WO2008047596A1

WO2008047596A1 - Freeze-tolerant yeast

Info

Publication number: WO2008047596A1
Application number: PCT/JP2007/069335
Authority: WO
Inventors: Shingo Izawa; Yoshiharu Inoue; Kayo Ikeda; Sayuri Kitagawa; Yuko Furukawa
Original assignee: Fuji Oil Company, Limited
Priority date: 2006-10-18
Filing date: 2007-10-03
Publication date: 2008-04-24
Also published as: JPWO2008047596A1

Abstract

It is intended to provide a freeze-tolerant yeast. It is also intended to provide a frozen dough which shows an enough rise when fermented after the freezing and a bread made from this frozen dough. Moreover, it is intended to provide a method by which the freeze-tolerant yeast as described above is obtained. A yeast is cultured in a medium containing a protein digest. By using the thus obtained yeast, a frozen dough and a bread made from the frozen dough are produced.

Description

Specification

Freezing-resistant yeast

Technical field

TECHNICAL FIELD [0001] The present invention relates to a freeze-resistant yeast, a culture method for imparting freezing resistance to yeast, a frozen dough that undergoes fermentation after freezing using the freezing-resistant yeast, and a bread using the frozen dough .

Background art

[0002] Recently, the use of frozen bread dough has become popular in the bakery industry. Advantages of frozen bread dough include the ability for producers to save labor and increase efficiency and enable planned production, while consumers can purchase a wide variety of varieties. However, the yeast damage due to freezing is large, but the fermentation tends to be insufficient and the flavor of the bread tends to be poor. Further, yeasts imparted with freezing tolerance include Patent Document 1 (Japanese Patent Publication No. 59-25584), Patent Document 2 (Japanese Patent Publication No. 59-48607), Patent Document 3 (Japanese Patent Publication No. 63-58536), Patent Document 4 ( There are many reports such as Japanese Patent Publication No. 4 (20595) and Patent Document 5 (Japanese Patent Publication No. 6-87772), but they have not been fully resolved. In addition, even if these yeasts are used, they will be damaged or killed by freezing damage, so it is unnecessary to add 1-2 to 1.5 times the amount of yeast that is not frozen. . In addition, a unique odor that seems to be derived from yeast that has been given this freezing tolerance is produced, which impairs the flavor of bread. Patent Document 6 (Japanese Patent Laid-Open No. 9 234058) reports on a yeast having freezing tolerance that accumulates one or more amino acids selected from proline, arginine, lysine, or glutamic acid in the microbial cells! A special process such as a mutagenesis process is required, which is different from the structure of this patent.

On the other hand, methods for promoting fermentation by adding soybean protein enzyme-degraded products to fermented foods of yeast such as bread are disclosed in Patent Document 7 (JP-A-11-009175) and Patent Document 8 (JP-A-54- 67 052), which is the addition of a soybean protein enzyme degradation product to the bread dough itself, and is different from the present application in which yeast is cultured in advance using a soybean protein degradation product. Also, it is mentioned that it is freezing resistant! / ,! Patent Document 9 (Japanese Unexamined Patent Application Publication No. 2000-253805) The ability to blend corn protein zein peptide into fermented foods and to reduce the aging of bread dough without declining fermenting even if it is frozen and refrigerated. Therefore, the configuration is different from that of the present invention. In Patent Document 10 (Japanese Patent Application Laid-Open No. 08-019392), fermentation of lactic acid bacteria, yeast, etc. is promoted with an external solution obtained by fractionating the enzyme degradation product of soybean protein with a reverse osmosis membrane having a salt rejection of 25-80%. However, it does not mention freezing tolerance.

