Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SPECIFICATION
PROCESS FOR MAKING BREAD
Technical Field
This invention relates to a process for making bread
being excellent in the specific volume, etc.
Background of the Invention
In the bread-making trade, freeze-storage dough
(frozen dough) is widely used as a means for the
rationalization of production. Very high energy costs are
required for freezing, freeze-storage, freeze-transportation,
thawing, etc. In order to reduce these energy costs, a dough
which is capable of being stored through refrigeration is used
[Report by Katsuro Kaitaku Chosa Kenkyu Jigyo (active
development investigation project), 36 - 45 (1990); B & C, 26
- 37 (1990); Basic Knowledge for New Bread Making, 148 - 180
(July 10, 1988, 7th edition)]. However, the dough capable of
being stored through refrigeration poses a problem with
respect to the storage stability of the yeast contained in the
dough, because the yeast deteriorates during the long-term
storage.
Further, fat and oil such as butter, margarine, etc.
are folded into the dough in the production of a Danish
pastry, croissants, etc., and the uniform layers of the dough
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and the fat and oil are indispensable to making a good
product. To satisfy this requirement, the folding of the fat
and oil is ordinarily conducted batchwise. In each batchwise
operation, increase in the temperature of the dough and the
temperature of the fat and oil affects the extensions of the
dough and the folded fat and oil. For this reason, a so-
called retarding method is employed in which the freezing is
repeatedly carried out in a refrigerator. With the ordinary
yeast, fermentation proceeds, and thus the remaining activity
of the yeast is lowered at the time when the fermentation is
completed. In addition to the deterioration of the yeast due
to the storage through refrigeration, the bread making by the
retarding method involves a lot of problems.
Still further, when an ordinary yeast is contained
in a refrigeration-storage dough for a domestic purpose (which
is mostly packed in a sealed container), the refrigeration-
storage dough has no storage stability and therefore the dough
is degraded. In order to prevent the degradation of the
dough, a chemical foaming agent is used instead of the yeast
in many cases. Nevertheless, such a dough cannot give a
satisfactory bread product in regard to flavor, appearance,
etc.
Disclosure of the Invention
This invention relates to a process for making bread
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t
characterized in that a yeast of the genus Saccharomyces which
exhibits cold-sensitive fermentation is added to a dough.
In this invention, any yeast of the genus
Saccharomyces can be used so long as it exhibits cold-
sensitive fermentation.
In the present specification, the cold-sensitive
fermentation means that the yeast is normally fermented at
from 20 to 40°C and shows a fermentability which is the one
third or below, of that of a commercial yeast at a temperature
of from -2 to 15°C. The yeast used in this invention can be
obtained, for example, by the following method. Cells of a
commercial yeast (for example, baker's yeast, sake yeast, wine
yeast, beer yeast and yeasts of miso and soy sauce) are
mutagenized by irradiating with an ultraviolet light,
radiation, etc. according to a known mutation-inducing method.
The mutagenized cells are contacted with antibiotics (for
examples, antimycin and nystatin), and cultivated at a low
temperature of from 10 to 15°C. Cells which cannot be
proliferated or which exhibit very low proliferation at these
low temperatures are selected (primary selection). The
strains which are selected in this primary selection include
strains which cannot be proliferated or which exhibit very low
proliferation because of lack of fermentability or a very low
level of fermentability and strains which exhibit low
proliferation due to the other causes. From among these
strains, selected are the strains which lack fermentability or
' -
4 -
have a very low level of fermentability at a low temperature
of from 2 to 7°C (secondary selection). Then, from among the
strains selected in the secondary selection, selected are the
strains which regain fermentability at a temperature of from
20 to 40°C (tertiary selection). Finally, from among the
strains selected in the tertiary selection, selected are the
strains which exhibit as excellent a fermentability as the
ordinary yeast under the fermentation conditions of the bread
dough at a temperature of from 20 to 40°C (quaternary
selection).
A specific example of the strains thus selected is
Saccharomyces cerevisiae RZT-3 (hereinafter referred to as
"RZT-3 strain").
A method for obtaining RZT-3 strain is described
below.
