascorbic acid, cysteine), enzymes
(e.g. ~-amylase, hemicellulase), emulsifiers (.e.g. DATA-
10 esters, monoglycerides, SSL), fatty materials (e.g. fat,lecithin) and carriers or bulk materials (starch, sugars,
etc). Many of the commonly used bread improvers contain
chemical oxidants such as ascorbic acid and bromate which
are used to increase the strength of the dough. From the
15 consumer's point of view, it is advantageous to minimise the
use of these oxidants, which are considered as chemical
additives. The resistance of consumers to chemical additives
is growing and there is therefore need to replace
conventional dough oxidants by consumer friendly additives.
20 However, bread quality is lowered considerably when oxidants
are omitted. Indeed, it is difficult to achieve a suitable
dough for a baked product without using oxidants.
Sulfhydryl oxidase has previously been investigated
as a substitute for conventional non-enzymic oxidants in
25 bread doughs. Bovine sulfhydryl oxidase as a single enzyme
additive in such doughs has, however, been reported to have
no significant beneficial effect on dough properties
(Kaufmann and Fennema, Cereal Chemistry (1987) 64 (3), 172-
176). Microbial sulfhydryl oxidase has previously been
30 reported to be useful as a bread dough additive, but only in
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combination with glucose oxidase (see EP-A 0321811) or in
combination with glucose oxidase and hemicellulose and/or
cellulose degrading enzyme activity (see EP-A 0338452).
We have now surprisingly found that addition of
5 sulfhydryl oxidase, e.g. a microbial sulfhydryl oxidase, to
a bread dough can have a beneficial effect on dough
properties in combination with addition of one or more
hemicellulases even in the absence of glucose oxidase.
Importantly, such an enzyme combination can be used in bread
10 doughs in preference to non-enzymic oxidants such as
ascorbic acid and bromate. By including such an enzyme
mixture in a bread dough, it is possible to improve loaf
volume while maintaining or even increasing dough
extensibility. In contrast, it is well known that use of
15 ascorbic acid to improve loaf volume will have a negative
effect on dough extensibility. This is particularly
unfavourable in the production of baked products such as
French sticks, baguettes, pizza and croissants for which a
high dough extensibility is desirable.
Hemicellulloses in cereal products mainly consist of
~-glucans and pentosans. The desirability of a moderate
hydrolysis of pentosans in bread doughs has long been
recognized (Enzymolysis of pentosans of wheat flour, K.
Kulp, Cereal Chem. (1968) 45, 339-350). Aspergillus niger
25 and Aspergillus awamori hemicellulases are widely used in
the baking industry. The inventors for the present invention
have found that among hemicellulases, two types are
particularly useful for use in bread doughs in combination
with sulfhydryl oxidase: endoxylanases and
30 arabinofuranosidases. Two arabinofuranosidase isoenzymes
have been identified: arabinofuranosidase A (Ara A) and
arabinofuranaosidase B (Ara B). For the purpose of the
present invention, an arabinofuranosidase preparation
comprising as the enzyme component at least predominately
35 Ara B is preferred. Ara A and Ara B are described in 'Mode
of action of (lt4)~-D-arabinoxylan arabinofuranohydrolase
(AXH) and ~-L-arabinofuranosidase on alkali extractable
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wheat flour arabinoxylans' Carbohydrate Research (1993), 24,
345-353, F.J.M. Xormelink; H. Gruppen; A.G.J. Voragen.
For the purpose of dough-making according to the
present invention, sulfhydryl oxidase may be derived from
5 Asperqillus niger as described in Asperqillus niger
sulfhydryl oxidase, R.S. de la Motte, F.W. Wagner,
Biochemistry 26(1987)7363-7371.
In one aspect, the present invention thus provides a
method of preparing a dough for a baked product which
10 includes incorporating into the dough an effective amount of
endoxylanase and an effective amount of sulfhydryl oxidase
in the absence of glucose oxidase so as to increase the
volume of the baked product and produce a dough
extensibility of at least 98% of the extensibility of the
15 same dough minus improver additives.
According to another aspect of the invention an
effective amount of an arabinofuranosidase-preparation, most
preferably an arabinofuranosidase preparation in which Ara B
is the major isoenzyme of the enzyme component and an
20 effective amount of sulfhydryl oxidase, can be incorporated
into the dough so that both loaf volume and dough
extensibility are improved.