Patent Document 1: Japanese Patent Publication No.59-25584

Patent Document 2: Japanese Patent Publication No.59-48607

Patent Document 3: Japanese Patent Publication No. 63-58536

Patent Document 4: Japanese Patent Publication No. 20595

Patent Document 5: Japanese Patent Publication No. 6-87772

Patent Document 6: Japanese Patent Laid-Open No. 9 234058

Patent Document 7: Japanese Laid-Open Patent Publication No. U-009175

Patent Document 8: Japanese Patent Laid-Open No. 54-67052

Patent Document 9: Japanese Unexamined Patent Publication No. 2000-253805

Patent Document 10: Japanese Patent Application Laid-Open No. 08-019392

Patent Document 11: JP-A-62-143697

Patent Document 12: Japanese Patent Laid-Open No. 2001-238693

Patent Document 13: WO2005 / 089565

Patent Document 14: Japanese Patent Laid-Open No. 200-238693

Patent Document 15: Japanese Patent Laid-Open No. 62-014796

Disclosure of the invention

Problems to be solved by the invention

[0003] The present invention

Means for solving the problem

[0004] The present inventors added a soybean protein degradation product to bread dough and fermented it after freezing. Normally, the bread swelling during fermentation was inferior due to yeast damage caused by freezing. It was found that a bulge close to that obtained when freezing was obtained. To the bread dough Increasing the amount of soy protein breakdown product will give off a nasty and off-flavor derived from soybeans, even if bread bulges are obtained. In addition, the soy protein degradation product inhibits the ss binding of dullten in bread dough, which causes the dough to droop. Alternatively, there was a problem that the whip was swollen but the kettle dropped when firing. As a result of intensive research, we used yeast previously cultured in a medium containing a protein breakdown product and prepared frozen bread dough without adding the protein breakdown product to the bread dough. Rather than adding a decomposed product to the bread dough, a better bulge was obtained, and it was found that the previous difficulties such as dough dripping, kettle dropping, and deterioration of the bread dough flavor could be avoided, and the present invention was finally completed. .

Usually, yeast is cultivated in a medium in which waste molasses from which impurities have been removed, which have been sterilized by heating with a centrifuge, are used as a main raw material, and secondary materials (nitrogen source and phosphorus source) are added thereto. The inventors of the present invention have found that when culturing yeast in such a medium, various protein degradation products are added, thereby imparting freeze-freezing resistance to the yeast. Furthermore, even if the medium is in a low nutrient state that does not substantially contain molasses, it has been found that the same effect can be obtained by cultivating yeast by adding soybean protein degradation products.

That is, the present invention is based on a new finding that yeasts preliminarily cultured in a medium containing a soybean protein degradation product and other various protein degradation products have a significantly improved freezing tolerance.

That is, the present invention

1. a fermented mother for frozen dough, characterized by being pre-cultured in a medium containing a protein breakdown product,

2. The yeast for frozen dough according to 1, wherein the protein decomposition product is a decomposition product of a decomposition product of soybean protein or endo protein,

3. The yeast for frozen dough according to 1 or 2, wherein the average molecular weight of the water-soluble fraction of the protein breakdown product is in the range of 200 to 5000,

4. The yeast for frozen dough according to any one of 1 to 3, wherein the water-soluble fraction content of the protein degradation product in the medium is 0.05 to 10% by weight,

5.; frozen dough comprising yeast for frozen dough according to any one of 4 to 4, 6. Bread made using the frozen dough described in 5.

7. A method of cultivating yeast in a medium containing a protein degradation product to impart freezing tolerance to the yeast,

8. The method according to 7, wherein the protein decomposition product is a soybean protein decomposition product or an endo protein decomposition product,

Is to provide.

The invention's effect

[0006] The present invention provides a yeast having freezing tolerance. Further, by using the yeast, it is possible to provide a frozen dough having a good fermentation after freezing, and a bread having a soft and soft texture and a rich flavor made of the frozen dough. Also provided is a culture method for imparting freezing tolerance to yeast.

BEST MODE FOR CARRYING OUT THE INVENTION

[0007] The protein degradation product of the present invention includes a casein protein degradation product derived from milk, a whey protein degradation product, an endo protein degradation product, a soybean protein degradation product, and the like.

[0008] The soybean protein degradation product of the present invention is a hydrolyzed soybean protein material. Examples of the soybean protein material include isolated soybean protein, concentrated soybean protein, soy milk, defatted soy milk, whole fat soybean, Examples include defatted soybeans. Regardless of the method of hydrolysis, a conventionally known method such as acid decomposition or enzymatic decomposition can be used without particular limitation. Among them, the method of hydrolyzing with a protein degrading enzyme in an aqueous system is preferable because it can be decomposed under mild conditions with little damage to other growth promoting substances.

[0009] The enzyme used for the hydrolysis of the protein can be exoprotease or endoprotease alone or in combination, regardless of animal origin, plant origin or microbial origin. Specifically, serine protease (animal-derived trypsin, chymotrypsin, subtilisin derived from microorganisms, carboxypeptidase, etc.), thiol protease (plant-derived papain, ficin, bromelain, etc.), carboxyprotease (animal-derived pepsin) Etc.) can be used. More specifically, enzymes containing endoproteases include “Alcalase” derived from Bacillus' Rikeformis (Novozymes Japan Ltd.) and “Protin A” derived from Bacillus subtilis (manufactured by Daiwa Kasei Co., Ltd.), "Protease S" (manufactured by Amano Enzyme Ltd.), "Biolase SP_15FG" (Nagase ChemteX Corporation) (Protein AC-10) (manufactured by Daiwa Kasei Co., Ltd.), etc. are proteins that contain exo and endoproteases, such as “Protease M” and “Protea Ize 8” derived from Aspergillus oryzae. ("Amano Enzyme Co., Ltd.") and Streptomyces dariseus origin "actinase" (Kaken Pharmaceutical Co., Ltd.). In particular, the combined use of exoprotease and endoprotease makes it easy to produce a product having a desired molecular weight in a water-soluble fraction with good yield.

