Bacteria In Food

Alexander Bruni
Author: Alexander Bruni Time for reading: ~7 minutes Last Updated: November 06, 2022
Bacteria In Food

Bacteria found in food can be both useful for the body and pathogenic - which usually cause food poisoning of varying severity. Beneficial bacteria include probiotics (lacto- and bifidobacteria) and prebiotics. They are mainly found in fermented milk products. Beneficial bacteria stimulate and normalize digestion and metabolic processes in the body,

Bacteria contained in food can be divided into two groups:

  • Beneficial bacteria , which provide normal intestinal microflora, are mainly found in fermented milk products.
  • Harmful - bacteria that cause food spoilage and, as a result, food poisoning.

Beneficial bacteria

Beneficial bacteria include:

  • Probiotics (lactobacteria, bifidobacteria).
  • Prebiotics.

Probiotics are useful bacteria for the human body . They include: lactic acid (lacto-) bacteria, bifidobacteria, yeast. In the intestines of a healthy person, there is usually about 1-1.5 kg of probiotics - this amount is a guarantee of the full functioning of all systems and organs, as well as immunity). However, according to statistics, a large part of the healthy microflora in the human body is replaced by pathogenic ones, so in fact only 1/10 of the norm of beneficial bacteria is present .

Functions of probiotics:

  • Strengthening the immune system.
  • Stimulation of digestion.
  • Formation of vitamins K and B.
  • Neutralization of the harmful effects of pathogenic bacteria , toxins and slags.
  • Neutralization of the negative effect of antibiotics.
  • Prevention and treatment of diarrhea.
  • Prevention and treatment of allergies.
  • Treatment of inflammatory processes.
  • Ensuring metabolism.
  • Prevention and control of infections.
  • Positive effect on skin condition.

Products containing probiotics:

  • Yogurt
  • Kefir.
  • Soft cheeses.
  • Ryazanka
  • sour cream
  • Cottage cheese
  • Tofu (or soy cheese).
  • Miso soup (miso is a fermented soybean product).
  • Sourdough bread.
  • Pickled cucumbers and tomatoes.
  • Fermented cabbage.
  • Soaked apples.
  • Artichokes.
  • Leeks.
  • Onions.
  • Banana.

The most effective is the consumption of probiotics, together with prebiotics, which, in turn, are not digested in the intestines, but provide favorable conditions for the growth of healthy microflora.



The main source of lactobacilli for the human body is fermented milk products. It is lactobacilli that are the first bacteria for a newborn, as he receives them from the mother's birth canal.

Functions of lactobacilli:

  • The conversion of lactose into lactic acid is the creation of favorable conditions for food digestion.
  • Prevention of intestinal diseases — lactobacilli are responsible for the formation of special substances with antibiotic properties that inhibit the development of putrefactive bacteria .
  • Prevention of cancerous oncological diseases - lactobacilli stop the action of enzymes that lead to the formation and development of cancer cells.
  • Strengthening immunity — lactobacilli provide the synthesis of vitamin K, riboflavin, thiamin, iron, iodine, calcium, and selenium.
  • Stimulation of metabolism and metabolism.

Products containing lactobacilli

Since lactobacilli are stimulators of lactic acid fermentation, they are used in the production of fermented milk products, so the following are rich in bacteria :

  • Yogurts.
  • Kefir.
  • Soft cheeses.
  • Ryazanka
  • sour cream
  • Sour cream.
  • Cottage cheese


Bifidobacteria are present in the human body in small quantities, they are concentrated mainly in the large intestine, forming the basis of its wall and cavity microflora. These beneficial bacteria suppress the development of putrefactive and disease-causing bacteria in the body.

Functions of bifidobacteria:

  • Prevention of allergic reactions.
  • Restoration of intestinal microflora.
  • Prevention of dysbiosis.
  • Lowering cholesterol.
  • Stimulation of excess weight loss.
  • Restoration of kidney and liver functionality.
  • Prevention of oncological diseases.
  • Stimulation and support of digestion.
  • Ensuring intestinal peristalsis.
  • Synthesis and assimilation of amino acids and vitamins.
  • Strengthening the immune system.
  • Flatulence warning.
  • Reducing the harmful effects of carcinogens.

Products containing bifidobacteria :

  • Kefir.
  • Ryazanka
  • sour cream
  • Cottage cheese
  • Sour cream.
  • Soft varieties of cheeses.
  • Other fermented milk products.


Prebiotics are the remains of nutrients that are not digested by stomach enzymes, because they are not absorbed by the upper parts of the digestive tract, getting to the lower ones, where they are "fed" by probiotics - this has a positive effect not only on the digestive tract, but also on the whole body.

Functions of prebiotics :

  • Creation of healthy intestinal microflora.
  • Strengthening the immune system.
  • Stimulation of intestinal peristalsis.
  • Stimulation of metabolism.
  • Strengthening the action of probiotics.

Products containing prebiotics :

  • Chicory root.
  • Raw Jerusalem artichoke.
  • Dandelion greens.
  • Raw asparagus.
  • Leeks.
  • Onions are onion.
  • Garlic.
  • Raw wheat bran.
  • Wheat flour.
  • Oat groats.
  • Cornflakes.
  • Strawberries.
  • Banana.
  • Beer.

