JPH09154562A - Removal of bacteria - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accomplish selective disinfection for various kinds of bacteria by adding a specified amount of lactic acid as a weak acid to a yeast-contg. solution contaminated with bacteria without virtually affecting the yeast itself. SOLUTION: Lactic acid is added to a yeast-contg. solution contaminated with bacteria so as to be >=0.1wt.% but <7.0wt.% (pref. 0.2-2.0)wt.% in lactic acid concentration. It is recommended that the criteria of disinfection treatment time is 20-26h or so and 30min to one hour or so for 0.1wt.% and 1wt.% in lactic acid concentration, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION Yeast is used in the production of various foods such as beer, sake, wine and other alcoholic beverages, miso, soy sauce and other seasonings, and bread. The present invention relates to a method for removing bacteria mixed in such yeast-containing foods, and more specifically, by adding lactic acid to a yeast-containing solution in which bacteria are mixed, bacteria are selectively sterilized. On how to remove.

[0002]

2. Description of the Related Art When bacteria are mixed in a yeast-containing solution, a known method for removing these bacteria is to sterilize them by adding an inorganic acid such as hydrochloric acid or phosphoric acid. However, since these inorganic acids are strong acids, it is necessary to make a delicate adjustment of the addition amount, and if the adjustment is not sufficient, there is a risk that not only bacteria but also yeast will be damaged, or the bactericidal power will be insufficient. there were. On the other hand, organic acids such as lactic acid are weak acids, and there is little risk of damaging or killing yeast. However, when sterilizing with an organic acid, the types of bacteria that can be applied are limited according to the individual organic acid, and the appropriate one is selected and recognized depending on the type of bacteria to be sterilized. There is the inconvenience of having to. Among many organic acids, lactic acid is applicable to many types of bacteria, but its influence on yeast and its adaptability when used in food have not been considered, and it is not clear how it should be used. There wasn't.

[0003]

The object of the present invention is to provide a method for removing bacteria by treating a yeast-containing solution containing bacteria with lactic acid to effectively sterilize the yeast without damaging the yeast. It is to be.

[0004]

The present invention according to claim 1 is a method for removing bacteria, which comprises adding lactic acid to a yeast-containing solution in which bacteria are mixed to sterilize the solution, and adding lactic acid to the solution at a concentration of 0. This is a method for removing bacteria, which is characterized in that it is added so as to have a concentration of 1% or more and less than 7.0%.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION There is no limitation on the yeast-containing solution to which the present invention is applied. For example, the above-mentioned beer, sake,
There are things related to alcoholic beverages such as wine, seasonings such as miso and soy sauce, and various yeast-containing foods such as bread. L- for lactic acid
There are three types of lactic acid, D-lactic acid and DL-lactic acid, but the action and effect of these are substantially the same, and any type of lactic acid can be used in the present invention. Alternatively, a single type of lactic acid may be used.
You may use it in combination of 2 or more types.

The amount of lactic acid added to the yeast-containing solution in which bacteria are mixed is suitably 0.1% or more and less than 7.0%, preferably 0.2 to 2.0%, Further, in the case of yeast powder containing bacteria, it is once brought into an aqueous solution state and then treated with lactic acid in the same manner as above. The time for sterilization treatment with lactic acid may be appropriately determined in consideration of the amount of lactic acid added, the expected amount of bacterial contamination, etc., but normally when the amount added is 0.1%, it takes about 20 to 26 hours, 0.25
% May be about 3 to 16 hours, and 1% or more may be about 30 minutes to 1 hour. If the addition amount is increased, the treatment time can be further shortened.

Next, the types of bacteria that can be sterilized and removed by the present invention are extremely large. For example, genus Bacillus such as Bacillus subtilis, Acinetobacter calcoaceticus.
aceticus), Escherichia
Escherichia coli such as Escherichia coli, Lactobacillus such as Lactobacillus brevis, and Pediococcus damnozas (Pedioco
Examples thereof include bacteria belonging to the genus Pediococcus such as ccus damnosus) and the genus Pseudomonas such as Pseudomonas fragi.

[0008]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. Example 1 35 pieces were prepared by adding 200 ml of sterile water to a 300 ml Erlenmeyer flask. The flasks were divided into 5 groups of 7 flasks each, and the brewer's yeast shown in Table 1 and 6 kinds of bacteria adjusted to a concentration of about 10 ⁴ cells / ml were added to each group, 1 ml each. Next, each group was an unadjusted one group, a group adjusted to pH 2.1 with phosphoric acid, a group adjusted to pH 2.1 with hydrochloric acid, a group containing 1% DL-lactic acid and a group containing 1% L-lactic acid. Each group was created. After stirring these with a stirrer for 1 hour, 1 ml of the mixture was taken, inoculated into an agar medium and cultured by a conventional method, and after 48 hours, the number of surviving bacteria was measured. Note that 40 ppm of acromycin was added to the medium for measuring yeast and 20 ppm of cycloheximide was added to the medium for measuring bacteria to suppress the growth of yeast and bacteria.