[0010] Hydrolysis conditions of the present invention vary depending on the type of protein hydrolase used. The amount and time of addition should be determined so that the target degradation rate is achieved in the pH range and temperature range of action of each protein-degrading enzyme. Further, when the enzyme is allowed to act after being held for 5 minutes or more, preferably 20 to 90 minutes in an alkaline region having a pH of ˜9, a high-decomposition product can be obtained efficiently in a short decomposition reaction.

[0011] As a method for producing a soybean protein degradation product using a protein-degrading enzyme, a known method can be employed. Patent Document 11 (JP-A-62-143697), Patent Document 12 (JP-A-2001-238693), Patent Document 13 (WO2005 / 089565), Patent Document 14 (Japanese Patent Laid-Open No. 2001-238693), Patent Document 15 (Japanese Patent Laid-Open Publication No. 62-014796), and the like.

[0012] Hydrolysis of a soy protein material generally produces a water-soluble fraction containing a soy protein with a low molecular weight and a water-insoluble fraction containing a relatively high molecular weight soy protein. This is not limited to soy protein materials, and the same applies to other protein materials. There are two types of soybean protein degradation products from which this water-insoluble fraction has been removed (hereinafter referred to as “separated product”) and those from which this water-insoluble fraction has not been removed (hereinafter referred to as “non-separated product”). Both can be used in the present invention, but the separated product has higher efficiency in imparting freezing tolerance. Therefore, the amount of soybean protein degradation product and various protein degradation products in the present invention added to the medium, the average molecular weight, etc. will be explained in terms of water-soluble fraction.

Yes

[0013] The average molecular weight of the water-soluble fraction of the soybean protein degradation product in the present invention is determined by removing the water-insoluble fraction by the following method. Prepare a 5% aqueous solution of soybean protein degradation product, centrifuge at 1500 xg for 20 minutes, remove the water-insoluble fraction, and then dilute 50-fold with 45% acetonitrile (0.05% TFA) To do. This was sonicated for 10 minutes and completely dissolved, and then the sample filtered through a 0.2 am filter was added to TSK gel G3000PWXL and It was subjected to gel filtration (flow rate 0.3ml / min, temperature 40 ° C, sample amount 20 波長 1, detection wavelength UV220nm) with TS gel G2500PWXL, and the weight average value obtained with GTC software was used as the average molecular weight. To do.

[0014] The average molecular weight of the water-soluble fraction of the endoprotein degradation product and milk-derived protein degradation product was determined by preparing a 0.05% aqueous solution of the protein degradation product and filtering it with a 0.45 H m filter. Use TSK gel G2000SWXL for gel filtration (flow rate 1.0 ml / min, sample amount 201, detection wavelength U V214 nm). The average molecular weight obtained by GPC software for the obtained chart is the average molecular weight.

[0015] The average molecular weight of the water-soluble fraction of the protein degradation product of the present invention is 200 to 5000, preferably 200 to 2000, and more preferably 200 to 800. In particular, yeast cultured with an average molecular weight of 200-800 in the water-soluble fraction has excellent freezing tolerance, and the frozen dough fermentation using this yeast is extremely good. When the average molecular weight of the water-soluble fraction exceeds 5000, the effect of imparting freezing tolerance decreases. On the other hand, if the average molecular weight of the water-soluble fraction is too small, it has a freezing tolerance effect but is inferior in the growth effect during yeast culture.

[0016] The yeast in the present invention may be any strain produced by means such as breeding or isolated from the natural world, regardless of the strain. For example, known yeasts, such as baker's yeast, include Saccharomyces cerpiche, which is frequently used, Saccharomyces subaum, Saccharomyces * Exhibition of Torrapola, etc. Any of these may be used.