The present invention may be applied to a variety of
dough preparation processes including direct proofing,
25 retarded dough processes, sour dough processes and frozen
dough processes. It may be applied with flours from varied
cereals such as wheat or rye to manufacture all kinds of
yeast-leavened flour products such as bread as well as
sweetened products such as cakes.
As hereinbefore indicated, the methodology of the
present invention is, however, particularly favourable for
application in the production of baked products for which
extensibility of the dough is a critical factor for product
quality. Use of enzymes in accordance with the present
35 invention is, for example, especially favoured for the
preparation of French bread doughs suitable for production
of French sticks or baguettes.
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In a dough-making process of the present invention,
the required enzymes may be added separately or in the form
of a mixed enzyme composition. In a further aspect, the
present invention thus provides an enzyme composition for
s use in a dough-making method of the invention wherein the
enzyme component comprises endoxylanase and sulfhydryl
oxidase in the absence of a glucose oxidase, preferably
together with one or more arabinofuranosidases. Most
preferably, such an enzyme composition will include
10 endoxylanase, sulfhydryl oxidase and arabinofuranosidase at
least predominantly of the B isoenzyme form.
In a further -embodiment, the present invention
provides an enzyme composition wherein the enzyme component
comprises endoxylanase, sulfhydryl oxidase and
15 arabinofuranosidase, preferably at least for the major part
Ara B.
An enzyme composition of the present invention may
be in the form of a bread improver composition containing
one or more additional dry dough ingredients e.g. one or
20 more of salt, sugar, lecithin, gluten, soya flour, malt and
other enzymes known for use as baking ingredients such as ~-
glucosidase, ~-glucanase, ~-xylosidase, amyloglucosidase,
amylase, proteases, peroxidase and catalase. Such a bread
improver composition may include all or a large proportion
25 of the flour of the baked product.
The amounts of endoxylanase, sulfhydryl oxidase and
arabinofuranosidase required for a dough-making process of
the present invention will depend upon the flour employed
and the type of process and may be readily determined by
30 baking tests. By way of guidance, however, the amount of
endoxylanase may be in the range 1-1000 units per kg flour,
e.g. 5- 200 units per kg flour, and the amount of sulfhydryl
oxidase may be in the range 5-1000 units per kg flour, e.g.
30-250 units per kg flour. When it is desired to
35 additionally provide arabinofuranosidase activity in the
dough, this may, for example, be present in the range 1-1000
units per kg flour, preferably in the range 5-200 units per
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kg flour. As hereinbefore indicated, such activity may
desirably be provided by use of an arabinofuranosidase
preparation in which Ara B is the major isoenzyme of the
enzyme component.
For making a French bread dough suitable for French
sticks or baguettes, it has, for example, been found
favourable to incorporate about 50 units of sulfhydryl
oxidase per kg of flour in combination with about 70 units
of endoxylanase per kg of flour. To obtain improved dough
10 extensibility in addition to improved loaf volume, such an
enzyme combination may suitably supplemented with about 70
units of arabinofuranosidase, largely Ara B (see Example 2).
Units of endoxylanase, sulfhydryl oxidase and
arabinofuranosidase as given herein should be understood to
15 be units defined with reference to the following assays.
Endoxylanase (Lyx) activity is measured by the
hydrolysis of xylan from oat spelts suspended (35 g/l) in lM
glycine buffer pH 2.75. The viscosity of the solution is
determined by using a capillary viscosimeter (Ubbelhode
20 type) at 47C. The time (t) needed for the upper meniscus of
the liquid to fall down between two reference points is
measured within time (T). The slope of the plot of T versus
l/t yields an apparent kinetic constant. 1 Lyx unit is the
amount needed to reach a value of 1 min~1 for that kinetic
25 constant.
Arabinofuranosidase (Arf) activity is measured by
the hydrolysis of p-nitrophenyl-arabinofuranoside. One arf
unit is the amount of enzyme needed to liberate 1 ~mole p-
nitrophenol per minute under the conditions of the test
30 described in 'Purification and some properties of an
arabinofuranosidase from Aspergillus niqer, action on grape
monoterpenyl arabinosylglycosides', Z. Gunata, J.M.
Brillouet, S. Voirin, R. Baumes, R. Cordonnier, J. Agric.
Food Chem. 38 (1989) 772.
Sulfhydryl oxidase (Sox) converts thiol compounds to
their corresponding disulfides according to the equation:
2 RSH + 2 ~ RSSR + H202
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Sox activity is determined by measuring the
disappearance of glutathione in buffer solution in the
presence of oxygen. One sox unit is the amount of enzyme
needed to oxidize 1 ~mole glutathione per minute at 30C and
5 pH 7.