Commercial bread yeast Dia Yeast YST (made by Kyowa
Hakko Kogyo Co., Ltd.; hereinafter referred to as "YST
strain") is cultivated in a YPD culture medium comprising 1~
of yeast extract, 2~ of polypeptone and 2~ of glucose at 30°C
for 12 hours, and centrifuged to collect cells. The collected
cells are suspended in an aqueous solution of 0.067 M
potassium dihydrogenphosphate with an absorbance of 1.0, that
is, such that the number of cells being 1 x 10~ per
milliliter. The cell suspension is irradiated with
ultraviolet light to the extent that the survival rate is from
1 to 30~, and then subjected to the primary selection.
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The primary selection is conducted in the following
manner. Twenty microliters of the resulting cell suspension
is inoculated in 1 ml of the YPD culture medium and cultivated
at 30°C for 12 hours. After the cultivation is completed,
cells are collected by centrifugation. The collected cells
are cultivated in a nitrogen-free minimum culture medium
comprising 0.17 of yeast nitrogen base having no amino acid
and no ammonium sulfate (made by Difco) and 1~ of glucose at
30°C for 12 hours. After the cultivation is completed, the
cells are re-collected by centrifugation. The collected cells
are suspended in 0.9 ml of a YPD culture medium containing 1
x 10-6M antimycin, and cultivated at 10°C for 36 hours.
Further, 10 ,ug/ml nystatin is added to the culture,
and the culture is allowed to stand at 10°C for 2 hours. The
culture is centrifuged to collect cells. The collected cells
are spread on a YPD plate culture medium comprising 1$ of
yeast extract, 2~ of polypeptone, 2~ of glucose and 2~ of
agar, and cultivated at 30°C for 48 hours to grow colonies.
The grown colonies are selected as follows to thereby obtain
RZT-3 strain. The RZT-3 strain was deposited with the
Fermentation Research Institute Agency of Industrial Science
and Technology on May 26, 1992 in terms of the Budapest
Treaty, and has been assigned to Accession No. FERM BP-3871.
The secondary selection is conducted as follows.
The colonies separated in the primary selection are
transferred on to a YPG plate culture medium comprising 1~ of
- _ 2~.46~~~
yeast extract, 2$ of polypeptone, 3~ of glycerol and 2$ of
agar, and cultivated at 30°C for 24 hours to grow colonies. A
pigment agar culture medium comprising 0.5~ of yeast extract,
1~ of peptone, 10~ of sucrose, 0.02 of bromocresol purple and
l~ of agar is ovelayed on the colonies. The colonies are
inoculated at 5°C for from 6 to 12 hours. During this time
period, the color around the colonies is observed, to select
the strains having strong fermentability. That is, the
strains having strong fermentability at 5°C, change in the
color from purple to yellow and the strains which lack
fermentability or have low fermentability, do not or slightly
change in the color.
The tertiary selection is conducted as follows. The
colonies selected in the secondary selection are transferred
on a YPG plate culture medium, and cultivated at 30°C for 24
hours to grow colonies. The pigment agar culture medium is
overlayed on the colonies, and the colonies are cultivated at
30°C for 2 hours. The strains having sufficient
fermentability (the strains which change in the color around
the colonies from purple to yellow) are selected.
The quaternary selection is conducted as follows.
With respect to the strains selected in the tertiary
selection, a bread dough is prepared to have the following
composition by the following method. The amount of a carbon
dioxide gas generated at from -2 to 40°C is measured and
employed as a criterion for determination of fermentability.
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Dough composition: (Parts by weight)
Strong flour 100
Sugar 15
Salt 1.2
Water 58
Yeast cells obtained
in Example 1 hereinafter 3
Method:
Mixing (with a National complete mixer at 100 rpm
for 2 minutes)
Fermenting (at 30°C for 45 minutes)
Dividing (35.448)
Allowing to stand (at 10°C for 3 hours)
Measuring the amount of the carbon dioxide gas which
is generated at temperatures shown in Table 1 for 2
hours.
The amount of carbon dioxide gas generated at from
-2 to 15°C for 2 hours is measured by a method in which 35.448
of the bread dough are packed in a 100-milliliter conical
flask and the carbon dioxide gas generated is moved into a
cylinder filled with a saturated NaCl aqueous solution. The
amount of the carbon dioxide gas generated at from 20 to 40°C
~ ~ _ 8 _ _ 2~4~24~
is measured with a Fermograph (supplied by ATTO CO., LTD.).