[0017] The amount of the protein degradation product added to the yeast medium is 0.05 to 10% by weight, preferably 0.1% to 3.5% by weight, more preferably 0.2 to 2.5% by weight in the medium in terms of water-soluble fraction. Yes, if it is within this range, the effect of imparting freezing tolerance is greatly desired! /. The added amount is too small! /, And the effect of imparting freezing resistance becomes insufficient. On the other hand, if it exceeds 10% by weight, there is no problem, but the effect is small and the cost is high. The content of the water-soluble fraction in the non-separated product of the protein degradation product should be determined as the dry weight of the supernatant after removing the water-insoluble fraction by centrifuging a 5% aqueous solution (1500 xg, 20 minutes). Can do. In addition, conventionally known nutrient sources, sugar sources such as glucose that serves as an energy source for fermentation, vitamins that are fermentation-promoting substances, and inorganic substances can be added to the medium without any particular limitation. Also add other nitrogen sources such as amino acids Is also possible. Examples of the sugar source include glucose, sucrose, starch hydrolyzate, molasses, and molasses. Nitrogen sources include ammonia, ammonium chloride, ammonium sulfate, ammonium carbonate, ammonium acetate, urea, yeast extract, corn 'strip' liquor and the like. As inorganic substances, magnesium phosphate, potassium phosphate, etc. are used. As amino acids, glutamic acid, etc. are used. As vitamins, pantotensan, thiamine, etc. are used.

[0018] In an undernutrition state such as when such a nutrient source is not sufficient in the medium, particularly yeast cultured with a soybean protein degradation product or an endoprotein degradation product is excellent in freezing tolerance. The amount of soybean protein degradation product or endoprotein degradation product added to the fermentation mother's medium is 0.05 to 10% by weight, preferably 0.5% to 3.5% by weight, more preferably in the medium in terms of water-soluble fraction. It is preferably 1.5 to 2.5% by weight, and if it is within this range, the effect of imparting freezing tolerance is greatly desired. If the amount added is small, the effect of imparting freezing tolerance is insufficient. On the other hand, if it exceeds 10% by weight, there is no problem, but the difference in effect is small and the cost is high.

[0019] As a method for culturing yeast, a method for collecting bacteria, and a method for preparing yeast in the present invention, a method commonly used for yeast can be used without particular limitation. In addition, the optimum growth pH, the pH range in which it can grow, the optimum growth temperature, the temperature range in which it can grow, and the method for collecting and preparing the yeast * from the culture solution are the same as for normal yeast. Conventionally known yeast production methods can be used. The yeast obtained by culturing can be collected, washed and dehydrated to obtain the yeast of the present invention as a pressed yeast. Alternatively, it can be further dried to obtain dry yeast (dry yeast) in the form of granules, powders or granules by a conventionally known method.

[0020] (Survival rate after freezing of yeast)

The freezing tolerance of yeast in the present invention can be expressed by a predetermined survival rate of the yeast after freezing. Survival rate is expressed in terms of the survival rate of yeast after freezing storage for a certain period of time after culturing yeast in a medium containing a protein degradation product and molasses, to a stationary phase, based on the number of cells before freezing.

[0021] Specifically, shaking culture at 28 ° C and 150rpm in 100ml of medium containing waste molasses so that 0.2% protein degradation product, 0.05% by weight of potassium phosphate, and 3% sugar content Yeast cultured for 40 hours at 300 ° C in a medium of the same composition (0.2% protein degradation product and 3% molasses molasses) at 28 ° C and 150 rpm shaking for 84 hours until stationary phase Incubate. Centrifuge the yeast (5000xg , 10 minutes), collected with 10 mM potassium phosphate buffer (pH 6.5), diluted with the same buffer so that the absorbance (610 nm) is 0.1, 100 1 collected in a sample tube Store frozen at 20 ° C for 1 week. Thaw at 25 ° C, dilute with potassium phosphate buffer and plate on YP D plate to determine viability.

[0022] When the freezing tolerance of yeast is expressed in terms of the survival rate, it is 55% when cultivated with urea commonly used for culturing yeast, whereas it is cultured with the soybean protein degradation product of the present invention. More than 80% of yeast can be fermented, 75% or more of yeast cultured with the endoprotein degradation product, and 70% or more of yeast cultured with the milk protein degradation product.

[0023] (Viability after freezing of yeast cultured in undernutrition)

Similarly, the freezing tolerance of yeast cultured by adding soybean protein degradation product or endoprotein degradation product to a low-nutrient state medium that does not contain nutrient sources such as molasses is also the same as that of yeast after freezing. It can be expressed by survival rate. Viability is determined by culturing yeast in a medium containing soybean protein degradation product or yeast protein degradation product and glucose until stationary phase, and measuring the yeast survival rate after cryopreservation for a certain period of time prior to freezing. Expressed in numbers.

