JPH09234058A - New yeast and production of bread containing the yeast - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dough not only rich in sugar, oil and fat but having excellent resistance against freezing even in the case of a lean dough for a loaf of bread and French bread by containing at yeast having resistance against freezing and capable of accumulating a specific amino acid in mycelia. SOLUTION: This dough for bread contains a yeast resistant to freezing and capable of accumulating >=1 amino acids selected from proline, arginine, lysine and glutamine, e.g. Saccharomyces cerevisiae AJ14704 (FERM P-15494) or Saccharomyces cerevisiae AJ14705 (FERM P-15495). It is preferable to select cells which accumulate larger amount of the above amino acids than the mother cells by treating to mutagenize the mother cells.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel yeast excellent in freezing resistance and a method for producing bread containing the yeast.

[0002]

2. Description of the Related Art In recent years, in the bakery industry, the use of frozen bread dough has become popular in order to streamline the process by labor saving and to provide freshly baked bread that meets the needs of consumers. Normal baker's yeast having no freezing tolerance is often damaged by freezing due to fermentation before freezing, resulting in death or deterioration of fermentation ability, and in many cases bread of good quality cannot be obtained. It is known that freezing dough is particularly serious when using a lean dough, and it is necessary to shorten the fermentation time before freezing or to increase the amount of yeast, which tends to result in a bad bread lacking flavor. Therefore, frozen dough is often applied to rich bread.

Saccharomyces rosei (Japanese Patent Publication No. 59-25584) and Saccharomyces cerevisiae FTY (FRY-413) are used as baker's yeast having excellent freezing tolerance.
(Japanese Patent Publication No. 59-48607), Saccharomyces cerevisiae IAM 4724 (Japanese Patent Publication No. 63-58536),
Saccharomyces cerevisiae FTY-3 (Tokuhei 4-2
0595), Saccharomyces cerevisiae KYF (Japanese Examined Patent Publication No. 6-87772) and the like are known, but the current situation is that the above problems have not been sufficiently solved.

[0004]

[Problems to be Solved by the Invention] A yeast having excellent freezing resistance was developed not only in a rich dough containing a lot of sugars and fats and oils but also in a lean dough for bread and French bread, and frozen using the yeast. The purpose is to examine a method of making bread dough and bread.

[0005]

As a result of intensive studies to solve the above problems, the present inventors have found that some amino acids known as cryoprotectants, such as proline, arginine, lysine, and glutamic acid, are used. It was found that a yeast suitable for frozen storage can be obtained by obtaining yeast that accumulates in a large amount in the cells, and that by using this, bread dough with high freezing resistance can be obtained.

[0006] That is, the present invention uses a yeast having freezing resistance in which one or more kinds of amino acids among proline, arginine, lysine, and glutamic acid are accumulated in the cells, and a bread dough characterized by using the yeast. It relates to a method for producing bread.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In order to obtain a yeast according to the present invention which accumulates a specific amino acid in a bacterial cell, a method of inducing by mutation treatment or a method of accumulating an amino acid in the bacterial cell by an enzymatic reaction of the yeast itself is used. it can. Any yeast can be used as long as it can be used as baker's yeast, and for example, Saccharomyces cerevisiae, Saccharomyces ubalm, Saccharomyces chevalier, Saccharomyces rosei and the like can be used, and those belonging to Saccharomyces cerevisiae are particularly preferable. The baker's yeasts other than Saccharomyces, such as the genus Torluspora (for example, Torluspora del Brutuki) and the genus Kluveromyces (for example, Kluveromyces thermotolerance), are also applicable as parent strains of the present invention.

In the present invention, a mutant strain obtained by subjecting the above-mentioned parent strain to a mutagenesis treatment or a strain in which the number of specific amino acids in the cells is increased by the enzymatic reaction of yeast is selected and used.

As the mutagenesis treatment, a method of selecting yeast resistant to the proline analog is advantageous. Examples of the analog agent include thioproline, azetidine-2-carboxylate, dehydroproline and the like, but any proline analog may be used.

