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31st July 2019  Content supplied by: R-Biopharm AG

On The Trail of Beer Spoilage Bacteria

In general, beer is not a likely habitat for microorganisms: the alcohol content, the low pH value, the anaerobic atmosphere, the hop bitters and the limited nutrient supply make beer a rather hostile environment. However, some bacteria have adapted to this environment.

Although not being pathogenic, the microorganisms can cause undesirable odor and off-flavor as well as turbidity in beer. Three categories of beer spoilers can be distinguished: Obligate beer spoilage bacteria (e.g. Lactobacillus brevis, Pediococcus damnosus, Megasphaera spp., Pectinatus spp.) will always cause spoilage. Potential beer spoilage organisms (some lactic acid bacteria, exogenous yeast) will only grow under certain conditions, e.g. in the case of low alcohol or hop content. Indirect beer spoilage microorganisms cannot grow in beer, but may be contained in the used raw materials. The following table gives an overview of beer spoilage microorganisms and the off-flavors they cause.

Micro-organism Off-flavour

Exogenous yeast (e.g. Saccharomyces diastaticus)

Flowery or bitter taste

Lactic acid bacteria (e.g. Lactobacillus brevis)

Sour taste
Acetic acid bacteria Taste of vinegar
Thermophilic bacteria Taste of vegetables or celery

Pediococci (e.g. Pediococcus damnosus)

Buttery taste

Firmicutes (Megasphaera spp., Pectinatus spp.)

Taste of rotten eggs
Molds Moldy taste


Microbiological analysis of beer

To provide a flawless product, breweries have to carry out a thorough quality control and test their beer for various contaminants. This is often challenging, especially for small breweries. With the traditional microbiological detection method requiring enrichment in culture media for several days, the analysis procedure often impedes production processes. As a faster alternative, PCR tests that provide results within a few hours are becoming increasingly important. This molecular biological method is not only highly specific but also very easy to perform when using the modern GEN-IAL® test kits. Without enrichment, these PCR tests can be used for the analysis of raw materials, in-process samples from production and filling as well as for end products.

Further information:


R-Biopharm portfolio for beer analysis


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Date Published: 31st July 2019

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