[0024] Specifically, seed culture was performed for 16 hours in a shaking culture at 28 ° C and 150 rpm in 3 ml of a medium containing 2.5% soybean protein degradation product or endoprotein degradation product and 2% glucose. Yeast was cultured in 50 ml of medium of the same composition (2.5% soybean protein degradation product or endoprotein degradation product and 2% dalcose) at 28 ° C, shaking culture at 150 rpm for 80 hours until stationary phase. Incubate. The fermentation mother was recovered by centrifugation (5000 xg, 10 minutes), washed with 10 mM potassium phosphate buffer (pH 6.5), and diluted with the same buffer so that the absorbance (610 mm) was 0.1. 100 1. Collect in a sample tube and store frozen at 30 ° C for 1 week. Thaw it at 25 ° C, dilute with phosphate buffered saline, and plate on a YPD plate to determine viability.

[0025] When the freezing tolerance of yeast cultured in such a low nutrient state is expressed by the above-mentioned survival rate, a Yeast Nitrogen Base without Amino Acid (hereinafter abbreviated as YNB w / oaa medium) medium commonly used for yeast cultivation. When cultivated with the soy protein degradation product, the percentage of yeast cultured with soybean protein degradation product in the present invention is 20% or more. In particular, yeast cultured with a soybean protein degradation product having an average molecular weight of 200-800 in the water-soluble fraction can have a survival rate of 50% or more, depending on the amount of degradation product added to the medium. [0026] The yeast in the present invention is useful in frozen dough that undergoes a fermentation step after the freezing step. The frozen dough includes the yeast of the present invention and is subjected to a fermentation process after freezing. The yeast in the present invention can be prepared by kneading together with various raw materials. Flour represented by wheat flour, water, fats and oils such as shortening if necessary, sugars such as sugar, glucose, fructose, liquid sugar, dairy products such as skim milk powder, milk, fermented milk, salt, eggs, yeast food, monoglyceride, etc. It is a mixture of additives such as emulsifiers, and conventionally known materials can be used as appropriate. Including bread dough, puff pastry, bun dough and pizza dough. Above all, fermentation is important, and the present invention is useful in pan dough where the demand for frozen dough is great.

[0027] The optimum addition amount of yeast to the frozen dough varies depending on various conditions such as dough composition, production method, season, and yeast cultivation conditions, but the amount needs to be increased as the freezing period becomes longer. When freezing for more than 3 months, usually 2 to 3 times the amount that is appropriate when the freezing process is not included is required. This is because yeast is damaged by freezing and many die. In addition, the yeast in the present invention does not need to be added in an amount of 2 to 3 times the usual amount as in conventional frozen bread dough. For example, in the case of using yeast cultured in a low nutrient state medium containing 2.5% or more of soybean protein degradation product having an average molecular weight of 200 to 800 in the water-soluble fraction, the yeast equivalent to the case without passing through the freezing step is used. Equivalent fermented moss is shown in the amount added. According to the present invention, the amount of yeast in the frozen dough can be reduced, which is economical and leads to a reduction in off-flavor (yeast odor) derived from yeast.

[0028] (Height after fermentation of frozen dough)

The freezing tolerance of yeast in this specification is also indicated by the fermentative power of the dough after frozen storage for a certain period. In this case, the fermented moss uses the height of the frozen dough after fermentation as an index. Divide the dough shown below into 70 g, place it in a beaker and seal it with a wrap. Store it frozen at minus 30 ° C for 1 week, thaw and ferment at 37 ° C for 3 hours, and measure the dough height.

[0029] The dough is mixed with 200g of strong flour, 10g of sugar, 4g of sodium chloride, 5g of yeast, and 124g of water. Knead for 12 minutes.

[0030] The height after fermentation of the frozen dough in the present invention measured in this way is the average of the water-soluble fraction. Depending on the culture conditions such as molecular weight and content in the medium, for example, when fermented with yeast cultured in a medium containing 2.5% or more of soybean protein degradation product in a low nutrient state, it is approximately 4 cm or more. In particular, when using yeast cultured in a medium containing a soybean protein degradation product having an average molecular weight of 200 to 800 in the water-soluble fraction, it is possible to reduce the concentration of the water-soluble fraction in the medium. It is preferable that the frozen dough has a height after fermentation of 5.5 cm or more at a weight percent or more. On the other hand, frozen dough using yeast pre-cultured with animal protein degradation products instead of soybean protein degradation products under the same conditions is generally less than 4 cm. The beaker is a so-called measuring beaker having a cylindrical outer diameter of 67 mm, and is not a Konica Leaker whose mouth is narrower than the bottom.

