A freezer can kill bacteria
As in private households, frozen foods are also safe products in communal catering with regard to food hygiene and safety over a longer period of time
- Shock freezing and storage at temperatures of at least -18 ° C and below, largely all microbiological processes that lead to food spoilage or the formation of harmful substances such as microbially produced toxins are inhibited.
- some microorganisms and parasites are already killed by the freezing.
- A large part of the germs on the surface of food can be killed by brief heating before flash freezing, e.g. by blanching vegetables or briefly pre-cooking ready-made meals.
- The frozen food is protected against dirt and microbial contamination through professional packaging.
Useful and unwanted germs on foodIt is impossible to imagine food production without lactic acid bacteria in sauerkraut production, baker's yeast in cakes or brewer's yeast in beer production.
However, there are also microorganisms that can spoil food or cause disease, or cause food infections or food poisoning. That is why food requires particular care when handling and preparing it in the kitchen. If kitchen hygiene is inadequate, food spoilage caused by bacteria or contamination with pathogenic germs can very quickly occur.
With germs, the one Food spoilage cause noticeable changes in color, surface, consistency, smell or taste of the food concerned.
Food infections are caused by pathogenic microorganisms themselves and Food poisoning caused by toxins (= poisonous substances) formed by pathogenic microorganisms. Both can cause serious gastrointestinal disorders. Infection or poisoning by pathogenic germs can be life-threatening for some groups of people such as children, the elderly or people with a weak immune system. Pathogenic germs include salmonella, listeria, staphylococci, clostridia, enterobacteriaceae (including EHEC) or campylobacter.
The germs often get onto food through inadequate kitchen hygiene. The main risk of transmission is food that is consumed raw, e.g. fresh sausage, raw milk and raw milk products, salads, raw fruit or vegetables, as well as food that has not been sufficiently heated, e.g. insufficiently cooked meat.
Can freezing kill parasites in food?As with microorganisms, deep freezing is one of the best ways to reduce parasitic dangers when used properly.
Animal products in particular can be affected by parasites that are harmful to human health. Under certain circumstances, harmful parasites such as trichinae, fins, toxoplasms, sarcosporidia or nematodes can get into the food. Freezing is one way to kill them off.
Microorganisms like it warmIn small numbers, microorganisms are often unavoidable on food. It only becomes dangerous when infectious agents are given the opportunity to multiply through favorable conditions. Microorganisms only have an opportunity to multiply if they find nutrients, sufficient moisture and temperatures that are comfortable for them.
Microbial metabolic processes are highly dependent on the water available in the food and on the product temperature. That is why lowering the temperature is one of the most important measures to reduce or inhibit microbial growth.
Can germs and bacteria be killed by deep freezing?The process of deep freezing deactivates or even kills microorganisms on the food. The pH value of the food has an influence on the survival rate of microorganisms on frozen products, so low pH values reduce the resistance of bacteria to cold. However, there are also ingredients in food that have a protective effect on microorganisms against the cold. These include, for example, milk proteins, salts (especially phosphate), peptides and amino acids, starch or egg yolks. The number of surviving microorganisms can therefore vary depending on the composition of the food. On average, a survival rate of between 10 and 50% can be expected.
Some germs that belong to the so-called gram-negative species, such as Pseudomonadaceae and pathogenic, i.e. disease-causing germs such as salmonella and shigella, are very sensitive to freezing. Listeria, which are often found on meat, fish and raw milk products, survive longer storage times. Most gram-positive microorganisms such as staphylococci are also less sensitive to freezing. Spores formed by some microorganisms are also largely freeze-resistant and can survive freezing temperatures.
In addition to the type of germ and the quality of the food, the thawing process has an impact on the survival rate of microorganisms. Rapid thawing of food damages the bacteria more than slow thawing.
Please note: After thawing, the surviving microorganisms multiply on frozen food just as quickly as on fresh products!
Food-associated virus hazardViruses such as noroviruses, rotaviruses, adenoviruses, the hepatitis A virus or hepatitis E virus can be transmitted through food and cause various diseases. The viruses usually come to the food through external influences such as smear infection through faeces due to inadequate personal hygiene, water contaminated with faeces or contaminated surfaces, but they do not multiply on it. A common viral infection is observed through food contaminated with noroviruses, which lead to gastrointestinal infections with nausea, vomiting and severe diarrhea. Food contaminated with the hepatitis A virus can cause liver inflammation if consumed.
The danger with food-associated viruses is that they are basically very infectious and can be contagious even in small quantities. In the acute phase, sick people excrete large amounts of viruses, but even after the infection has subsided, those affected can remain so-called “excretors” for up to two weeks or longer. The viruses can be found in food, water and on various surfaces such as B. outlast door handles, light switches or countertops. If the food is contaminated by viruses, even freezer temperatures of -18 ° C and colder cannot affect it. Adequate personal and environmental hygiene in the kitchen and cold rooms is therefore particularly important.
The virus can also be transmitted directly from person to person through droplet infection. In the kitchen or in the production plant, however, the food is usually contaminated during its preparation when sick employees excrete infectious viruses and hygiene standards are not adequately observed. Due to the high risk of infection, communal catering facilities such as hospitals, old people's homes or day-care centers are often affected by large outbreaks of viruses.
To ensure that outbreaks of disease can be prevented in principle, the kitchen staff must strictly adhere to the hygiene rules when handling food. The Infection Protection Act also stipulates that sick people are not allowed to produce, treat or market food.
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