JPH10323180A - Yeast having high durability and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a yeast high in trehalose content, having a quality capable of being maintained for a long period, having high durability and useful for producing breads, etc., by culturing the yeast in a culture medium containing a metal ion. SOLUTION: This yeast is obtained by culturing a yeast such as a yeast belonging to the genus Saccharomyces in a culture medium containing a metal ion such as a copper ion (preferably in an amount of >=2 μg per g of a fermentable sugar in the culture medium) in an aerobic condition at a high temperature of 30-40 deg.C. A culturing pH is preferably 4.0-5.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a yeast having improved durability and a method for producing the same.

[0002]

2. Description of the Related Art Yeast, mainly pressed yeast for bread, is manufactured and sold in the form of a cake having a water content of 65 to 73%. Bread yeast is a living state that contains water,
Life activities are performed during refrigerated storage. Therefore, the activity decreases with the number of days elapsed after production, and it becomes difficult to maintain a constant quality as a yeast for bread.

Hitherto, it has been known that yeast having a high content of trehalose, which is a substance stored in cells, can maintain a constant quality for a relatively long period of time. In other words, it can be said that yeast having a high trehalose content has high durability. As a method of increasing the trehalose content in yeast, a method of increasing the culture temperature (30 ° C. to 40 ° C.) has been obtained from previous findings. However, there is a certain limit to the increase in the trehalose content due to the increase in the culture temperature.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the state of the art, and has been made so that the fermentation ability does not decrease even if the wet cake is stored in a cold state for a long period of time. The purpose is to create a highly durable yeast.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object. As a technique for further improving the durability of high durability yeast obtained by a known method,
By focusing on the addition of copper and culturing the yeast in a medium supplemented with copper, a new finding was obtained that a novel yeast having a high trehalose content and high durability could be obtained. Further, it was confirmed that the effect was further enhanced when a conventional method of increasing the culture temperature was used in combination.

The present invention has been completed as a result of further studies based on these useful new findings, and has developed a system for creating a new yeast having high durability by culturing the yeast in a metal ion-added medium. Things. Hereinafter, the present invention will be described in detail.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to carry out the present invention, yeast is cultured in a medium containing copper, manganese, zinc ions and other metal ions. The metal salt used in the present invention may be an organic compound or an inorganic compound as long as it is water-soluble and does not suppress or kill yeast growth but is efficiently taken into yeast cells. At least one metal compound can be used.

[0008] Specific metal salts include the following compounds: copper salts (copper sulfate, copper chloride, copper citrate, copper acetate,
Manganese salts (manganese sulfate, manganese acetate, manganese chloride, etc.), zinc salts (zinc sulfate, zinc acetate, etc.)
Zinc salts), magnesium salts (magnesium sulfate, magnesium acetate, magnesium chloride, magnesium hydroxide, etc.), iron salts (iron sulfate, iron acetate, iron chloride, iron oxalate,
Iron lactate, etc.) and others.

[0009] The amount of metal added is 1.5 µg or more, preferably 2 µg, per 1 g of fermentable sugar contained in the medium.
The amount is more preferably 2.5 μg or more. As the amount of sugar in the medium increases, the amount of metal added also needs to be increased, but it must be smaller than the amount that causes toxicity.

In order to produce a yeast having a high trehalose content and high durability, the yeast may be cultured in the above-mentioned metal ion-containing medium. However, if the culture temperature is increased, the trehalose content is further increased. Thus, a yeast having high durability can be obtained.

For example, the culture may be performed under the following conditions. The temperature condition is 4 to 40 ° C, preferably 33 to 35.
° C. Maintaining the temperature at a higher temperature increases the trehalose content, but when the temperature exceeds a certain temperature, growth is suppressed. The culture time is 1 to 48 hours, preferably 10 to 16 hours. Culture pH is 4-7, preferably pH 4.0.
To 5.5. These conditions are appropriately determined depending on the type and concentration of the yeast and metal salt used, and may be outside the above range in some cases.

The stirring and / or shaking conditions depend on the viscosity of the production medium, the yeast content, and the size of the fermenter, but stirring at about 100 to 1,000 rpm, or 100% for an amplitude of 12 cm, It is better to shake at ~ 200 rpm. Better results are obtained if the yeast is produced under aerobic conditions with aeration. Aeration is about 0.5 to 5 vvm, but is not limited to the main stirring conditions.

In the present invention, the yeast includes all yeasts belonging to the genus Saccharomyces, such as baker's yeast, brewer's yeast, sake yeast, and wine yeast. Non-limiting examples include, but are not limited to, yeasts of other genera: Saccharomy
ces cerevisiae, cerevisiae var.ellipsoideus,
sake, carlsbergensis, uvarum, rosei, rouxi
i other.

Further, in the present invention, various types of yeast and baker's yeast such as dry, wet, frozen and refrigerated are commercially available; yeasts for sake brewing such as Kyokai No. 7 and Kyokai 9; Various types of yeast commercially available for various uses can also be widely used.

The yeast may be produced by a conventional method.
As the medium, a liquid medium containing sweet potato molasses as a main sugar source and adding an appropriate amount of an inorganic salt such as nitrogen, phosphate, potassium or other components to the sugar source is usually used. In such a medium, yeast is produced by adding 1.5 μg or more, preferably 2 μg or more, more preferably 2.5 μg or more of metal ions per 1 g of fermentable sugar and culturing the yeast to produce yeast. In some cases, it is also possible to use an agar medium obtained by adding an appropriate amount of agar to the above-mentioned medium.