[0031] (Height ratio after fermentation of dough before and after freezing)

In addition, the freezing tolerance of yeast in the present invention is determined by the ratio of the height after fermentation before and after frozen storage, that is, the height after fermentation of frozen dough (cm) / the height after fermentation of dough before freezing ( cm). The dough is prepared, frozen, and fermented under the same conditions as above (height after fermentation of frozen dough), and the dough is prepared before and after freezing. Compare heights. This value also varies depending on the culture conditions. For example, when fermented with yeast cultured in a medium containing 2.5% or more of soybean protein degradation product in a low nutrient state, it is approximately 60% or more. In particular, when yeast cultured in a medium containing 2.5% or more of a soybean protein degradation product having an average molecular weight of 200 to 800 in the water-soluble fraction is used, it can be 85% or more. As the yeast of the present invention, those having high (freezing dough fermentation height) and (ratio of the dough fermentation height before and after frozen storage) are preferable in terms of freezing tolerance. is there.

[0032] (Ratio of gas generation rate of dough before and after freezing)

The freezing tolerance of yeast in this specification can also be evaluated by comparing the amount of gas generated by fermentation of dough containing the yeast before and after freezing storage. Divide the dough shown below into 20 g and leave it for 2 hours at 37 ° C, or after freezing at minus 20 ° C for 1 week, 1 hour at 22 ° C, 1 hour at 29 ° C. After thawing, ferment at 37 ° C for 2 hours, and measure the total amount of gas generated from the dough using a pharmograph (Atoichi). Shows the gas generation rate after freezing as a percentage based on the gas generation rate before freezing.

[0033] The dough is made by mixing 200 g of strong flour, 10 g of sugar, 4 g of sodium chloride, 5 g of yeast, and 124 g of water. Knead for 20 minutes using a machine (National SD-BT101).

[0034] The amount of gas generation after freezing based on the amount of gas generation before freezing from the dough thus measured varies depending on the culture conditions. For example, in the case of yeast cultured with 0.2% by weight of urea in a medium containing waste molasses Is 50%, whereas yeast cultured with 0.2% by weight or more of soybean protein degradation product, milk protein degradation product or endo protein degradation product instead of urea is almost 100%.

[0035] In the present specification, the weight of yeast is expressed as the wet weight of the culture solution after culturing and washing, by centrifuging the culture solution at 5000 xg for 10 minutes and removing the supernatant.

[0036] Examples of the bread production method include a medium seed method, a straight method, and a liquid seed method, but the present invention is not particularly limited. In addition, examples of bread types include bread, confectionery bread, special bread, and cooking bread, but are not particularly limited.

Frozen bread dough preparation methods can be broadly divided into dough ball freezing, molding freezing, and post-freezing freezing. When the frozen dough in the present invention is a frozen bread dough, any of them may be used, but the effect is particularly remarkable in the dough ball freezing method and the forming freezing method in which fermentation power after frozen storage is required. is there.

[0037] Even if the frozen dough containing yeast in the present invention does not contain a protein decomposition product, fermentation after freezing is active. That is, the yeast fermentation-promoting effect by the protein degradation product is a known force S, and the present invention is different from the yeast fermentation-promoting promotion of survival after freezing by the protein degradation product. In fact, the survival rate of yeast after freezing has been greatly improved, and its mechanism is unknown. However, pre-cultivation with protein degradation products may confer freezing tolerance to yeast.

EXAMPLES Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

<0038> <Production example of soybean protein enzyme degradation product>

Isolated soy protein (Fujipro-R Fuji Oil Co., Ltd.) 100g with 5% aqueous solution of pH7, Protin FN (Daiwa Kasei, Aspergillus oryzae origin) lg and Protin AC-10 (Daiwa Kasei, Enzymatic digestion was performed at 1.5 ° C for 5 hours at 50 ° C. Readjust this to pH7, heat at 70 ° C for 30 minutes to deactivate the enzyme, cool and centrifuge The supernatant obtained above was dried to obtain 61 g of soybean protein enzyme degradation product R. The average molecular weight of the water-soluble fraction of soybean protein enzyme digest R was 692.

Example 1

[0039] A medium of the composition shown in Table 1 containing 2.5% by weight of the soybean protein enzyme degradation product R obtained in the production example, and a baker's yeast regular strain (manufactured by Oriental Yeast Co., Ltd.) at 28 ° C and 180 rpm shaking culture. The cells were cultured for 80 hours until the yeast count reached the stationary phase. Thereafter, the yeast collected by centrifugation was washed once with a phosphate buffer, and further collected by centrifugation (5000 × g, 10 minutes). This was stored frozen at −30 ° C. for 1 week, and the survival rate after freezing of yeast was measured according to the method described above, and it was 60%.

