Microbiology in food and animal feeds

Our microbiological laboratory supports customers from the food and feed industry in the quality control of their products. Our services cover a wide range of product groups in the food industry. In addition, we also carry out microbiological tests on:

  • raw materials in food production,
  • drinking water,
  • packaging materials,
  • drinking water and animal feed.

The analyses are carried out according to recognised methods (ASU §64 LFGB, DIN/EN/ISO, European Pharmacopoeia). In addition to classical (cultural) methods, modern techniques such as ELISA and PCR can also be applied.

Microbiological service spectrum

Determination of pathogenic microorganisms

The main focus of the food business operator's own control with regard to food safety should always be on the exclusion of pathogens and compliance with the corresponding limit values laid down in European and national food law.

With regard to this consumer protection measure, we offer, among other things, tests for the detection and/or counting of the following germs with pathogenic properties:

  • Bacillus cereus
  • Thermophilic Campylobacter (C. jejuni, C. coli)
  • Clostridium perfringens
  • Enterohaemorrhagic (EHEC) and Shiga toxin producing (STEC) Escherichia coli
  • Listeria monocytogenes
  • Staphylococcus aureus
  • salmonella enteritidis
  • Yersinia enterocolitica

In this context, it is also possible to detect increased antibiotic resistance in certain microorganisms: MRSA (methicillin-resistant Staphylococcus aureus) and ESBL (Extended Spectrum ß-lactamase positive bacteria).

The detection or exclusion of further pathogens is possible on request. 

Health effects

The presence of the abovementioned bacteria in foodstuffs may cause foodborne infections and intoxications in the consumer after consumption of these products:

When food is infected, pathogenic microorganisms enter the gastrointestinal tract with the food, adhere there, multiply and penetrate into the cells. Finally, after an incubation period of varying lengths, they cause symptoms of disease which are based on damage caused by the pathogen itself or on excessive defensive reactions of the human organism.

Health damage caused by toxins produced by pathogenic germs is known as intoxication. Bacterial toxins are often proteins or their building blocks which become active in the intestinal tract. This is also referred to as enterotoxins. Mostly these toxins are already formed in the food during the multiplication of the germs. To trigger the disease, it is sufficient to eat the food containing the toxin, while the absorption of living cells of the pathogen is not absolutely necessary. 

Rapid analysis

For the detection of Salmonella, EHEC/STEC and Listeria monocytogenes a rapid analysis within 24h can be offered on request. The very sensitive analysis is performed using molecular biological methods (PCR), whereby the DNA of the pathogens is detected.

Determination of indicator germs

Foods are always described as spoiled if they have become unusable for human consumption due to adverse changes. These adverse changes also include the proliferation and metabolic activity of microorganisms. Often, but not necessarily, these processes are accompanied by sensory changes such as discoloration, gas formation and bombardment, rot, acidification or fermentation.

Responsible for spoilage are often microorganisms that are grouped. We are happy to investigate the following:

  • Milk and acetic acid bacteria
  • Yeasts and moulds
  • pseudomonads
  • enterobacteria
  • aerobic (bacilli) and anaerobic (clostridia) spore formers

In food analysis, indicator germs ("indicator microorganisms") are also used to critically examine process hygiene or to detect contaminations and their possible origin. Indicators for this could be the following:

  • lack of product heating: Enterobacteria
  • lack of packaging hygiene: lactic acid bacteria
  • lack of personal hygiene: staphylococci and/or lactic acid bacteria
  • fecal impurities: Escherichia coli and faecal coliforms (thermotolerant coliform germs), enterococci or enterobacteria (mainly in animal foodstuffs)
  • Soil contamination, environmental contact: Clostridia and/or enterobacteria (mainly in vegetable foods)

The detection of indicator germs that indicate hygiene deficiencies in the manufacturing process or the presence of a certain number of these microorganisms in the product may require further testing and/or countermeasures in accordance with food law requirements.

Investigation of technologically desirable microorganisms

In the production of food, the desired microorganisms must also be mentioned, which are present as natural flora or are also used in the form of starter cultures or technological additives and which are required for certain product-typical ripening and refinement steps. Examples are

  • fermentatively effective lactic acid formers (lactobacilli, micrococci)

in dairy products such as yoghurt and cheese, in raw sausage or ham, in sauerkraut and in probiotic products for dietary food supplements for humans and animals.

Further applications are

  • Cultures of noble moulds on certain types of sausage and cheese.

In some cases yeasts are also regarded as desired microorganisms, for example during the ripening of air-dried raw cured products. The use of

  • Baker's yeast and wine yeast

can be regarded as one of the oldest biotechnologies.

After consultation, the exact species determination of a bacterial or fungal isolate obtained during food testing can be carried out in individual cases. This is achieved by biochemical, molecular biological and/or mass spectrometric follow-up analyses.

1. Environmental monitoring

Environmental monitoring determines the surface germ content of work surfaces and tools (cleaned and/or disinfected or during production) as well as the air germ content. The following methods are available for investigation:

  • Impression samples, primarily for larger, flat, solid surfaces
  • Swab samples for all surfaces and tools with quantitative (germs per cm²) or semi-quantitative evaluation (0.1-10; 11-100; >100 germs per sampled area)
  • Trapping plates (trays with a solid culture medium which are left open in the production plant for a certain period of time in order to measure the airborne germ content)
  • Airborne germ measurement with special collection devices

All necessary materials for sampling will be provided by us. Sampling can also be carried out by one of our trained employees.

2. Personnel hygiene

In order to prevent one of the main entry routes of germs into the food production process, regular hygiene training of employees is recommended as well as their control in sensitive production areas. The following tests are suitable for this purpose:

  • Swab on hands and/or work clothing to check that cleaning is adequate.
  • Stool examinations to exclude diseases or to detect clinically inconspicuous permanent excretors

The materials required for sampling are also provided by us.

1. Feed microbiology

Following points for farm animal feeds (e.g. in the context of QS feed monitoring) are important:

  • the detection of salmonella,
  • the exclusion of antibiotic performance enhancers (inhibitor test) or
  • estimation of contamination with yeasts, moulds and clostridia

In order to assess the general hygiene status of feed, testing may be extended to enterobacteria, E. coli and other germs, in particular for pets.

2. Assessment of stable hygiene

For the control of hygiene management in livestock production as so-called primary production for food, special tests are urgently recommended from our experience. These include among others

  • the examination of the cleaning and disinfection of stable facilities before new installation/reoccupation,
  • sampling of purchased animals to exclude disease vectors; and
  • direct pathogen detection within the framework of legal requirements, e.g. prior to poultry slaughter (faeces, sock swabs).

If the results are positive, effective countermeasures can be taken quickly and specifically.

For more information

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Related topics

  • Minimum durability studies
  • Rapid analysis