DE1673280C3 - Method for the microbiological detection of beer spoiling pediococci - Google Patents

Description

The invention relates to a method for microbiological, selective detection of beer spoiling pediococci using an Actidion and Solid nutrient medium containing sodium acetate on the basis of half-evaporated hops Beer with anaerobic incubation.

The production of beer takes place almost exclusively under conditions that are not absolutely infection-free, see above that various microorganisms occur in beer and in the intermediate products of beer production and can develop. While most of the microorganisms in varying amounts appear only as harmless accompanying flora, only a few germs are real beer spoilers known. Among these are the beer pediococci (Pediococcus cerevisiae), also called "beer sarcines", the most dangerous infectious agents. You can in the raw materials, in the intermediate products and can be found in the finished beer, where they are caused by cloudiness and changes in taste cause severe damage and make the beer inedible for human consumption. The capture Already minor infections from beer diococci in the context of the brewery biological control is therefore a key problem.

Since the microscopic control of the analysis samples is completely inadequate, various proposed microbiological analysis methods that allow a higher accuracy of detection. The nutrient substrates used for this are essentially based on beer wort or beer. These are: ammoniacal wort, pasteurized beer, cloudy beer, activated charcoal beer, neutralized beer, yeast water. It is exclusively about liquid nutrient substrates. The incubation the inoculated nutrient solutions must be done in the absence of air, since the beer pediococci are anaerobic Bacteria are. The incubation temperature is around 25 ° C.

Insofar as these substrates are largely unchanged beer (e.g. pasteurized beer), although they show a high selectivity for the detection of beer pediococci. The analysis time is for However, modern concerns of operational monitoring are considerably too long (10 to 18 days) and the accuracy of the verification too low. Traces of infections are not recorded. Are additives for the substrates Analysis time shortened (neutralization with ammonia, addition of activated carbon, addition yeast extract, cloudy beer, etc.), the analysis time can be shortened to 6 to 10 days; the high selectivity is reduced, however, so that non-specific, non-beer-spoiling germs for Development can come.

It should also be noted that the nutrient substrates described above are not suitable for the biological analysis of all in The raw materials, intermediate products and the finished beer from the brewery are used be able; Rather, they are essentially only focused on the investigation of the cultivated and pitching yeasts switched off. Quantitative analyzes are not possible at all with the analysis substrates that have been used up to now possible.

A further development is the use of a solid nutrient substrate, the "WL" -Dillerential-Medium " This known substrate is a nutrient agar that is not on the Base of wort or beer builds up; it is a semi-synthetic nutrient medium which, through the addition of antibiotics Actidion enables the bacteria to develop selectively. The breeding ground is for operational control the fermentation industry and can also be used for quantitative and qualitative evidence the beer pediococci are used in the pitching yeast of the brewery. The biological Analysis of other brewery samples is, however, very uncertain, as either the beer pediococci does not grow or an unspecific Bcglcitllora the detection of the actual beer spoiling germs covered.

The invention was based on the object of a method for microbiological, selective detection beer spoiling pediococci using a solid containing Actidion and sodium acetate To find nutrient substrates that enable accurate, rapid and selective detection of even minor infections, including traces of beer pediococci.

This problem was solved by a method for the microbiological, selective detection of beer spoilage Pediococci using a solid containing Actidion and sodium acetate Nutrient substrate on the basis of half-evaporated, hopped beer with anaerobic incubation, characterized in that the nutrient substrate per liter of 0.05 to 0.4 g of sodium acetate and 0.01 to 0.1% polyoxyethylene sorbitan monooleate and after sterilization before casting the plates 0.2 to 0.4% / i-Phenylethyl alcohol can be added.

The method according to the invention allows reliable and rapid, qualitative and quantitative acquisition the beer pediococci in all analysis samples from the brewery. The goal was a duration of analysis Aimed for 2 to 6 days. The nutrient substrate according to the invention is characterized by its Structure on the basis of half-evaporated, hopped beer with the addition of substances on the one hand, that promote the development of beer sarins, and on the other hand of selectively acting substances that suppress the unspecific floating flora. At first, components became more common bacteriological culture media used, the combination of which promotes the detection of the Bicr-Pcdiococci. However, since different types of bacteria can grow on this basic substrate, additive

the substances listed below enable the selective development of beer pediococci:

1. Addition of sodium acetate, a special growth factor for lactic acid bacteria (the Pcdiococci belong to the lactic acid bacteria);

2. Addition of soluble starch and gelatin; both have a beneficial effect on development from pediococci;

3. Addition of polyoxyethylene sorbitan monooleate, a wetting agent that increases the absorption of the substance Promotes microorganisms;

4. Addition of liver extract to inhibit the accompanying aerobic flora;

5. Addition of bromocresol green, an indicator dye that turns yellow with an acid reaction and makes it easier to identify the developing colonies of microorganisms;

6. Addition of Actidion, an antibiotic that prevents yeast growth;

7. Addition of / J-phenylethyl alcohol, a higher one Alcohol, which inhibits the growth of most bacteria, the beer pediococci in the specified concentrations, however, not affected.

Nutrient composition

10% hopped wort becomes bottom-fermented Brewer's yeast fermented (25 ^ C), the yeast filtered off and the filtrate reduced by half by boiling. ml of substrate is made up to ml with distilled water and filtered through kieselguhr. In addition to give

Yeast extract (Difco) 10g

Maltose 10 g

Casamino acids (Difco) 10 g

Liver extract (Difco) 10 g

Agar 20 g

Then it is made up to 1000 ml with distilled water and adjusted to pH 6.5. Then come the further additions:

Polyoxyethylene sorbitan monoleate · · 0.2 ml

Gelatin 4 g

Soluble starch Ig

Sodium acetate 0.1 g

MgSO ₄ 0.1g

CaCl ₂ 0.2 g

Bromocresol Green 0.02 g

Actidion solution

(200 ml Actidion to 100 H..O) .... 2 ml

12 per cent. Hopped wort ... '. 100 ml

The culture medium is sterilized at 120 ° C. for 15 minutes. Before the plates are poured, the culture medium 0.3 "/ 0 / i-phenylethyl alcohol added.

The analysis samples to be examined can either be spread directly on the nutrient medium or brought to the culture medium using membrane filters. With a subsequent 2-to Every day anaerobic incubation at 25 ° C selectively develops the beer pediococci in small ones white colonies on the agar surface. The quantitative analysis does not present any difficulties.

The nutrient medium was in the context of the brewery biological Operational analysis with all analysis samples in the brewery checked and proven are very well suited for the reliable and quick detection of beer spoiling pediococci. What was new and surprising about the findings was that, depending on the analysis sample, reliable results in 2 to 6 days have been obtained, and that the new nutrient substrate with good success in all brewing biology Analyzes can be used to detect evidence of beer pediococci.

The increasing rationalization and intensification of the brewing process demands an ever more intensive one biological monitoring of the farm. The development of the nutrient medium according to the invention is therefore of particular importance, since it can detect even small traces of pediococcal infections allows the analysis time to be shortened considerably compared to older methods can. The universal application contributes to a considerable security and simplification of the Work in the brewery biology company laboratory.

Claims (1)

'L Claim: Method for the microbiological, selective detection of beer spoiling pediococci using a solid nutrient substrate containing Actidion and sodium acetate on the basis of half-evaporated, hopped beer with anaerobic incubation, characterized in, that the nutrient substrate per liter of 0.05 to 0.4 g of sodium acetate and 0.01 to 0.1% Polyoxyethylene sorbitan monooleate and after sterilization before casting the plates 0.2 to 0.4% / i-Phenylethyl alcohol can be added. »5