[0040] [Table 1]

Example 2

[0041] In the same manner as in Example 1 except that a soy peptone (Nacalai Testa Co., Ltd. average molecular weight 1018 average molecular weight 1018) 2.5% by weight was used instead of soybean protein enzyme degradation product R. Thus, the survival rate after freezing of yeast was measured. The survival rate was 25%.

[0042] <Comparative Example 1>

Freeze yeast in the same manner as in Example 1 except that instead of soy protein enzyme degradation product R, YNB w / oaa medium (Difco) containing 0.67% by weight of the medium shown in Table 1 was used. Later survival was measured. The concentration of YNB w / o aa medium followed the standard usage of the product. The survival rate was 10%.

[0043] The survival rate of the yeast after freezing was 60% in the case of the soybean protein enzyme degradation product R of Production Example 1, Peptone was 25%, a value higher than that of YNB w / o aa medium. The survival rate after freezing of yeast cultured in each medium of Examples;! -2 and Comparative Example 1 is shown in FIG.

Example 3

[0044] Bread dough was prepared using the yeast cultured with the soybean protein enzyme degradation product R of Example 1. The bread dough was mixed with 200 g of strong flour (Nisshin Flour Mill Mela), 10 g of sugar, 4 g of sodium chloride, 5 g of yeast, and 124 g of water, and kneaded for 12 minutes with a kneader (Crystal Denki IMB-20T). The kneaded dough was divided into four 70g portions and placed in a beaker for wrapping. The two pieces were fermented at 37 ° C for 3 hours. The remaining two points were frozen for 1 week in a freezer at 30 ° C, then thawed at 37 ° C for 3 hours, and the fermentation of the dough before and after freezing was measured. After that, the frozen pan dough was baked for 32 minutes at 220 ° C with steam heating using Hitachi Steam Microwave Oven MRO-AX10.

Example 4

[0045] Using the yeast cultured in the medium containing soy peptone of Example 2, preparation of pan dough, measurement of fermentation power before and after freezing storage, and baking of bread dough were performed in the same manner as in Example 3.

Using yeast cultured in a medium containing the YNB w / o aa medium of Comparative Example 1 (manufactured by Difco, the nitrogen source is ammonium sulfate), the dough was prepared in the same manner as in Example 3 and fermented before and after freezing. Measurement and baking of bread were performed.

Table 2 shows the fermentation power and bread evaluation of the doughs of Examples 3 and 4 and Comparative Example 2.

[0046] [Table 2]

Example 3 Example 4 Comparative Example 2 Yeast Used Example 1 Example 2 Comparative Example 1

After fermentation of the dough before freezing

7.1 7.1 7.2

Height A (cm)

After fermentation of frozen dough

6.5 4.6 2.6

B vcm)

Dough before and after freezing

Ratio of height after fermentation of 92 65 36

(B / A * 100)

Bread after baking 〇 X

◎: Very good Solid Firm Solid bubbles are small, ○: Good size bubbles Size bubbles Hard and heavy texture

X: Defective, bread etc., bread etc.

Fresh soft fresh soft

Texture texture

[0047] By using yeast cultured in a medium containing a soybean protein enzyme degradation product as described above, fermentation after freezing was also improved. The baked bread also had a firm size of bubbles and a soft texture like bread. On the other hand, when cultured in the normal yeast nutrient medium YNB w / o aa medium, the fermented fermenter after freezing was greatly reduced compared to the case where it was not frozen. Moreover, even if this was baked, it had a hard and heavy texture due to the small bubbles. Example 5

[0048] Yeast was cultured by increasing or decreasing the content of the soybean protein enzyme degradation product R obtained in Production Example 1 in a medium of 1.5 to 3%. Yeast culture was carried out in the same manner as in Example 1. Bread dough was prepared using each yeast after culture, and fermented potatoes after freezing were measured. The composition of the bread dough, the preparation method, the dough height after fermentation of the frozen dough, and the methods for measuring the fermenting power of the dough before and after frozen storage were the same as in Example 3. Figure 2 shows the frozen dough after fermentation. As the content of soybean protein enzyme degradation product R in the medium increased, the fermentative power after freezing increased, especially when the content was 2.5% or higher, indicating a high fermenter.

