Food microbiology

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Food Microbiology Laboratory, Faculty of Food Technology, Latvian Agricultural University

The Food Microbiology is a branch of microbiology and focuses on the interactions between microorganisms and food . It belongs to the system-oriented, applied sciences and, as an empirical science, has a very long history of development, beginning with the transition of human development from hunters and gatherers to settled societies with the need for the storage and appropriate preparation of food.

Microorganisms can be considered useful or harmful in connection with food. They are useful when they are used to produce food, serve as food themselves, or are used for biotechnology or food analysis. They are harmful if they spoil food or if pathogenic microorganisms are transmitted through food. The best-before date is determined using a shelf-life test.

Production of food with the help of microorganisms

Examples of foods that use microorganisms in their production:

Microorganisms as food

Examples of microorganisms that are used as food:

Microorganisms that are used as food themselves are included in the list of bacteria in food production and the list of fungi in food production in addition to microorganisms for processing food .

Food or microorganism-specific spoilage

Examples of food spoilage that is specific to certain foods or to the causing microorganisms:

Microbial food poisoning

During metabolic activity , growth and reproduction in food (and sometimes only in the intestine), some microorganisms form toxins . Examples of toxin-producing microorganisms:

  • Staphylococcus aureus and other staphylococci (gram-positive, spherical bacteria) form enterotoxins, which lead to vomiting and diarrhea after ingestion with food.
  • Clostridium botulinum (Gram-positive, endospore-forming, anaerobic bacterium, causes botulism). The botulinum toxin is one of the strongest known poisons, but because of its function as an inhibitor of nerve conduction, it has also found another use in strong dilution, namely as a "rejuvenation drug" botox .
  • Clostridium perfringens (Gram-positive, endospore-forming, anaerobic bacterium) can, in addition to its function as a causative agent of gangrene / gas burn ,alsocause gastroenteritis , whereby the toxins are only formed in the intestine during growth and spore formation.
  • Bacillus cereus (gram-positive, endospore-forming, aerobic bacterium) can produce both a vomiting toxin (in food) and a diarrhea toxin (in the intestine).
  • Some molds form toxins (so-called mycotoxins ), for example the highly liver-toxic and carcinogenic aflatoxin , ochratoxin , and patulin .
  • Poisoning of marine animals used as food by toxic algae , such as Gonyaulax catenella and G. tamarensis (Dinophyceae), or by toxin-producing bacteria

Food as a carrier of pathogenic microorganisms

Examples of pathogenic microorganisms that are transmitted through food:

bacteria
  • Salmonella species, causing diarrhea , typhoid , paratyphoid
  • Shigella species, causing dysentery
  • pathogenic strains of the intestinal bacterium Escherichia coli such as EPEC (enteropathogenic), EHEC (enterohaemorrhagic), EIEC (enteroinvasive), ETEC (enterotoxic); (the last two letters EC stand for Escherichia coli )
  • Yersinia enterocolitica , pathogen causing enteritis , etc. U. Arthritis as a long-term consequence
  • Vibrio cholerae , causing cholera
  • Vibrio eltor , causative agent of cholera-like diseases
  • Vibrio parahaemolyticus , pathogen of acute diarrhea, etc. U. Septicemia
  • Aeromonas , Plesiomonas , causative agents of gastroenteritis
  • Listeria monocytogenes , cause of meningitis , encephalitis , granulomas , miscarriages, premature births and other diseases
  • Campylobacter jejuni , the most common bacterial pathogen causing gastroenteritis , etc. U. Nerve damage from autoimmune disease ( Guillain-Barré syndrome , GBS) as a long-term consequence
Protozoa
Viruses ,

causing various diseases, especially Picorna , Reo , Arena , Arbo, Noro and Adeno viruses

Human pathogens in and on plants

Human pathogens (for example, from the faeces of wild animals) can generally penetrate plants via roots, stems, leaves, sprouts and fruits, infect them and multiply there (see also intermediate hosts ). Feeding or sucking stings by insects can also be entry points.

According to a press release from the Federal Institute for Risk Assessment (BfR), watermelons stored for a long time can transmit dangerous pathogens such as salmonella , listeria or EHEC (enterohaemorrhagic Escherichia coli). If the outer shell is contaminated with pathogens during production, transport or storage, these pathogens can infect the low-acid pulp when cut open and will multiply relatively quickly if stored too warm or too long. “To protect against infection, consumers should therefore eat pre-cut melons quickly or refrigerate them.” Pregnant women, small children, old and sick people should avoid eating cut melons that have been kept at room temperature for several hours as a precaution.

In 2011, at least 147 people in the United States contracted Listeria monocytogenes after consuming contaminated cantaloupe , 33 deaths and a pregnant woman miscarriage. Consumption of imported watermelons in late 2011 triggered a salmonella outbreak in Germany, the UK and Ireland.

Measures against harmful effects of microorganisms

Examples of preventing or delaying microbial spoilage of food:

  • Sterilization by heating, for example canned food
  • Reduction of the microorganism concentration by heating ( pasteurization and similar processes)
  • Killing all microorganisms or reducing the microorganism concentration by exposure to gamma radiation , ultraviolet radiation
  • Preservation by cooling
  • Preservation by drying (lowering the water activity )
  • Preservation through salts (lowering the water activity)
  • Preservation by acidification (partly with the help of bacteria)
  • Preservation by smoking
  • Preservation by adding preservatives that inhibit the activity of microorganisms or even kill them

Measures to prevent the contamination of food with pathogenic, toxic or food-spoiling microorganisms:

  • Cleanliness in the production and processing of food
  • Keep away from sources of contamination
  • Personal hygiene
  • Cleaning and disinfection of rooms and devices

literature

  • Johannes Krämer, Alexander Prange: Food Microbiology , 7th edition, UTB Uni-Taschenbücher 1421, 2016, ISBN 978-3-8252-4658-7
  • James M Jay, Martin J. Loessner, David A. Golden: "Modern Food Microbiology", 7th edition, Springer Verlag, 2005, ISBN 0-387-23180-3
  • Gunther Müller, Herbert Weber: Microbiology of Food - Basics , 8th edition. Behr's Verlag, Hamburg, 1996, ISBN 3-86022-209-0
  • Thomas J. Montville, Karl R. Matthews: Food microbiology: an introduction , ASM Press, Washington DC, 2004, ISBN 1-55581-308-9
  • Michael P. Doyle, Larry R. Beuchat, Thomas J. Montville, Karl R. Matthews: Food microbiology: fundamentals and frontiers , ASM Press, Washington DC, 2001, ISBN 1-55581-208-2
  • W. Holzapfel: Lexicon of food microbiology and hygiene , 3rd edition, Behr's Verlag, Hamburg, 2004, ISBN 3-89947-048-6
  • Jürgen Baumgart (Hrsg.) Et al. Authors: Microbiological analysis of food , 3rd edition Behr's Verlag, Hamburg, 1993, ISBN 3-86022-114-0
  • Heribert Keweloh: Microorganisms in Food , 2nd edition, Pfanneberg-Verlag, Haan-Gruiten, 2008, ISBN 3-8057-0527-1

Individual evidence

  1. ↑ Irene Esteban Cuesta: Investigations on the endogenous microbial contamination of melons (Cucumis Melo) , Department of Veterinary Science at the Faculty of Veterinary Medicine at the Ludwig Maximilians University in Munich, Chair for Food Safety, Munich 2016, PDF file
  2. ↑ a b c d Melons can transmit pathogenic germs , August 9, 2013