CS197916B1 - Semi-solid cultivating medium for the detection of microorganisms spoiling beer - Google Patents

Description

The subject of the invention is a semi-solid nutrient medium, which makes it possible to selectively determine beer-spoilage microorganisms. Of the microorganisms found in brewing, only a few spoil beer. They may be, for example, certain strains of a certain type of bacteria or yeast. These microorganisms spoil the beer at different rates, so that they are applied in spoilage depending on the amount and rate of growth in the beer.

Previous methods of microbiological control have been based on the cultivation of operational samples on specific culture media, thereby demonstrating certain groups of microorganisms. Thus it was possible to prove beer-spoiling microorganisms, but it was not possible to determine directly which of them would grow in beer the fastest. Sometimes microorganisms that did not spoil beer also grew on these soils.

In addition, some bacterial species had to be cultivated anaerobically, usually in separate containers from which air was removed and replaced with an inert gas. This was time and equipment consuming.

These disadvantages are removed by new soil. The soil consists of beer in a concentration of 20 to

99.98%, preferably 70%, and agar in a concentration of 0.02 to 0.8%, preferably 0.15%, which produces a semi-liquid consistency of the soil. Beers made from wort of varying concentrations - 10%, 12%, etc., carbonated or dehydrated beers may be used for the preparation.

197 916 carbon dioxide, for example by shaking, beers with different dissolved oxygen contents and the like.

The soil may be prepared separately and watered with the samples or, if the sample is directly beer, prepared by mixing the sample and the agar solution.

The new soil proves all kinds of microorganisms that spoil beer. For special purposes, these microorganisms may be further subdivided by addition of a suitable inhibitor to the soil.

Thus, only yeast can be detected from a mixture containing both yeast and beer-spoiling bacteria when a bacterial inhibitor such as tetracycline is added to the soil, or bacteria can be detected if a yeast inhibitor such as cycloheximide is added. Similarly, the addition of cadmium salts can suppress pediococci and detect lactobacilli.

To detect strict anaerobes, the rH of the soil is treated with a reducing agent, for example ascorbic acid, cysteine, thioglycolate, thiosulfate or sulfite.

For the separation of microorganisms according to the sensitivity to dissolved oxygen, the soil is made from beer with different dissolved oxygen content (the concentration is determined by analytical analysis.)

The exact number of microorganisms in the low cell samples is determined by membrane filtration; membrane filters with microorganisms are spilled over the new soil.

The novelty of the soil is that the soil shows only microorganisms spoiling beer, first of all those that are the fastest in beer. · It is essential to imitate the natural spoilage of beer. In addition, the soil is very cheap and simple, the detection of bacteria eliminates the cultivation in the absence of air and the detection of microorganisms is faster and easier to work than in the so far known soils. All these features are particularly suitable for use in field inspection.

The soils can be used mainly in operational microbiological laboratories of breweries, in research etc.

Example 1

Detection of microorganisms spoiling beer in bottled beer.

0.2 g of agar was stirred in 30 ml of water. The mixture was boiled in an autoclave (120 ° C, 15 min) and hot mixed with 100 ml of 12% beer. The samples were poured into the tubes, in this case the strips of membrane filters with microorganisms trapped from the beer by filtration. After cultivation (28 ° C, 4 days), the number of microorganisms was read.

Example 2

Detection of bacteria spoiling beer in samples from operation.

0.2 g of agar was stirred in 30 ml of distilled water and heated in a water bath until the agar was dissolved. The hot mixture was mixed with 100 ml of beer, previously degassed and pasteurized. Samples from brewing production, such as wort from sewers, beer from fermentation and lager vessels, etc., were poured into the test tubes in a 1 ml sample of 10 ml of soil. Cycloheximide was added to the samples prior to potting in such a quantity that the final cycloheximide concentration after potting was 0.002%. Then, the inoculated soil was cultured at 28 ° C and the number of beer-spoiling bacteria was counted on each day.

197 919

Example 3

Detection of yeasts in bottled beer.

0.7 g of agar was slurried in 100 ml of water and heated in an autoclave (120 ° C, 15 min). After cooling to 50 ° C, 3 ml of agar solution and tetracycline solution were pipetted into the test tubes in such a quantity that the final concentration after the potting of beer was 0.005% ·

After opening a bottle of 10% unpasteurized beer, 10 ml of beer was carefully aspirated by pipette and mixed with agar and tetracycline in a test tube. The soil inoculated in the test tubes was left at 5 ° C for 30 min to allow complete cooling and to achieve a semi-liquid consistency quickly. Then, the inoculated broth was cultured (28 ° C, 3 days) and the yeast count was read.

SUBJECT OF THE INVENTION

Claims (3)

SUBJECT OF THE INVENTION Semi-solid medium for the detection of beer-spoiling microorganisms, characterized in that it contains beer in a concentration of 20.0 to 99.9% and agar in a concentration of 0.02 to 0.8%. 2. The soil of claim 1, further comprising an inhibitor of certain microorganisms such as cycloheximide, tetracycline, or cadmium salts. 3. Soil according to claim 1, further comprising a reducing agent, such as ascorbic acid, cysteine, thioglycolate, thiosulphate or sulphite.