The results are shown in Table 1.
Table 1
Amount
St of carbon
i dioxide
gas generated
(ml)
ra
n -2C 0C 2.5C 5C 10C 15C
YST 0.0 0.5 1.1 2.0 14.3 26.0
RZT-3 0.0 0.0 0.0 0.2 2.9 7.1
Amount
i of carbon
dioxide
gas generated
(ml)
- -
Stra 20C 25C 30C 35C 40C
n
YST 65.7 91.7 145.8 190.9 211.2
RZT-3 59.9 93.5 147.9 188.3 221.9
As is apparent from the table, YST strain does not
substantially ferment at -2°C and 0°C, and the ability of the
fermentation is gradually increased at 2.5°C or higher.
Meanwhile, RZT-3 strain does not substantially ferment at from
-2 to 5°C, and the ability of fermentation of RZT-3 strain is
approximately one third of that of the YST strain even at
15°C, and is approximately the same as that of the YST strain
at 20°C or higher.
In the present invention, as the dough to which
yeast is added, any dough can be used, so long as the dough is
obtained by adding water to a wheat flour and a salt.
Specifically, a dough which is obtained by adding, if
,
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necessary, sugar, shortening, butter, skim milk, yeast food
and egg to raw materials such as a wheat flour, a salt and fat
and oil, is mentioned, and kneading the mixture together with
water.
A method for making bread is described hereinafter.
Cultivation of bread yeast
Yeast cells which are suitable for making bread can
be obtained by cultivating yeast in an ordinary culture medium
containing a carbon source, a nitrogen source, an inorganic
substance, amino acid and vitamin under aerobic conditions
while adjusting the temperature to from 27 to 32°C, recovering
the cells and washing the recovered cells.
The carbon source to be contained in the culture
medium includes, for example, glucose, sucrose, starch
hydrolyzate and molasses. Blackstrap molasses is the most
preferable.
The nitrogen source to be contained in the culture
medium includes, for example, ammonia, ammonium chloride,
ammonium sulfate, ammonium carbonate, ammonium acetate, urea,
yeast extract and corn steep liquor.
The inorganic substance includes, for example,
magnesium phosphate and potassium phosphate. The amino acid
includes, for example, glutamic acid. The vitamin includes,
for example, pantothenic acid and thiamine. Feeding culture
is suitable in the cultivation.
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Method for making bread
The bread dough to be used is obtained by adding, to
a wheat flour, a salt, fat and oil, water, the above-obtained
yeast and, if necessary, sugar, shortening, butter, skim milk,
yeast food and egg. Bread in the form of a loaf of bread, a
bun or the like can be made according to the typical method,
for example, the straight dough method and the sponge and
dough method. The former is a method in which all the raw
materials are mixed from the beginning. The latter is a
method in which yeast and water are first added to a part of
wheat flour to form a sponge mix, and after the completion of
the sponge fermentation, the remaining raw materials and mixed
with the sponge fermentation.
Specifically, in the straight dough method, all the
raw materials are kneaded, then fermented at from 25 to 30°C,
divided, benched, molded and packed. The resulting product is
subjected to proofing (at form 35 to 42°C), and then baked (at
from 200 to 240°C).
Separately, in the sponge and dough method, water is
added to approximately 70~ of the wheat flour used, yeast and
yeast food, and the mixture is kneaded and fermented at from
25 to 35°C for from 3 to 5 hours. Thereafter, the remaining
raw materials (wheat flour, water, salt and shortening) are
thereto. The mixture is kneaded, divided, benched, molded and
packed. The resulting product is subjected to proofing (at
from 35 to 42°C) and then baked (at from 200 to 240°C).
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A Danish pastry, croissants, etc. are made, for
example, in the following manner.
Water is added to raw materials, that is, a wheat
flour, a salt, the above-obtained yeast, sugar, shortening,
egg and skim milk, and the mixture is kneaded to form a dough.
