Microorganisms in food

The spoilage of foodstuffs usually involves microorganisms (bacteria, fungi and yeasts). These micro-organisms decompose the food to the point of inedibility. Sometimes food can also multiply dangerous pathogens that lead to dangerous food infections, such as salmonella. Microorganisms, which include bacteria, fungi and yeasts, are microorganisms that accompany us throughout our everyday lives. There are those with very positive effects that we exploit in food production. These include, for example, lactic acid bacteria for the production of yoghurt, yeasts for beer production and for loosening yeast dough, and molds used in the production of blue cheese and camembert. But there are also those microorganisms that are undesirable in food, as they lead to spoilage and can produce pathogenic substances. We want to take a closer look at these.


Bacterial food infections are a frequently underestimated health risk for consumers. Bacteria produce metabolic substances that can be harmful to human health. Most of them cause diarrhea and vomiting. Especially for infants, the sick and old people can lead to serious consequences. If food is contaminated with bacteria, they often multiply explosively under good growth conditions. They especially like water and heat. At lower temperatures, they grow less quickly, but they are killed by heating. Heat-sensitive bacteria usually die at a core food temperature of 70-80 ° C. Less heat-labile bacteria are killed only at temperatures above 100 ° C.

  • Preventive measures against food infections are primarily in the respect of personal and food hygiene. This includes thorough and regular hand washing before and during food preparation.
  • In particular, in the preparation of foods that may be more likely to be infected with bacteria such as poultry, eggs, meat, seafood and raw milk products, should be worked hygienically and then thoroughly cleaned all work equipment.
  • To fully cook risky products such as minced meat and poultry, ie for at least 10 minutes at 80 ° C.
  • Eat foods quickly after production or store refrigerated. Consume foods containing raw egg on the day of preparation.


Salmonellosis (= salmonella disease) is the most common food-borne infection. In particular, poultry, eggs, meat, fish and foods made from these foods may be salmonella if not or not sufficiently heated. Typical signs of salmonellosis are fever, headache, diarrhea and vomiting. These occur about 12 to 36 hours after eating the infected food and may last for several days. In adults and persons with an intact immune system, salmonellosis usually heals without complications after therapy. If elderly and immunodeficient people are affected, Salmonella infection can be fatal.


In addition to salmonellosis, a food infection by Campylobacter bacteria is important. These occur predominantly in poultry meat and internees. But also raw milk and drinking water can be contaminated. The symptoms and course of the infection are similar to the salmonella disease.

EHEC bacteria

The transmission of enterohaemorrhagic Escheria coli (EHEC) to humans occurs firstly through the consumption of contaminated foods. Here, minced meat, meat products (eg sausage, tea sausage, salami), unpasteurized milk and dairy products play a special role. On the other hand, the bacterium is transmitted from person to person due to lack of hygiene after the toilet visit. Infection manifests itself in watery diarrhea, colicky abdominal pain, cramping and vomiting.


Contamination of foods with staphylococci is usually done by humans. Staphylococci occur in the nose and throat, but also in wounds. Especially by not properly covered wounds on the hands, the bacteria get into the food. After eating these foods, diarrhea, vomiting and abdominal cramps can occur.

  • Special care should be taken when preparing food for wounds, skin rashes, throat infections and other upper respiratory tract infections.


Listeria can be found primarily in raw materials such as minced meat, raw milk and raw milk cheese. In addition, soft cheeses can be affected with red or gray mold, shrimp, mussels, oysters, lobster and fish. A health risk from Listeria exists mainly for pregnant women. An infection (= listeriosis) can lead to premature labor, miscarriage and damage to the unborn child. But listeriosis can also occur in children, immunocompromised and elderly people. It manifests itself in flu-like symptoms and may be associated with high fever and meningitis.

  • Pregnant women should refrain from consuming raw milk, raw milk products, soft cheese with red lard or noble mold, raw minced meat (eg tartare). Meat, fish and other marine animals should be sufficiently cooked before consumption.


The bacterium Clostridium botulinum produces a neurotoxin that is one of the most dangerous toxins found in nature. The disease caused by this toxin is called botulism. It can be fatal because it is a neurotoxin. Approximately 4 to 36 hours after admission, double vision, paralysis of the tongue and throat muscles and respiratory paralysis occur. Clostridia are heat resistant and toxin formation is preferably in the absence of air. Therefore, a hazard is mainly caused by canned, vacuumed and cooked foods that have not been properly sterilized. Poisoning cases are mainly known from homemade, insufficiently heated canned foods. Low-acid canned vegetables, sausage preserves, salted meats and cured ham are the most frequently affected.

  • The best prophylaxis against botulism is the proper preservation of canned or jarred foods and adequate heating of the food before serving.
  • Canned foods that show any indication that they are no longer in perfect condition, eg. As cans with Bombagen or not properly closed canning jars must be discarded.


Molds are widely known as food spoilers. Molds often infest foods such as bread and baked goods, fruits, jams, nuts, cheese, meat and sausages. Some molds produce harmful toxins (= mycotoxins). For some mycotoxins, a carcinogenic effect has been demonstrated. Molds form a network of threads in the food that is invisible to the naked eye. Mostly only the white or colored spots on the outer part of the food are visible.

  • Therefore mold-infested food should generally be discarded completely.
  • Exceptions are, for example, hard cheese with superficial onset of mold colonization and jam, which was produced with more than half of the sugar. For these foods, it is sufficient if the mold is removed over a large area.
Share with friends

Leave your comment