The yeast thus cultured with the addition of a metal is subjected to centrifugation, washing, dehydration, and the like to obtain cells.
If necessary, it is possible to dry the dried yeast. Hereinafter, examples of the present invention will be described.

[0017]

Example 1 Bread yeast (Nippon Sugar Beet Sugar Co., Ltd.) was added to 100 ml of a medium prepared by adding 2.7 μg of copper ion per 1 g of fermentable sugar using copper sulfate (CuSO ₄ .5H ₂ O). (Yeast) was inoculated at a dry weight of 0.1 g, and shake-cultured in a 500 ml Sakaguchi flask for 48 hours. The temperature conditions were 30 ° C. for the first 32 hours and 33 ° C. for the second 16 hours. As control groups, those in which cultivation was always carried out at 30 ° C. without addition of copper sulfate, and examples in which the first half was added at 30 ° C. for 32 hours and set to 33 ° C. for 16 hours without addition of copper sulfate were carried out. Shaking condition is amplitude 12c
m and 90 rpm.

The cells after shaking are centrifuged (3,000 rpm).
pm, 10 minutes) and washed twice with distilled water before measuring the trehalose content. The results obtained are shown in Table 1 below. In addition, the measurement of the trehalose content was carried out by extraction with trichloroacetic acid and colorimetric determination by the anthrone method.

[0019]

[Table 1]

[0020]

Example 2 To 4 L of a medium to which copper sulfate (CuSO ₄ .5H ₂ O) equivalent to 459 μg as copper ions was added, 24 g of dry yeast (regular yeast manufactured by Nippon Sugar Beet Sugar Co., Ltd.) was inoculated with a dry weight of 24 g. Aeration stirring culture was performed for 16 hours while feeding sweet molasses (fermentable sugar content: 170 g) with a 10 L jar fermenter. The temperature conditions were 30 ° C. for the first 10 hours and 33 ° C. for the last 6 hours. As control groups, those in which cultivation was always performed at 30 ° C. without addition of copper sulfate, and those in which the first 10 hours were 30 ° C. and the latter 6 hours were 33 ° C. without addition of copper sulfate were performed. Ventilation is 1v
vm, and the stirring was performed at 700 rpm.

After culturing for a predetermined time, the cells were collected by centrifugation (3,000 rpm, 10 minutes), washed twice with distilled water, and the trehalose content was measured. The results obtained are shown in Table 2 below.

[0022]

[Table 2]

[0023]

Example 3 Copper sulfate (C) equivalent to 5 g as copper ions
uSO ₄ · 5H ₂ O) was 140Kg inoculated on a dry weight the, baker's yeast (Nippontensaiseito Co. Regular yeast) to the medium 10 m ³ with the addition of, sweet potato molasses (fermentable sugar at 30 m ³ fermentor 1850kg) while feeding 1
Aeration and agitation culture was performed for 6 hours. The temperature conditions were 30 ° C. for the first 10 hours and 33 ° C. for the last 6 hours. As a control group, a culture in which culturing was always performed at 30 ° C. without addition of copper sulfate and an example in which the first 10 hours were 30 ° C. and the latter 6 hours were 33 ° C. without addition of copper sulfate were performed. Aeration was 1 vvm, and stirring was performed at 150 rpm.

After culturing for a predetermined time, the cells were collected by a continuous centrifugal separator, washed twice with chlorine-sterilized ground water, and dehydrated to obtain a pressed yeast. The results of measuring the trehalose content of the pressed yeast thus obtained are shown in Table 3 below. At the same time, the durability was investigated.
As for the durability test, first, the fabric expansion force was compared,
The degree of softening was investigated. For comparison of the dough swelling power, the pressed yeast was stored in a refrigerator for 4 weeks, and the dough swelling power before and after storage was measured. The results are shown in Table 4 below. For the examination of the degree of softening, the pressed yeast was stored at 30 ° C. for 5 days, and the degree of softening was examined. The results are shown in Table 5 below.

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

[0028]

According to the present invention, it has become possible for the first time to increase the durability of yeast by culturing the yeast in a medium supplemented with metal ions. Although the trehalose content in the yeast cells can be improved to some extent by the known temperature raising method, the effect is remarkably improved by combining with the metal ion addition method according to the present invention.

The effect is remarkable even in the result of the durability test carried out on the yeast obtained in the present invention, and after 4 weeks, a high dough expansion comparable to that on the day of production as compared with the case of no copper addition at the stage after 4 weeks Have power. On the other hand, in the case where copper is not added, it is shown that the dough swelling power is reduced during storage for 4 weeks, resulting in quality deterioration. In addition, the results of the softening test shown in Table 5 also show that the quality of the yeast is reduced.
From these results, it is clear that the baker's yeast obtained by the present invention has high durability that cannot be obtained by the conventional method. Similar effects are also obtained with other metals.

The highly durable yeast obtained by the present invention has an industrial advantage that the quality at the beginning of production can be maintained for a long period of time.

Claims (6)

[Claims] 1. A method for producing a yeast having high durability, comprising culturing yeast in a medium to which metal ions have been added. 2. The method according to claim 1, wherein a medium is used in which 2 μg or more of metal ions are added to 1 g of fermentable sugar in the medium. 3. The method according to claim 1, wherein the culture is performed at a high temperature of 30 ° C. to 40 ° C. 4. The method according to any one of claims 1 to 3, wherein the yeast is a yeast belonging to the genus Saccharomyces. 5. A yeast having a high durability, which is produced by the method according to any one of claims 1 to 4. 6. The yeast according to claim 5, which has a high trehalose content.