As the treatment for mutagenesis, agents such as ultraviolet irradiation, irradiation, ethane methane sulfonate (hereinafter abbreviated as EMS), N-methyl-'N-nitro-N-nitrosoguanidine and the like can be used.

As the method using the enzyme reaction of yeast, a method of adding a precursor of a specific amino acid to a medium and accumulating the specific amino acid in the cells can be used in addition to the carbon source necessary for yeast growth. For example, in the case of lysine, L-α-aminoadipic acid can be added to the medium to accumulate lysine in the cells. In order to accumulate the specific amino acid in the bacterial cells, it is particularly effective to make the degrading ability of the specific amino acid in the strain breeding process.

[0012]

Embodiments of the present invention will be described below.

[0013]

Example 1 To obtain a mutant strain having resistance to proline analog, Saccharomyces cerevisiae AJ-14707 (hereinafter referred to as AJ 14707 strain), which is a proline-degrading strain-deficient strain, is obtained.
It was achieved by carrying out a mutation treatment using EMS as a parent strain.

Strains deficient in the proline-degrading system are J. Bacteriology,
140, 498-503 (1979), J. Bacteriology, 140, 504-507 (1
It can be obtained according to (979). That is, Saccharomyces cerevisiae was treated with EMS, grown in a medium containing galactose and glutamic acid, and a strain that did not grow in a medium containing galactose and proline was selected. It is AJ 14707.

YPD agar medium (polypeptone 2.0%,
Yeast extract 1.0%, glucose 2.0%, agar 1.5
%) At 30 ° C., and suspended in 3ml 48 hr cultured AJ 14707 strain 0.1M potassium phosphate buffer to the cells in 4 × 10 ^-7 cells / ml of (pH 7.0), 0. 1m
1 EMS was added, and a mutation treatment was performed at 30 ° C. for 20 minutes.
Then, the EMS was neutralized with 6.0% sodium thiosulfate, and the cells were washed. The washed cells are appropriately diluted, and a minimal agar medium containing 5 mg / ml of azetidine-2-carboxylate (manufactured by Difco, 0.67% of Bacto yeast nitrogen base, 2% of glucose and agar 1.
5%) and cultivated at 30 ° C. for 7 days, and picked up growing colonies.

The above colonies were further added to a minimal medium (Bacto yeast nitrogen base 0.67 manufactured by Difco).
%, Glucose 2%), cultivated at 30 ° C for 2 days, harvested cells, extracted with hot water (100 ° C, 15 minutes), measured the amino acids in the cells with an amino acid analyzer, and have a high proline or arginine content. As AJ 14704 and respectively
Acquired AJ 14705 shares. These two strains were transferred to FERM P-15494 and FERM P-1 at the Institute of Biotechnology, Institute of Industrial Technology, respectively.
Deposited as 5495.

[0017]

[Example 2] Saccharomyces cerevisiae transferred from East Genetic Stock Center, USA
X2180-18 (available freely to any number of people, below X2180-
Applied Microbiology, 9, 1 (19 strains)
According to the method of 61), various concentrations (0-0.5%) of L-α-aminoadipic acid were added to the culture solution, and the intracellular lysine content was about 0%, 1% with respect to the dry cell weight, 2%, 5%, 10%
Strains were created.

[0018]

[Example 3] AJ 14707 strain and AJ 147 obtained in Example 1
Table 1 shows the results of comparing the freezing tolerance of the 04 strain and the AJ 14705 strain. The above strain was cultured in a minimal medium at 30 ° C. for 2 days, stored at −20 ° C. for 7 days, and the viability was calculated by measuring the viable cell count before and after storage on a YPD agar medium.

[0019]

[Table 1]

As is clear from these results, AJ 14704
The strains AJ 14705 and AJ 14705 had an intracellular proline amount increased by about 10 to 20 times and the survival rate increased by about 6 to 9 times compared with the AJ 14707 strain. Furthermore, regarding the AJ 14705 strain, the intracellular arginine amount was about twice that of the parent strain.