Example 6

[0049] 0.2% by weight of soybean protein enzyme degradation product R obtained in Production Example, 0.05 weight of 1 potassium phosphate The survival rate after freezing of a baker's yeast regular strain (manufactured by Oriental Yeast Co., Ltd.) cultured in a medium containing 3% by weight of molasses and molasses was found to be 81%. Culture and viability were measured according to the method described above (viability after freezing of yeast).

Example 7

[0050] Endoprotein degradation product PCE80B (average molecular weight of soluble fraction 789 manufactured by Oriental Yeast Co., Ltd.) 0.2% by weight was used instead of soybean protein degradation product R in the same manner as in Example 6 except that The survival rate after freezing was measured. The survival rate was 79%.

Example 8

[0051] In place of soybean protein enzyme degradation product R, milk protein degradation product CE90M (average molecular weight of soluble fraction 535 manufactured by Oriental Yeast Co., Ltd.) was used in the same manner as in Example 6 except that 0.2% by weight was used. The survival rate after freezing was measured. The survival rate was 70%.

[0052] <Comparative Example 3>

The survival rate of the yeast after freezing was measured in the same manner as in Example 6 except that 0.2% by weight of urea was used in place of the soybean protein enzyme degradation product R. The survival rate was 50%.

The survival rate after freezing of yeast is 81% for soybean protein enzyme degradation product R, 79% for endoprotein degradation product PCE80B, and 70% for milk protein degradation product CE90M. High value was shown. The survival rate after freezing of the yeast cultured in each medium of Examples 6 to 8 and Comparative Example 3 is shown in FIG.

Example 9

[0053] Bread dough was prepared using the yeast cultured with the soybean protein enzyme degradation product R of Example 6. The bread dough was mixed with 200 g of strong flour (Nisshin Flour Mill Mela), 10 g of sugar, 4 g of sodium chloride, 5 g of yeast, and 124 g of water, and kneaded for 20 minutes with a kneader (National SD-BT101). The kneaded bread dough was divided into 20 g portions and divided into 6 parts, and 3 points were fermented at 37 ° C for 2 hours, and the total gas generation amount was measured with a farmograph (manufactured by Atoichi). The remaining 3 points were frozen in a freezer at 20 ° C for 1 week, then thawed at 22 ° C for 1 hour, 29 ° C for 1 hour, and fermented at 37 ° C for 2 hours. The amount of gas generated was measured in the same way, and the difference in the amount of gas generated before and after freezing was compared. Example 10

[0054] Using the yeast cultured in the medium containing the endoprotein degradation product of Example 7, the bread dough was prepared and the amount of gas generated before and after freezing storage was measured in the same manner as in Example 9.

Example 11

Using the yeast cultured in the medium containing the milk protein degradation product of Example 8, the bread dough was prepared and the gas generation amount before and after freezing storage was measured in the same manner as in Example 9.

Using yeast cultured in a medium containing urea of Comparative Example 3, bread dough was prepared and the amount of gas generated before and after freezing was measured in the same manner as in Example 9. Table 3 shows the gas generation amount after freezing based on the gas generation amount before freezing of the doughs of Examples 9 to 11 and Comparative Example 4.

[0056] [Table 3]

[0057] By using yeast cultured in a medium containing a protein enzyme degradation product as described above, fermentation after freezing was also improved. On the other hand, when the enzyme digestion product was not added and the culture was carried out in a medium containing urea, which is commonly used for yeast culture, the fermented fermented product after freezing was greatly reduced compared to the case where it was not frozen!

Brief Description of Drawings

[0058] [Fig. 1] Yeast survival rate after freezing

[Figure 2] Frozen dough after fermentation

[Figure 3] Survival rate after freezing of yeast

Claims

The scope of the claims

[1] A yeast for frozen dough, which is previously cultured in a medium containing a protein degradation product.

[2] The yeast for frozen dough according to claim 1, wherein the protein decomposition product is a decomposition product of soybean protein or endo protein.

[3] The yeast for frozen dough according to claim 1 or 2, having an average molecular weight of ¾00 to 5000 in the water-soluble fraction of the protein degradation product.

[4] The water-soluble fraction content of the protein degradation product in the medium is 0.05 to 10% by weight.

V. Yeast for frozen dough as described in slippage.

[5] A frozen dough comprising the yeast for frozen dough according to any one of claims;!

[6] A bread comprising the frozen dough according to claim 5.

[7] A method for imparting freezing tolerance to yeast by culturing yeast in a medium containing a protein degradation product.

8. The method according to claim 7, wherein the protein decomposition product is a soybean protein decomposition product or an endo protein decomposition product.