Harmful bacteria

Harmful bacteria include:

  • Escherichia coli.
  • Protein bar.
  • Stick perfringens.
  • Salmonella.
  • Staphylococcus aureus.
  • Botulinum.
Escherichia coli

A rod -shaped bacterium (more than 100 species) that lives in the intestines of warm-blooded organisms (animals, humans, birds). It is characterized by resistance to adverse factors, is stored for a long time in water, soil, and on objects. It reproduces at room temperature, but the most favorable temperature is +37ºС. Dies within 15 minutes at +60ºС.

The most vulnerable to contamination are ready meals made from meat, fish, potatoes, salads, etc. Also, very often the source of poisoning is water, the bacterium lives in reservoirs.


Protein bar

This is a putrefactive bacterium . Resistant to drying, high salt concentration, heating up to +65ºС for 30 minutes. It can reproduce at a temperature from +6 to +40ºС, the most favorable — from +20 to +37ºС. The bacterium does not change the organoleptic properties of products during infection.

The main cause of contamination: the use of surfaces and utensils that were used for raw products for slicing ready-made products and vegetables.


Stick perfringens

A bacterium that lives in water, soil, and food. It reproduces at a temperature of +15ºС, the most optimal — from +37 to +45ºС. Dies in an acidic environment. The stick is resistant to heat.

Prepared meals, in particular meat, are especially vulnerable. To prevent contamination, meals that are prepared in advance must be cooled in time and stored in the refrigerator.



A rod -shaped bacterium that causes salmonellosis is severe food poisoning. The bacterium reproduces at room temperature, and +37ºС is the most favorable. Also, salmonella is resistant to low temperatures, it can survive even at -20ºС. The bacterium reproduces worse in a salty environment, and does not reproduce at all in an acidic environment. It dies when heated to 100ºС instantly, to 60ºС within an hour.

Salmonella bacteria is quite common in nature, it is carried by animals, birds (waterfowl), insects and rodents. Especially vulnerable are meat, dairy products, fish, eggs. Salmonella does not change the properties of contaminated products.

You can prevent contamination of products with bacteria as follows:

  • Thoroughly wash fresh vegetables and fruits, greens before consumption.
  • Subject products to long-term heat treatment.
  • Store raw foods and ready meals separately.
  • Ready-made dishes, in particular, reheated ones should be stored for a minimum time.
Staphylococcus aureus

A bacterium that causes sore throat, inflammation, purulent skin diseases. It is constantly present on the skin, in the nasal and oral cavities of a person, and in the air. When it gets on food products, the bacterium develops rapidly and releases a large amount of toxin. The most favorable temperature for the development of bacteria is from +30 to +37ºС, however, it retains its viability even at +15-20ºС. Also, staphylococcus is resistant to drying and freezing. The bacterium dies when heated for 30 minutes to +80ºС. However, to neutralize the poison, it is necessary to heat it to +100ºС for 1.5-2 hours. Also, the development of bacteria stops in an acidic environment, but the poison remains.

Various products are susceptible to staphylococcus poison: fish, meat, vegetables, confectionery. The bacterium does not change their organoleptic properties. To prevent contamination of products with staphylococcus, it is necessary to observe the rules of personal hygiene, and also to store products in closed containers at a temperature of +2-4ºС.



The bacterium that causes the most severe food poisoning is botulism. The botulinum bacillus lives in the intestines of animals, humans, fish and birds, and is also present in water bodies, soil, on fruits and vegetables. The bacterium is very resistant to the influence of the external environment: it can develop without air access, it does not die during freezing and canning. However, high temperatures are destructive for botulinus: the bacterium dies when boiled for 15 minutes, when heated for 30 minutes to +80ºС, and meat and fish should be boiled for an hour. Heat treatment of products is the main method of preventing botulism.

The most vulnerable to bacterial contamination are canned foods, in particular, homemade ones: pickled mushrooms and vegetables, canned meat and fish, as well as ham, salted and dried fish. Botulinum does not change the organoleptic properties of products. Rare signs of infection can be: swelling of cans with canned goods, a faint smell of rancid fat, very rarely - softening and discoloration of products.

The main measures to prevent bacterial infection are:

  • Use of fresh and good quality products.
  • Their thorough processing.
  • Cold storage of canned goods.
  • 1.2-1.8% acetic acid in the marinade suppresses the reproduction of botulinum.


Spread of bacteria (PREMIUM)

Bacteria can get on food products in the following ways:

  • Dirty hands;
  • Purulent cuts, ulcers and burns;
  • Dirty work surfaces and equipment;
  • Air flow;
  • Contaminated or contaminated water;
  • Birds, rodents, insects;
  • Pets;
  • Food waste not removed on time.

Bacteria reproduce by fission. Under favorable conditions, the number of bacteria doubles every 20 minutes, that is, in 6 hours one bacterium can grow to about a million. Favorable conditions for the development of bacteria : heat, humidity, nutrient environment. Bacteria cannot multiply without moisture . Contaminated food causes food poisoning of varying severity.

The most vulnerable to bacterial infection are:

  • Broths, soups, sauces.
  • Dairy products and dishes.
  • Meat products and dishes.
  • Eggs, dishes made from eggs.
  • Products that underwent manual processing.
  • Reheated food.

Almost all bacteria die when exposed to high temperatures — heat treatment is the main means of preventing food poisoning from contaminated products.

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