[0021]

[Example 4] The results of comparing the freeze resistance of the strain prepared in Example 2 by the same method as in Example 3 are shown in Table 2.

[0022]

[Table 2]

As is clear from these results, the freeze resistance was increased by increasing the lysine in the cells.

[0024]

Example 5 As frozen baker's yeast, AJ 14704 strain and AJ 14705 strain which are high proline accumulation strains or high arginine accumulation strains.
Bread dough was prepared using two strains and a high-lysine strain in which intracellular lysine was about 5% and 10% with respect to dry bacterial cells. The bread dough composition is shown in Table 3. As controls, AJ 14707 strain, X2180-18 strain and commercial yeast Asahi Kasei 45 strain were used.

[0025]

[Table 3]

With respect to the bread dough prepared as described above, the freezing resistance of the bread dough was examined by the following method.

(Frozen section) Bread dough was dispensed on a 24-well plastic plate and immediately pre-fermented at 30 ° C for 1 hour. The plate was wrapped in aluminum foil and frozen and stored at -20 ° C for 7 days. Fermentation was carried out for 2 hours with Fermograph SS (manufactured by ATTO), and the amount of carbon dioxide was measured.

(Non-frozen section) After the dough was dispensed on a 24-well plastic plate, it was immediately fermented for 3 hours on a Thermograph SS to measure the amount of carbon dioxide.

Table 4 shows the freezing tolerance of the high proline accumulating strain, the high arginine accumulating strain, the high lysine accumulating strain and the control strain. The degree of freezing resistance was expressed as a percentage of the amount of carbon dioxide gas produced in the three-hour fermentation in the frozen region relative to the amount of carbon dioxide gas produced in the three-hour fermentation in the non-frozen region.

[0030]

[Table 4]

As is clear from Table 4, the bread dough prepared using the high proline-accumulating strain or the high arginine-accumulating strain and the high lysine-accumulating strain had better freezing tolerance than the bread dough prepared using the control strain.

[0032]

Example 6 A frozen bread dough was prepared using the high proline-accumulating strain or the high arginine-accumulating strain and the high lysine-accumulating strain used in Example 5. The composition and process are shown below.

Blending: Wheat flour (strong flour) 100.0 g Salt 2.0 g Malt double dilution 0.4 g Yeast 2.0 g Dough improving agent (manufactured by Asahi Foods) 1.0 g Water 65.0 g

Process: Mixing L8M3 Kneading temperature 25 ° C Floor time 28 ° C, 75%, 30 minutes Bench time 20 minutes

After molding the prepared bread dough, -20 ° C
For one week. After that, the product was thawed at 20 ° C., proofed at 70 ° C. at a humidity of 70% for 70 minutes, and then baked at 210 ° C. for 17 minutes.

[0036]

Industrial Applicability According to the method of the present invention, frozen bread dough having excellent fermenting ability after frozen storage can be produced, and particularly, even in a lean dough, freezing resistance is excellent, so that it is industrially used. It is of high value.

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Claims (8)

[Claims] 1. A yeast having freeze-tolerance, which accumulates one or more amino acids selected from proline, arginine, lysine, or glutamic acid in the cells. 2. The yeast belongs to the genus Saccharomyces.
The yeast described. 3. The yeast according to claim 2, wherein the yeast is Saccharomyces cerevisiae. 4. The yeast is Saccharomyces cerevisiae AJ 1
The yeast according to claim 3, which is 4704 (FERM P-15494) or Saccharomyces cerevisiae AJ 14705 (FERM P-15495). 5. A dough containing the yeast according to claim 1. 6. The dough according to claim 5, which is a frozen dough. 7. A bread containing the yeast according to claim 1. 8. A method for producing bread, which comprises fermenting the yeast according to any one of claims 1 to 4.