Then, fat and oil such as butter, margarine, etc. are put into
the dough. Rolling and folding are repeated to make multiple
layers of the dough and the fat and oil. The step of folding
the fat and oil when the dough is prepared, is called rolling-
in. The rolling-in can be accomplished by either of two
methods. In one method, the raw materials are kneaded at a
low kneading temperature of approximately 15°C without cooling
until the intended number of layers are given. In the other
method, during the folding, the difference between the
extension of the dough and the extension of the fat and oil
due to the increase in the temperature of dough and the fat
and oil damages uniformity of the layers. The other method is
the so-called retarding method in which the cooling is
conducted several times in a refrigerator or a freezer for the
purpose of restoring the properties of the dough during the
operation.
The obtained dough is rolled, divided, molded and
packed. The resulting dough is subjected to proofing (at from
30 to 39°C), and then baked (at from 190 to 210°C).
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Best Mode for Carrying out the Invention
This invention is illustrated specifically with the
use of the following Examples.
Example l:
Cultivation of bread yeast
One platinum loopful of RZT-3 cells was inoculated
in a 300-milliliter conical flask containing 30 ml of a YPD
culture medium, and cultivated at 30°C for 24 hours. After
the cultivation was completed, the total amount of the culture
was put into a 2-liter conical flask equipped with a baffle
and containing 270 ml of a molasses culture medium comprising
3~ of molasses, 0.193 of urea, 0.046 of potassium
dihydrogenphosphate and 2 drops of a deformer, and cultivated
at 30°C for 24 hours with shaking. After the cultivation was
completed, the cells were collected by centrifugation. The
cells were washed twice with deionized water. Subsequently,
the moisture content was removed to an absorptive ceramic
plate to obtain the cells.
Also, YST cells were subjected to the same procedure
as the RZT-3 cells.
The thus-obtained yeast cells were used to make
bread.
Making bread
A loaf of bread was obtained from the following
dough composition and by the following method.
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Dough composition: (parts by weight)
Strong flour 100
Sugar 5
Salt 2
Shortening 5
Yeast food 0.1
(Pandia C-500 made by
Kyowa Hakko Kogyo Co., Ltd.)
Yeast cells 2
(RZT-3 strain or YST strain)
Water 66
Method:
Mixing [low speed (100 rpm) 3 minutes
medium speed (190 rpm) 6 minutes
high speed (290 rpm) 5 minutes
Kneading temperature (28°C)
Dividing (450g)
Storing (5°C, 7 days)
Benching (room temperature, 15 minutes)
Molding (molder)
Proofing (40°C, 90~RH, 75 minutes)
Baking (220°C, 25 minutes)
The fermentability before and after refrigeration
(storage at 5°C for 7 days) was measured by a Fermograph using
30g of the dough, and the total amount (ml) of the carbon
dioxide gas generated at 30°C for 2 hours was shown. The
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refrigeration resistance was calculated by the following
equation.
Refrigeration resistance
Fermentability (ml) after refrigeration
x 100
Fermentability (ml) before refrigeration
The results are shown in Table 2.
Table 2
Fermentability Fermentability
Strain before after Refrigeration
refrigeration refrigeration resistance
(ml) (ml)
YST 114.6 40.0 34.9
RZT-3 108.9 99.7 91.6
The specific volume of the obtained loaf of bread
was measured by a rape seed displacement method. Further,
appearance and crumb grain were observed. The results are
shown in Table 3.
Table 3
Specific volume Evaluation
Strain -- .-
( cm3~g ) Appearance Crumb grain
YST 3.19 x x
RZT-3 4.79 ~
Note: Evaluation standard ~ . good
x . poor
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Examble 2:
A butter roll was obtained according to the
following dough.composition and by the following method.
Dough composition: (parts by weight)
Strong flour 80
Soft flour 20
Sugar 10
Salt 1.8
Salt-free butter 15
Skim milk 3
Whole egg 8
Yeast food (Pandia C-500) 0.1
Yeast cells 3
(RZT-3 strain or YST strain)
Water 54
Method:
Mixing [low speed (100 rpm) 10 minutes
medium speed (190 rpm) 5 minutes
high speed (290 rpm) 30 seconds
Kneading temperature (26°C)
Dividing (50g)
Benching (room temperature, 15 minutes)
Molding (molder)
Storing (5°C, 1, 4 and 7 days)
Proofing (36°C, 85~RH, 40 minutes)
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Baking (210°C, 12 minutes)
In accordance with Example l, the fermentability and
the specific volume were measured, the refrigeration
resistance was calculated, and the appearance and the crumb
grain were observed. The results are shown in Tables 4 and 5.