The results are shown in Table 1. As is clear from the table, in the case of yeast, the number of dead cells increased in those treated with phosphoric acid or hydrochloric acid as compared with the unadjusted control, but DL-lactic acid and L-
Those treated with lactic acid were not significantly different from the control, indicating that the yeast was not damaged. On the other hand, in the case of bacteria, complete eradication cannot be achieved by treatment with phosphoric acid or hydrochloric acid, but treatment with DL-lactic acid or L-lactic acid completely killed all six types of bacteria. From this, it became clear that treatment with 1% DL-lactic acid or 1% L-lactic acid for 1 hour can kill many kinds of bacteria without damaging the yeast at all.

[0010]

[Table 1]

Example 2 Muddy beer yeast 50 ml in a 300 ml Erlenmeyer flask
Twenty-five bottles each containing 150 ml of sterile water were prepared, and six flasks were divided into four groups. To each group, 1 ml of each of the 6 kinds of bacteria shown in Table 2 adjusted to a concentration of about 10 ⁸ cells / ml was added.
In addition, a bacterial solution was not added to the remaining one to serve as a control. Next, each group was 0.8 g of hydrochloric acid in addition to the untreated control group
Group adjusted to pH 2.1 with 1.2 g of phosphoric acid 1.2 g
4 groups of 50% DL-lactic acid (marketed as a food additive) were added to the group adjusted to pH 2.1 and adjusted to pH 2.1. After stirring these with a stirrer for 1 hour, 10 ⁻⁶ ml of the supernatant was cultured in an agar medium while suppressing the growth of yeast and bacteria, and the number of surviving cells was measured after 48 hours.

The results are shown in Table 2. As is clear from the table, in the method of treating with hydrochloric acid or phosphoric acid, the survival number of yeast was smaller than that of the control, and the bacteria were not completely removed. In contrast, those treated with 50% DL-lactic acid for food additives were able to completely kill and remove bacteria without damaging yeast.

[0013]

[Table 2]

Example 3 A sample similar to that of Example 2 was prepared and used for food additives.
0.25 to 4 by converting 0% DL-lactic acid into 100% lactic acid
%, And after stirring with a stirrer for 30 minutes to 18 hours, the number of surviving yeasts and the number of bacteria were measured in the same manner as in Example 2. As a result, as shown in Table 3, when the concentration of DL-lactic acid was 0.25%, treatment for 16 hours or more was required, and 1% for 1 hour and 4% for 30 minutes. ,
It has been found that bacteria can be killed and removed without damaging the yeast.

[0015]

[Table 3]

Example 4 50 ml of mud brewer's yeast was added to a 300 ml Erlenmeyer flask.
Then, 150 ml of sterile water was added thereto, and the pH was adjusted to 2.1 with hydrochloric acid, adjusted to pH 2.1 with phosphoric acid or 1% of DL-lactic acid was added thereto in the same manner as in Example 2, and the mixture was stirred for 1 hour. Then, it was suction filtered and pressed to obtain a pressed yeast. Add 9.6 g of this yeast to 2000 ml of wort and add 1
A fermentation test was performed at 0.5 ° C. for a predetermined period, and yeast activity (fermentation power) was measured from the amount of wort extract reduction. 4th result
It is shown in the table. As is clear from the table, the yeast treated with hydrochloric acid or phosphoric acid had a reduced fermentative power, but the yeast treated with lactic acid had no difference from the untreated yeast, indicating that there was no effect on the activity.

[0017]

[Table 4]

Example 5 A sample similar to that of Example 2 was prepared (however, 4 kinds of bacteria were used), and 50% DL-lactic acid for food additives was converted into 100% lactic acid to give 0.05 to 0.2. % Added, 24
Time processed. Then, the number of surviving bacteria was measured by the same method as in Example 2. The results are shown in Table 5. As is clear from the table, it can be seen that even 0.1% concentration of DL-lactic acid has sufficient bactericidal activity against various bacteria.

[0019]

[Table 5]

Example 6 A brewer's yeast-containing liquid was prepared using the same sample as in Example 5, and 10% of 50% DL-lactic acid for food additives was added thereto.
Converted to 0% lactic acid, 1.0 to 7.0% was added and treated for 30 minutes. Then, the survival status of yeasts by this treatment was examined by the same method as in Example 2. The results are shown in Table 6. As is clear from the table, the concentration of lactic acid that exerts an effective bactericidal activity with almost no effect on the yeast itself is in the range of approximately 0.1% or more and less than 7.0%.

[0021]

[Table 6]

[0022]

EFFECTS OF THE INVENTION According to the present invention, when yeast is widely used in the production of various foods and is contaminated with bacteria, treatment with lactic acid sterilizes the bacteria without damaging the yeast, Can be removed.

Claims (1)

[Claims] 1. A method for removing bacteria, which comprises adding lactic acid to a yeast-containing solution containing bacteria to sterilize the solution so that the concentration of the lactic acid in the solution is 0.1% or more and less than 7.0%. A method for removing bacteria, which comprises adding to.