Legend to the Figure
Results from alveograph test as described in Example
1. Ref. no enzymes nor ascorbic acid added. Lyx+Sox (calc.)
10 iS calculation of the effect of Lyx + Sox assuming no
synergy. Lyx+Sox (Exp.) is experimental result of Lyx + Sox.
Example 1
In order to determine the rheological effects of
15 enzymes and ascorbic acid (AA) separately, the following
experiment was performed.
A virgin flour, devoid of any additives or
processing aid, was used. Ascorbic acid or an enzyme
composition was added according to Table 1. An alveograph
20 was operated according to a standard procedure AFNOR V-03-
710. Alveograph traces were drawn from a Chopin alveograph:
kneading at 24C for 20 minutes.
Table 1
Test No. AA (ppm) Units Lyx Units Sox
0 0 o
2 0 70 o
3 0 0 500
4 0 70 500
100 0 0
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Table 2
Test No. P L W
1 76 75 179
2 76 76 181
3 86 70 206
4 78 77 204
103 63 220
In Table 2 the rheological properties of the formed doughs
are shown. The P-value is related to tenacity of the dough,
L is related to elasticity and W to strength of the dough
15 (AFNOR V-03-710). A desirable result is an increase in
strength (W) in combination with an increase of the
elasticity (L) and a reduction of the tenacity (P).
It is clear that ascorbic acid increases the
strength of a dough. However, at the same time an
20 undesirable reduction of the elasticity and an increase of
the tenacity occurs. As in the case of chemical oxidizing
agents, Sox also increases the strength and the tenacity,
but reduces the elasticity. In the Figure, the effect of
Lyx, Sox and the combination Lyx + Sox is shown on the
25 parameters P, L and W. From the effect of Lyx and Sox alone,
a combined effect can be calculated (Lyx + Sox (Calc.)). The
effect is compared with the experimental result (Lyx + Sox
(Exp.)). This shows that a combination of Sox and Lyx
results in strong favourable synergy on extensibility and
30 tenacity, while at the same time the strength of the dough
is not decreased significantly.
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Example 2
Dough was prepared by mixing:
2 kg French virgin flour, 45 g sodium chloride, 70 g baker's
yeast, enzymes and/or AA (see Table 3 below; units are units
5 per kg flour) and 1.2 litres water cooled at 4C, kneading
for 15 minutes and then
- leaving one part in a proofing system for
fermentation; the height of that dough piece after 3 hours
fermentation enabled evaluation of the tolerance of the
10 dough;
- mechanically shaping the remaining part into
baguettes and measuring the length. This enabled evaluation
of the extensibility of the dough. The baguettes were left
for fermentation at 20C for lh 45 mins
15 and finally baked for 20 minutes at 225C. Loaf volumes of
baked breads were measured.
Table 3
Test No. Units Lyx Units Arf Units Sox AA (ppm)
1 0
2 0 0 0 80
3 40 10 0 80
4 70 0 50 0
70 (AraB) 50 0
6 70 70 (AraA) 50 0
7 0 70 (AraB) 50 o
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g
Table 4
Test No. Extensibility Dough Tolerance Loaf Volume
(cm) (mm)
1 70 70 2940
2 65 69 3080
3 69 67 3227
4 69 69 3258
69 3265
6 69 67 3200
7 69 73 3280
As shown in Table 4, the addition of ascorbic acid
alone improved the loaf volume. However, it also reduced the
extensibility of the dough. As hereinbefore mentioned, this
reduction in dough extensibility is a negative aspect of the
application of ascorbic acid.
Ascorbic acid was also tested in combination with
Lyx and Arf, an additive combination known for use in
20 baking, (test no. 3). Ara B was the major isoenzyme in the
Arf preparation.
In test no. 4, an enzyme combination was
investigated that resulted in a loaf volume even higher than
that observed with the combination of ascorbic acid with Lyx
25 and Arf. The extensibility was the same as for the
combination of ascorbic acid with Lyx and Arf.
Dough extensibility was found surprisingly to be
further improved by the addition of Arf without any negative
effect on dough tolerance or loaf volume (test no. 5).
Comparison of results obtained in tests no. 5 and 6
show that Ara B performs better than Ara A with regard to
extensibility and loaf volume mainly.
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Dough tolerance and loaf volume were found
surprisingly to be optimal with the combination of Sox and
Arf replacing ascorbic acid (test no. 7).