Table 4
Fermentability Refrigeration
(ml)
Strain
Before 1st day 4th day 7th day resistance
refrige- (after 7 days)
ration
YST 130.7 134.8 105.0 33.8 25.6
RZT-3 121.4 133.8 112.6 104.8 86.3
Table 5
Strain
Specific Evaluation
volume after 7 days
(cm3/g)
1st day 4th day 7th day Appearance Crumb grain
YST 4.38 4.09 2.86 x x
RZT-3 4.98 4.67 3.87
Example 3:
A Danish pastry was obtained according to the
following dough composition and by the following method
(retarding method).
. i: ~ -1~- _
Dough composition: (parts by weight)
Strong flour 70
Soft flour 30
Sugar 10
Salt 1.2
Shortening 6
Whole egg 10
Yeast food (Pandia C-500) 0.1
Yeast cells 6
(RZT-3 strain or YST strain)
Water 50
Folding butter 50
Method:
Mixing [low speed (100 rpm) 3 minutes
medium speed (190 rpm) 8 minutes
high speed (290 rpm)] 1 minute
Kneading temperature (22°C)
Dividing (1,OOOg x 2)
Retarding (-20°C, 30 minutes)
Rolling-in [folding into three layers, twice
(folding butter: 50~ per the wheat
flour)]
Retarding (5°C, 60 minutes)
Rolling (folding into three layers, once,
rolling at 4 mm)
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. ~ ~. ' _ 18 _ _
Dividing and molding
[50g, rolled shape (for fermograph,
30g.) ]
Storing (5°C, l, 4 and 7 days)
Proofing (35°C, 75~RH, 70 minutes)
Baking (200°C, 12 minutes)
The dough was divided, molded and then directly
baked without being stored, or the dough was divided, molded,
stored in a refrigerator of 5°C for 1, 4 and 7 days, and then
baked.
In accordance with Example 1, the fermentability and
the specific volume were measured, the refrigeration
resistance was calculated, and the appearance and the crumb
grain were observed. The results are shown in Tables 6 and 7.
Table 6
Fermentability Refrigeration
(ml)
Strain
Before 1st day 4th day 7th day resistance
refrige- (after 7 days)
ration
YST 207.3 208.8 135.5 61.7 30.1
RZT-3 204.2 200.2 161.1 161.9 82.3
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"~~ - 19 - _
Table 7
Specific volume
(cm3/g)
Strain Just after
baking 1st day 4th day 7th day
YST 5.20 4.99 3.86 3.40
RZT-3 5.30 5.20 5.10 4.85
Evaluation
Immediately 1st 4th 7th
day day day
Strain
_ _ _
ap crumb ap crumb ap crumb ap crumb
pear- grain pear- grain pear- grain pear- grain
ance ance ance ance
YST OO OO O O x x x x
RzT-3 Oo O O O O O O O
Note: Evaluation o0 . good
O . fair
x . poor
Example 4:
A butter roll was obtained according to the
following dough composition and by the following method.
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ff
l
Dough composition: (parts by weight)
Strong flour 80
Soft flour 20
Sugar 10
Salt 1.8
Salt-free butter 15
Skim milk 3
Whole egg 8
Yeast food (Pandia C-500) 0.1
Yeast cells 2.5
(RZT-3 strain or YST strain)
Water 54
Method:
(1) The raw materials of the above-mentioned dough
composition were mixed at low speed (100 rpm) for 10
minutes, at medium speed (190 rpm) for 5 minutes and at
high speed (290 rpm) for 30 seconds. The kneading
temperature was 26°C.
(2) The obtained dough was divided (50g), then
benched at room temperature for 15 minutes, and molded.
(3) After the molding was completed, the dough was
packed in a sealed container (filled with a carbon
dioxide gas), and immediately stored in a refrigerator of
5°C for from 1 to 5 weeks.
(4) After the storage, the dough was subjected to
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proofing at 36°C for 30 minutes, and baked at 210°C for
12 minutes.
The specific volume of the obtained butter roll is
shown in Table 8.
Table 8
Storage period
(weeks)
Strain Just after
baking 1 2 3 5
YST 4.72 2.86 2.30 2.25 2.11
RZT-3 4.82 4.22 3.88 3.69 3.32
